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Posted to notifications@freemarker.apache.org by dd...@apache.org on 2017/03/15 21:19:37 UTC
[40/51] [partial] incubator-freemarker-site git commit: 2.3.26-voting
docs, removed nightly
http://git-wip-us.apache.org/repos/asf/incubator-freemarker-site/blob/a4004324/builds/2.3.26-nightly/dgui_template_exp.html
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-<div class="col-right"><div class="page-content"><div class="page-title"><div class="pagers top"><a class="paging-arrow previous" href="dgui_template_directives.html"><span>Previous</span></a><a class="paging-arrow next" href="dgui_template_valueinsertion.html"><span>Next</span></a></div><div class="title-wrapper">
-<h1 class="content-header header-section1" id="dgui_template_exp" itemprop="headline">Expressions</h1>
-</div></div><div class="page-menu">
-<div class="page-menu-title">Page Contents</div>
-<ul><li><a class="page-menu-link" href="#exp_cheatsheet" data-menu-target="exp_cheatsheet">Quick overview (cheat sheet)</a></li><li><a class="page-menu-link" href="#dgui_template_exp_direct" data-menu-target="dgui_template_exp_direct">Specify values directly</a><ul><li><a class="page-menu-link" href="#dgui_template_exp_direct_string" data-menu-target="dgui_template_exp_direct_string">Strings</a></li><li><a class="page-menu-link" href="#dgui_template_exp_direct_number" data-menu-target="dgui_template_exp_direct_number">Numbers</a></li><li><a class="page-menu-link" href="#dgui_template_exp_direct_boolean" data-menu-target="dgui_template_exp_direct_boolean">Booleans</a></li><li><a class="page-menu-link" href="#dgui_template_exp_direct_seuqence" data-menu-target="dgui_template_exp_direct_seuqence">Sequences</a></li><li><a class="page-menu-link" href="#dgui_template_exp_direct_ranges" data-menu-target="dgui_template_exp_direct_ranges">Ranges</a></li><li><a class="page-menu-link" href="#d
gui_template_exp_direct_hash" data-menu-target="dgui_template_exp_direct_hash">Hashes</a></li></ul></li><li><a class="page-menu-link" href="#dgui_template_exp_var" data-menu-target="dgui_template_exp_var">Retrieving variables</a><ul><li><a class="page-menu-link" href="#dgui_template_exp_var_toplevel" data-menu-target="dgui_template_exp_var_toplevel">Top-level variables</a></li><li><a class="page-menu-link" href="#dgui_template_exp_var_hash" data-menu-target="dgui_template_exp_var_hash">Retrieving data from a hash</a></li><li><a class="page-menu-link" href="#dgui_template_exp_var_sequence" data-menu-target="dgui_template_exp_var_sequence">Retrieving data from a sequence</a></li><li><a class="page-menu-link" href="#dgui_template_exp_var_special" data-menu-target="dgui_template_exp_var_special">Special variables</a></li></ul></li><li><a class="page-menu-link" href="#dgui_template_exp_stringop" data-menu-target="dgui_template_exp_stringop">String operations</a><ul><li><a class="page-men
u-link" href="#dgui_template_exp_stringop_interpolation" data-menu-target="dgui_template_exp_stringop_interpolation">Interpolation and concatenation</a></li><li><a class="page-menu-link" href="#dgui_template_exp_get_character" data-menu-target="dgui_template_exp_get_character">Getting a character</a></li><li><a class="page-menu-link" href="#dgui_template_exp_stringop_slice" data-menu-target="dgui_template_exp_stringop_slice">String slicing (substrings)</a></li></ul></li><li><a class="page-menu-link" href="#dgui_template_exp_sequenceop" data-menu-target="dgui_template_exp_sequenceop">Sequence operations</a><ul><li><a class="page-menu-link" href="#dgui_template_exp_sequenceop_cat" data-menu-target="dgui_template_exp_sequenceop_cat">Concatenation</a></li><li><a class="page-menu-link" href="#dgui_template_exp_seqenceop_slice" data-menu-target="dgui_template_exp_seqenceop_slice">Sequence slicing</a></li></ul></li><li><a class="page-menu-link" href="#dgui_template_exp_hashop" data-menu-ta
rget="dgui_template_exp_hashop">Hash operations</a><ul><li><a class="page-menu-link" href="#dgui_template_exp_hashop_cat" data-menu-target="dgui_template_exp_hashop_cat">Concatenation</a></li></ul></li><li><a class="page-menu-link" href="#dgui_template_exp_arit" data-menu-target="dgui_template_exp_arit">Arithmetical calculations</a></li><li><a class="page-menu-link" href="#dgui_template_exp_comparison" data-menu-target="dgui_template_exp_comparison">Comparison</a></li><li><a class="page-menu-link" href="#dgui_template_exp_logicalop" data-menu-target="dgui_template_exp_logicalop">Logical operations</a></li><li><a class="page-menu-link" href="#dgui_template_exp_builtin" data-menu-target="dgui_template_exp_builtin">Built-ins</a></li><li><a class="page-menu-link" href="#dgui_template_exp_methodcall" data-menu-target="dgui_template_exp_methodcall">Method call</a></li><li><a class="page-menu-link" href="#dgui_template_exp_missing" data-menu-target="dgui_template_exp_missing">Handling miss
ing values</a><ul><li><a class="page-menu-link" href="#dgui_template_exp_missing_default" data-menu-target="dgui_template_exp_missing_default">Default value operator</a></li><li><a class="page-menu-link" href="#dgui_template_exp_missing_test" data-menu-target="dgui_template_exp_missing_test">Missing value test operator</a></li></ul></li><li><a class="page-menu-link" href="#dgui_template_exp_assignment" data-menu-target="dgui_template_exp_assignment">Assignment Operators</a></li><li><a class="page-menu-link" href="#dgui_template_exp_parentheses" data-menu-target="dgui_template_exp_parentheses">Parentheses</a></li><li><a class="page-menu-link" href="#dgui_template_exp_whitespace" data-menu-target="dgui_template_exp_whitespace">White-space in expressions</a></li><li><a class="page-menu-link" href="#dgui_template_exp_precedence" data-menu-target="dgui_template_exp_precedence">Operator precedence</a></li></ul> </div><p>When you supply values for interpolations or directive
- parameters you can use variables or more complex expressions. For
- example, if x is the number 8 and y is 5, the value of <code class="inline-code">(x +
- y)/2</code> resolves to the numerical value 6.5.</p><p>Before we go into details, let's see some concrete
- examples:</p><ul>
- <li>
- <p>When you supply value for interpolations: The usage of
- interpolations is
- <code class="inline-code">${<em class="code-color">expression</em>}</code> where
- expression gives the value you want to insert into the output as
- text. So <code class="inline-code">${(5 + 8)/2}</code> prints "6.5"
- to the output (or possibly "6,5" if the language of
- your output is not US English).</p>
- </li>
-
- <li>
- <p>When you supply a value for the directive parameter: You
- have already seen the <code class="inline-code">if</code> directive in the
- Getting Started section. The syntax of this directive is:
- <code class="inline-code"><#if
- <em class="code-color">expression</em>><em class="code-color">...</em></#if></code>.
- The expression here must evaluate to a boolean value. For example
- in <code class="inline-code"><#if 2 < 3></code> the <code class="inline-code">2 <
- 3</code> (2 is less than 3) is an expression which evaluates to
- <code class="inline-code">true</code>.</p>
- </li>
- </ul>
-
-
-
-
-<h2 class="content-header header-section2" id="exp_cheatsheet">Quick overview (cheat sheet)</h2>
-
-
- <p>This is a reminder for those of you who already know
- FreeMarker or are just experienced programmers:</p>
-
- <ul>
- <li>
- <a href="#dgui_template_exp_direct">Specify values
- directly</a>
-
- <ul>
- <li>
- <a href="#dgui_template_exp_direct_string">Strings</a>:
- <code class="inline-code">"Foo"</code> or <code class="inline-code">'Foo'</code> or
- <code class="inline-code">"It's \"quoted\""</code> or <code class="inline-code">'It\'s
- "quoted"'</code> or
- <code class="inline-code">r"C:\raw\string"</code>
- </li>
-
- <li>
- <a href="#dgui_template_exp_direct_number">Numbers</a>:
- <code class="inline-code">123.45</code>
- </li>
-
- <li>
- <a href="#dgui_template_exp_direct_boolean">Booleans</a>:
- <code class="inline-code">true</code>, <code class="inline-code">false</code>
- </li>
-
- <li>
- <a href="#dgui_template_exp_direct_seuqence">Sequences</a>:
- <code class="inline-code">["foo", "bar", 123.45]</code>; Ranges:
- <code class="inline-code">0..9</code>, <code class="inline-code">0..<10</code> (or
- <code class="inline-code">0..!10</code>), <code class="inline-code">0..</code>
- </li>
-
- <li>
- <a href="#dgui_template_exp_direct_hash">Hashes</a>:
- <code class="inline-code">{"name":"green�mouse",
- "price":150}</code>
- </li>
- </ul>
- </li>
-
- <li>
- <a href="#dgui_template_exp_var">Retrieving
- variables</a>
-
- <ul>
- <li>
- <a href="#dgui_template_exp_var_toplevel">Top-level
- variables</a>: <code class="inline-code">user</code>
- </li>
-
- <li>
- <a href="#dgui_template_exp_var_hash">Retrieving
- data from a hash</a>: <code class="inline-code">user.name</code>,
- <code class="inline-code">user["name"]</code>
- </li>
-
- <li>
- <a href="#dgui_template_exp_var_sequence">Retrieving data
- from a sequence</a>:
- <code class="inline-code">products[5]</code>
- </li>
-
- <li>
- <a href="#dgui_template_exp_var_special">Special
- variable</a>: <code class="inline-code">.main</code>
- </li>
- </ul>
- </li>
-
- <li>
- <a href="#dgui_template_exp_stringop">String
- operations</a>
-
- <ul>
- <li>
- <a href="#dgui_template_exp_stringop_interpolation">Interpolation
- and concatenation</a>:
- <code class="inline-code">"Hello�${user}!"</code> (or <code class="inline-code">"Hello
- "�+�user + "!"</code>)
- </li>
-
- <li>
- <a href="#dgui_template_exp_get_character">Getting a
- character</a>: <code class="inline-code">name[0]</code>
- </li>
-
- <li>
- <a href="#dgui_template_exp_stringop_slice">String
- slice:</a> Inclusive end: <code class="inline-code">name[0..4]</code>,
- Exclusive end: <code class="inline-code">name[0..<5]</code>,
- Length-based (lenient): <code class="inline-code">name[0..*5]</code>,
- Remove starting: <code class="inline-code">name[5..]</code>
- </li>
- </ul>
- </li>
-
- <li>
- <a href="#dgui_template_exp_sequenceop">Sequence
- operations</a>
-
- <ul>
- <li>
- <a href="#dgui_template_exp_sequenceop_cat">Concatenation</a>:
- <code class="inline-code">users + ["guest"]</code>
- </li>
-
- <li>
- <a href="#dgui_template_exp_seqenceop_slice">Sequence
- slice</a>: Inclusive end:
- <code class="inline-code">products[20..29]</code>, Exclusive end:
- <code class="inline-code">products[20..<30]</code>, Length-based
- (lenient): <code class="inline-code">products[20..*10]</code>, Remove
- starting: <code class="inline-code">products[20..]</code>
- </li>
- </ul>
- </li>
-
- <li>
- <a href="#dgui_template_exp_hashop">Hash
- operations</a>
-
- <ul>
- <li>
- <a href="#dgui_template_exp_hashop_cat">Concatenation</a>:
- <code class="inline-code">passwords + { "joe": "secret42" }</code>
- </li>
- </ul>
- </li>
-
- <li>
- <a href="#dgui_template_exp_arit">Arithmetical
- calculations</a>: <code class="inline-code">(x * 1.5 + 10) / 2 - y %
- 100</code>
- </li>
-
- <li>
- <a href="#dgui_template_exp_comparison">Comparison</a>:
- <code class="inline-code">x�==�y</code>, <code class="inline-code">x�!=�y</code>,
- <code class="inline-code">x�<�y</code>, <code class="inline-code">x�>�y</code>,
- <code class="inline-code">x�>=�y</code>, <code class="inline-code">x�<=�y</code>,
- <code class="inline-code">x�lt�y</code>, <code class="inline-code">x�lte�y</code>,
- <code class="inline-code">x gt y</code>, <code class="inline-code">x gte y</code>,
- ...etc.
- </li>
-
- <li>
- <a href="#dgui_template_exp_logicalop">Logical
- operations</a>: <code class="inline-code">!registered && (firstVisit
- || fromEurope)</code>
- </li>
-
- <li>
- <a href="#dgui_template_exp_builtin">Built-ins</a>:
- <code class="inline-code">name?upper_case</code>,
- <code class="inline-code">path?ensure_starts_with('/')</code>
- </li>
-
- <li>
- <a href="#dgui_template_exp_methodcall">Method
- call</a>: <code class="inline-code">repeat("What", 3)</code>
- </li>
-
- <li>
- <a href="#dgui_template_exp_missing">Missing value
- handler operators</a>:
-
- <ul>
- <li>
- <a href="#dgui_template_exp_missing_default">Default
- value</a>: <code class="inline-code">name!"unknown"</code> or
- <code class="inline-code">(user.name)!"unknown"</code> or
- <code class="inline-code">name!</code> or
- <code class="inline-code">(user.name)!</code>
- </li>
-
- <li>
- <a href="#dgui_template_exp_missing_test">Missing
- value test</a>: <code class="inline-code">name??</code> or
- <code class="inline-code">(user.name)??</code>
- </li>
- </ul>
- </li>
-
- <li>
- <a href="#dgui_template_exp_assignment">Assignment
- operators</a>: <code class="inline-code">=</code>, <code class="inline-code">+=</code>,
- <code class="inline-code">-=</code>, <code class="inline-code">*=</code>,
- <code class="inline-code">/=</code>, <code class="inline-code">%=</code>,
- <code class="inline-code">++</code>, <code class="inline-code">--</code>
- </li>
- </ul>
-
- <p>See also: <a href="#dgui_template_exp_precedence">Operator
- precedence</a></p>
-
-
-
-
-
-<h2 class="content-header header-section2" id="dgui_template_exp_direct">Specify values directly</h2>
-
-
-
-
-
-
- <p>Often you want to specify a value directly and not as a result
- of some calculations.</p>
-
-
-
-
-
-
-<h3 class="content-header header-section3" id="dgui_template_exp_direct_string">Strings</h3>
-
-
-
-
- <p>To specify a string value directly you give the text in
- quotation marks, e.g.: <code class="inline-code">"some text"</code> or in
- apostrophe-quote, e.g. <code class="inline-code">'some text'</code>. The two
- forms are equivalent. If the text itself contains the character
- used for the quoting (either <code class="inline-code">"</code> or
- <code class="inline-code">'</code>) or backslashes, you have to precede them
- with a backslash; this is called escaping. You can type any other
- character, including <a href="gloss.html#gloss.lineBreak">line
- breaks</a>, in the text directly. Example:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-template">${"It's \"quoted\" and
-this is a backslash: \\"}
-
-${'It\'s "quoted" and
-this is a backslash: \\'}</pre></div>
-
- <p>will print:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-output">It's "quoted" and
-this is a backslash: \
-
-It's "quoted" and
-this is a backslash: \</pre></div>
-
- <div class="callout note">
- <strong class="callout-label">Note:</strong>
-
- <p>Of course, you could simply type the above text into the
- template, without using
- <code class="inline-code">${<em class="code-color">...</em>}</code>. But we do
- it here just for the sake of example, to demonstrate
- expressions.</p>
- </div>
-
-
- <a name="topic.escapeSequence"></a>
-
-
-
- <p>This is the list of all supported escape sequences. All
- other usage of backlash in string literals is an error and any
- attempt to use the template will fail.</p>
-
- <div class="table-responsive">
- <table class="table">
-
- <thead>
- <tr>
- <th>Escape sequence</th>
-
-
- <th>Meaning</th>
-
- </tr>
-
- </thead>
-
-
- <tbody>
- <tr>
- <td><code class="inline-code">\"</code></td>
-
-
- <td>Quotation mark (u0022)</td>
-
- </tr>
-
-
- <tr>
- <td><code class="inline-code">\'</code></td>
-
-
- <td>Apostrophe (a.k.a. apostrophe-quote) (u0027)</td>
-
- </tr>
-
-
- <tr>
- <td><code class="inline-code">\{</code></td>
-
-
- <td>Opening curly brace: <code class="inline-code">{</code></td>
-
- </tr>
-
-
- <tr>
- <td><code class="inline-code">\\</code></td>
-
-
- <td>Back slash (u005C)</td>
-
- </tr>
-
-
- <tr>
- <td><code class="inline-code">\n</code></td>
-
-
- <td>Line feed (u000A)</td>
-
- </tr>
-
-
- <tr>
- <td><code class="inline-code">\r</code></td>
-
-
- <td>Carriage return (u000D)</td>
-
- </tr>
-
-
- <tr>
- <td><code class="inline-code">\t</code></td>
-
-
- <td>Horizontal tabulation (a.k.a. tab) (u0009)</td>
-
- </tr>
-
-
- <tr>
- <td><code class="inline-code">\b</code></td>
-
-
- <td>Backspace (u0008)</td>
-
- </tr>
-
-
- <tr>
- <td><code class="inline-code">\f</code></td>
-
-
- <td>Form feed (u000C)</td>
-
- </tr>
-
-
- <tr>
- <td><code class="inline-code">\l</code></td>
-
-
- <td>Less-than sign: <code class="inline-code"><</code></td>
-
- </tr>
-
-
- <tr>
- <td><code class="inline-code">\g</code></td>
-
-
- <td>Greater-than sign: <code class="inline-code">></code></td>
-
- </tr>
-
-
- <tr>
- <td><code class="inline-code">\a</code></td>
-
-
- <td>Ampersand: <code class="inline-code">&</code></td>
-
- </tr>
-
-
- <tr>
- <td><code class="inline-code">\x<em class="code-color">Code</em></code></td>
-
-
- <td>Character given with its hexadecimal <a href="gloss.html#gloss.unicode">Unicode</a> code (<a href="gloss.html#gloss.UCS">UCS</a> code)</td>
-
- </tr>
-
- </tbody>
-
- </table>
- </div>
-
-
- <p>The <code class="inline-code"><em class="code-color">Code</em></code> after
- the <code class="inline-code">\x</code> is 1 to 4 hexadecimal digits. For
- example this all put a copyright sign into the string:
- <code class="inline-code">"\xA9�1999-2001"</code>,
- <code class="inline-code">"\x0A9�1999-2001"</code>,
- <code class="inline-code">"\x00A9�1999-2001"</code>. When the character directly
- after the last hexadecimal digit can be interpreted as hexadecimal
- digit, you must use all 4 digits or else FreeMarker will
- misunderstand you.</p>
-
- <p>Note that the character sequence <code class="inline-code">${</code> (and
- <code class="inline-code">#{</code>) has special meaning. It's used to insert
- the value of expressions (typically: the value of variables, as in
- <code class="inline-code">"Hello�${user}!"</code>). This will be explained <a href="#dgui_template_exp_stringop_interpolation">later</a>.
- If you want to print <code class="inline-code">${</code> or
- <code class="inline-code">#{</code>, you should either use raw string literals
- as explained below, or escape the <code class="inline-code">{</code> like in
- <code class="inline-code">"foo $\{bar}"</code>.</p>
-
-
-
- <p>A special kind of string literals is the raw string
- literals. In raw string literals, backslash and
- <code class="inline-code">${</code> have no special meaning, they are considered
- as plain characters. To indicate that a string literal is a raw
- string literal, you have to put an <code class="inline-code">r</code> directly
- before the opening quotation mark or apostrophe-quote.
- Example:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-template">${r"${foo}"}
-${r"C:\foo\bar"}</pre></div>
-
- <p>will print:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-output">${foo}
-C:\foo\bar</pre></div>
-
-
-
-
-
-
-
-<h3 class="content-header header-section3" id="dgui_template_exp_direct_number">Numbers</h3>
-
-
-
-
- <p>To specify a numerical value directly you type the number
- without quotation marks. You have to use the dot as your decimal
- separator and must not use any grouping separator symbols. You can
- use <code class="inline-code">-</code> or <code class="inline-code">+</code> to indicate the
- sign (<code class="inline-code">+</code> is redundant). Scientific notation is
- not yet supported (so <code class="inline-code">1E3</code> is wrong). Also, you
- cannot omit the 0 before the decimal separator (so
- <code class="inline-code">.5</code> is wrong).</p>
-
- <p>Examples of valid number literals: <code class="inline-code">0.08</code>,
- <code class="inline-code">-5.013</code>, <code class="inline-code">8</code>,
- <code class="inline-code">008</code>, <code class="inline-code">11</code>,
- <code class="inline-code">+11</code></p>
-
- <p>Note that numerical literals like <code class="inline-code">08</code>,
- <code class="inline-code">+8</code>, <code class="inline-code">8.00</code> and
- <code class="inline-code">8</code> are totally equivalent as they all symbolize
- the number eight. Thus, <code class="inline-code">${08}</code>,
- <code class="inline-code">${+8}</code>, <code class="inline-code">${8.00}</code> and
- <code class="inline-code">${8}</code> will all print exactly same.</p>
-
-
-
-
-
-
-
-<h3 class="content-header header-section3" id="dgui_template_exp_direct_boolean">Booleans</h3>
-
-
-
-
-
-
- <p>To specify a boolean value you write <code class="inline-code">true</code>
- or <code class="inline-code">false</code>. Don't use quotation marks.</p>
-
-
-
-
-
-
-
-<h3 class="content-header header-section3" id="dgui_template_exp_direct_seuqence">Sequences</h3>
-
-
-
-
-
-
-
-
-
-
- <p>To specify a literal sequence, you list the <a href="dgui_quickstart_datamodel.html#topic.dataModel.subVar">sub variables</a> separated by
- commas, and put the whole list into square brackets. For
- example:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-template"><#list <strong>["foo", "bar", "baz"]</strong> as x>
-${x}
-</#list></pre></div>
-
- <p>will print:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-output">foo
-bar
-baz
- </pre></div>
-
- <p>The items in the list are expressions, so you can do this
- for example: <code class="inline-code">[2 + 2, [1, 2, 3, 4], "foo"]</code>. Here
- the first subvariable will be the number 4, the second will be
- another sequence, and the third subvariable will be the string
- "foo".</p>
-
-
-
-
-
-
-
-<h3 class="content-header header-section3" id="dgui_template_exp_direct_ranges">Ranges</h3>
-
-
- <p>Ranges are just sequences, but they are created by
- specifying what range of whole numbers they contain, instead of
- specifying their items one by one. For example,
- <code class="inline-code">0..<m</code>, assuming the <code class="inline-code">m</code>
- variable stores 5, will give a sequence that contains <code class="inline-code">[0,
- 1, 2, 3, 4]</code>. Ranges are primarily used for iterating
- over a range of numbers with <code class="inline-code"><#list
- <em class="code-color">...</em>></code> and for <a href="#dgui_template_exp_seqenceop_slice">slicing
- sequences</a> and <a href="#dgui_template_exp_stringop_slice">slicing
- strings</a>.</p>
-
- <p>The generic forms of range expressions are (where
- <code class="inline-code"><em class="code-color">start</em></code> and
- <code class="inline-code"><em class="code-color">end</em></code> can be any
- expression that evaluates to a number):</p>
-
- <ul>
- <li>
- <p><code class="inline-code"><em class="code-color">start</em>..<em class="code-color">end</em></code>:
- Range with inclusive end. For example, <code class="inline-code">1..4</code>
- gives <code class="inline-code">[1, 2, 3, 4]</code>, and
- <code class="inline-code">4..1</code> gives <code class="inline-code">[4, 3, 2, 1]</code>.
- Beware, ranges with inclusive end never give an empty
- sequence, so <code class="inline-code">0..length-1</code> is
- <em>WRONG</em>, because when length is
- <code class="inline-code">0</code> it gives <code class="inline-code">[0,
- -1]</code>.</p>
- </li>
-
- <li>
- <p><code class="inline-code"><em class="code-color">start</em>..<<em class="code-color">end</em></code>
- or
- <code class="inline-code"><em class="code-color">start</em>..!<em class="code-color">end</em></code>:
- Range with exclusive end. For example,
- <code class="inline-code">1..<4</code> gives <code class="inline-code">[1, 2,
- 3]</code>, <code class="inline-code">4..<1</code> gives <code class="inline-code">[4,
- 3, 2]</code>, and <code class="inline-code">1..<1</code> gives
- <code class="inline-code">[]</code>. Note the last example; the result can
- be an empty sequence. There's no difference between
- <code class="inline-code">..<</code> and <code class="inline-code">..!</code>; the last
- form is used in applications where using the
- <code class="inline-code"><</code> character causes problems (for HTML
- editors and such).</p>
- </li>
-
- <li>
- <p><code class="inline-code"><em class="code-color">start</em>..*<em class="code-color">length</em></code>:
- Length limited range. For example, <code class="inline-code">10..*4</code>
- gives <code class="inline-code">[10, 11, 12, 13]</code>,
- <code class="inline-code">10..*-4</code> gives <code class="inline-code">[10, 9, 8,
- 7]</code>, and <code class="inline-code">10..*0</code> gives
- <code class="inline-code">[]</code>. When these kind of ranges are used for
- slicing, the slice will end without error if the end of the
- sliced sequence or string is reached before the specified
- range length was reached; see <a href="#dgui_template_exp_seqenceop_slice">slicing
- sequences</a> for more.</p>
-
- <div class="callout note">
- <strong class="callout-label">Note:</strong>
-
- <p>Length limited ranges were introduced in FreeMarker
- 2.3.21.</p>
- </div>
-
- </li>
-
- <li>
- <p><code class="inline-code"><em class="code-color">start</em>..</code>:
- Right-unbounded range. This are like length limited ranges
- with infinite length. For example <code class="inline-code">1..</code> gives
- <code class="inline-code">[1, 2, 3, 4, 5, 6, ... ]</code>, up to infinity.
- Be careful when processing (like listing) such ranges, as
- processing all items of it it would take forever or until the
- application runs out of memory and crashes. Just like with
- length limited ranges, when these kind of ranges are used for
- slicing, the slice will end when the end of the sliced
- sequence or string is reached.</p>
-
- <div class="callout warning">
- <strong class="callout-label">Warning!</strong>
-
- <p>Right-unbounded ranges before FreeMarker 2.3.21 were
- only used for slicing, and behaved like an empty sequence
- for other purposes. To activate the new behavior, it's not
- enough to use FreeMarker 2.3.21, the programmer also have to
- set the <code class="inline-code">incompatible_improvements</code>
- configuration setting to at least 2.3.21.</p>
- </div>
-
- </li>
- </ul>
-
- <p>Further notes on ranges:</p>
-
- <ul>
- <li>
- <p>Range expressions themselves don't have square brackets,
- for example, you write <code class="inline-code"><#assign myRange =
- 0..<x</code>, NOT <code class="inline-code"><#assign myRange =
- [0..<x]></code>. The last would create a sequence
- that contains an item that's a range. The square brackets are
- part of the slicing syntax, like
- <code class="inline-code"><em class="code-color">seq</em>[<em class="code-color">myRange</em>]</code>.</p>
- </li>
-
- <li>
- <p>You can write arithmetical expression on the sides of
- the <code class="inline-code">..</code> without parenthesis, like <code class="inline-code">n
- + 1 ..< m / 2 - 1</code>.</p>
- </li>
-
- <li>
- <p><code class="inline-code">..</code>, <code class="inline-code">..<</code>,
- <code class="inline-code">..!</code> and <code class="inline-code">..*</code> are
- operators, so you can't have space inside them. Like
- <code class="inline-code">n .. <m</code> is WRONG, but <code class="inline-code">n ..<
- m</code> is good.</p>
- </li>
-
- <li>
- <p>The reported size of right-unbounded ranges is
- 2147483647 (or 0 if
- <code class="inline-code">incompatible_improvements</code> is less than
- 2.3.21) due to a technical limitation (32 bits). However, when
- listing them, their actual size is infinite.</p>
- </li>
-
- <li>
- <p>Ranges don't really store the numbers they consist of,
- thus for example <code class="inline-code">0..1</code> and
- <code class="inline-code">0..100000000</code> is equally fast to create and
- takes the same amount of memory.</p>
- </li>
- </ul>
-
-
-
-
-
-
-
-<h3 class="content-header header-section3" id="dgui_template_exp_direct_hash">Hashes</h3>
-
-
-
-
-
-
- <p>To specify a hash in a template, you list the key/value
- pairs separated by commas, and put the list into curly brackets.
- The key and value within a key/value pair are separated with a
- colon. Here is an example: <code class="inline-code">{ "name": "green�mouse",
- "price": 150 }</code>. Note that both the names and the values
- are expressions. The keys must be strings. The values can be if
- any type.</p>
-
-
-
-
-
-
-<h2 class="content-header header-section2" id="dgui_template_exp_var">Retrieving variables</h2>
-
-
-
-
-
-
-
-<h3 class="content-header header-section3" id="dgui_template_exp_var_toplevel">Top-level variables</h3>
-
-
-
-
- <p>To access a top-level variable, you simply use the variable
- name. For example, the expression <code class="inline-code">user</code> will
- evaluate to the value of variable stored with name
- "user" in the root. So this will print what you store
- there:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-template">${user}</pre></div>
-
- <p>If there is no such top-level variable, then an error will
- result when FreeMarker tries to evaluate the expression, and it
- aborts template processing (unless programmers has configured
- FreeMarker differently).</p>
-
- <p>In this kind of expression, the variable name can only
- contain letters (including non-Latin letters), digits (including
- non-Latin digits), underline (<code class="inline-code">_</code>), dollar
- (<code class="inline-code">$</code>), at sign (<code class="inline-code">@</code>).
- Furthermore, the first character can't be a ASCII digit
- (<code class="inline-code">0</code>-<code class="inline-code">9</code>). Starting from
- FreeMarker 2.3.22, the variable name can also contain minus
- (<code class="inline-code">-</code>), dot (<code class="inline-code">.</code>), and colon
- (<code class="inline-code">:</code>) at any position, but these must be escaped
- with a preceding backslash (<code class="inline-code">\</code>), or else they
- would be interpreted as operators. For example, to read the
- variable whose name is "data-id", the expression is
- <code class="inline-code">data\-id</code>, as <code class="inline-code">data-id</code> would
- be interpreted as "data minus id". (Note that these
- escapes only work in identifiers, not in string literals.)</p>
-
-
-
-
-
-
-
-<h3 class="content-header header-section3" id="dgui_template_exp_var_hash">Retrieving data from a hash</h3>
-
-
-
-
-
-
- <p>If we already have a hash as a result of an expression, then
- we can get its subvariable with a dot and the name of the
- subvariable. Assume that we have this data-model:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-data-model">(root)
- |
- +- book
- | |
- | +- title = "Breeding green mouses"
- | |
- | +- author
- | |
- | +- name = "Julia Smith"
- | |
- | +- info = "Biologist, 1923-1985, Canada"
- |
- +- test = "title"</pre></div>
-
- <p>Now we can read the <code class="inline-code">title</code> with
- <code class="inline-code">book.title</code>, since the book expression will
- return a hash (as explained in the last chapter). Applying this
- logic further, we can read the name of the author with this
- expression: <code class="inline-code">book.author.name</code>.</p>
-
- <p>There is an alternative syntax if we want to specify the
- subvariable name with an expression:
- <code class="inline-code">book["title"]</code>. In the square brackets you can
- give any expression as long as it evaluates to a string. So with
- this data-model you can also read the title with
- <code class="inline-code">book[test]</code>. More examples; these are all
- equivalent: <code class="inline-code">book.author.name</code>,
- <code class="inline-code">book["author"].name</code>,
- <code class="inline-code">book.author.["name"]</code>,
- <code class="inline-code">book["author"]["name"]</code>.</p>
-
- <p>When you use the dot syntax, the same restrictions apply
- regarding the variable name as with top-level variables (name can
- contain only letters, digits, <code class="inline-code">_</code>,
- <code class="inline-code">$</code>, <code class="inline-code">@</code> but can't start with
- <code class="inline-code">0</code>-<code class="inline-code">9</code>, also starting from
- 2.3.22 you can also use <code class="inline-code">\-</code>,
- <code class="inline-code">\.</code> and <code class="inline-code">\:</code>). There are no
- such restrictions when you use the square bracket syntax, since
- the name is the result of an arbitrary expression. (Note, that to
- help the FreeMarker XML support, if the subvariable name is
- <code class="inline-code">*</code> (asterisk) or <code class="inline-code">**</code>, then you
- do not have to use square bracket syntax.)</p>
-
- <p>As with the top-level variables, trying to access a
- non-existent subvariable causes an error and aborts the processing
- of the template (unless programmers has configured FreeMarker
- differently).</p>
-
-
-
-
-
-
-
-<h3 class="content-header header-section3" id="dgui_template_exp_var_sequence">Retrieving data from a sequence</h3>
-
-
-
-
-
-
- <p>This is the same as for hashes, but you can use the square
- bracket syntax only, and the expression in the brackets must
- evaluate to a number, not a string. For example to get the name of
- the first animal of the <a href="dgui_datamodel_basics.html#example.stdDataModel">example data-model</a> (remember
- that the number of the first item is 0, not 1):
- <code class="inline-code">animals[0].name</code></p>
-
-
-
-
-
-
-
-<h3 class="content-header header-section3" id="dgui_template_exp_var_special">Special variables</h3>
-
-
-
-
- <p>Special variables are variables defined by the FreeMarker
- engine itself. To access them, you use the
- <code class="inline-code">.<em class="code-color">variable_name</em></code>
- syntax.</p>
-
- <p>Normally you don't need to use special variables. They are
- for expert users. The complete list of special variables can be
- found in the <a href="ref_specvar.html">reference</a>.</p>
-
-
-
-
-
-
-<h2 class="content-header header-section2" id="dgui_template_exp_stringop">String operations</h2>
-
-
-
-
-
-
-
-
-
-<h3 class="content-header header-section3" id="dgui_template_exp_stringop_interpolation">Interpolation and concatenation</h3>
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- <p>If you want to insert the value of an expression into a
- string, you can use
- <code class="inline-code">${<em class="code-color">...</em>}</code> (and the
- deprecated <code class="inline-code">#{<em class="code-color">...</em>}</code>)
- in string literals.
- <code class="inline-code">${<em class="code-color">...</em>}</code> in string
- literals <a href="dgui_template_valueinsertion.html">behaves
- similarly as in <span class="marked-text">text</span>
- sections</a> (so it goes through the same <em>locale
- sensitive</em> number and date/time formatting).</p>
-
- <p>Example (assume that user is "Big Joe"):</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-template"><#assign s = "Hello ${user}!">
-${s} <#-- Just to see what the value of s is --></pre></div>
-
- <p>This will print:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-output">Hello Big Joe!</pre></div>
-
- <div class="callout warning">
- <strong class="callout-label">Warning!</strong>
-
- <p>A frequent mistake of users is the usage of interpolations
- in places where they needn't/shouldn't/can't be used.
- Interpolations work <em>only</em> in <a href="dgui_template_overallstructure.html"><span class="marked-text">text</span> sections</a> (e.g.
- <code class="inline-code"><h1>Hello ${name}!</h1></code>) and in
- string literals (e.g. <code class="inline-code"><#include
- "/footer/${company}.html"></code>). A typical
- <em>WRONG</em> usage is <code class="inline-code"><#if
- ${big}>...</#if></code>, which will cause a
- syntactical error. You should simply write <code class="inline-code"><#if
- big>...</#if></code>. Also, <code class="inline-code"><#if
- "${big}">...</#if></code> is
- <em>WRONG</em>, since it converts the parameter
- value to string and the <code class="inline-code">if</code> directive wants a
- boolean value, so it will cause a runtime error.</p>
- </div>
-
-
- <p><a name="dgui_template_exp_stringop_concatenation"></a>Alternatively,
- you can use the <code class="inline-code">+</code> operator to achieve similar
- result:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-template"><#assign s = "Hello " + user + "!"></pre></div>
-
- <p>This gives the same result as the earlier example with the
- <code class="inline-code">${<em class="code-color">...</em>}</code>.</p>
-
- <div class="callout warning">
- <strong class="callout-label">Warning!</strong>
-
- <p>Because <code class="inline-code">+</code> follows similar rules as
- <code class="inline-code">${<em class="code-color">...</em>}</code>, the
- appended string is influenced by the <code class="inline-code">locale</code>,
- <code class="inline-code">number_format</code>,
- <code class="inline-code">date_format</code>, <code class="inline-code">time_format</code>,
- <code class="inline-code">datetime_format</code> and
- <code class="inline-code">boolean_format</code>, etc. settings, and thus the
- result targets humans and isn't in generally machine parseable.
- This mostly leads to problems with numbers, as many locales use
- grouping (thousands separators) by default, and so
- <code class="inline-code">"someUrl?id=" + id</code> becomes to something like
- <code class="inline-code">"someUrl?id=1�234"</code>. To prevent this, use the
- <code class="inline-code">?c</code> (for Computer audience) built-in, like in
- <code class="inline-code">"someUrl?id=" + id?c</code> or
- <code class="inline-code">"someUrl?id=${id?c}"</code>, which will evaluate to
- something like <code class="inline-code">"someUrl?id=1234"</code>, regardless
- of locale and format settings.</p>
- </div>
-
-
- <p>As when <code class="inline-code">${<em class="code-color">...</em>}</code>
- is used inside string <em>expressions</em> it's just a
- shorthand of using the <code class="inline-code">+</code> operator, <a href="dgui_misc_autoescaping.html">auto-escaping</a> is not
- applied on it.</p>
-
-
-
-
-
-
-
-<h3 class="content-header header-section3" id="dgui_template_exp_get_character">Getting a character</h3>
-
-
-
-
-
-
- <p>You can get a single character of a string at a given index
- similarly as you can <a href="#dgui_template_exp_var_sequence">read the subvariable of a
- sequence</a>, e.g. <code class="inline-code">user[0]</code>. The result will
- be a string whose length is 1; FTL doesn't have a separate
- character type. As with sequence sub variables, the index must be
- a number that is at least 0 and less than the length of the
- string, or else an error will abort the template
- processing.</p>
-
- <p>Since the sequence subvariable syntax and the character
- getter syntax clashes, you can use the character getter syntax
- only if the variable is not a sequence as well (which is possible
- because FTL supports multi-typed values), since in that case the
- sequence behavior prevails. (To work this around, you can use
- <a href="ref_builtins_string.html#ref_builtin_string_for_string">the
- <code>string</code> built-in</a>, e.g.
- <code class="inline-code">user?string[0]</code>. Don't worry if you don't
- understand this yet; built-ins will be discussed later.)</p>
-
- <p>Example (assume that user is "Big Joe"):</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-template">${user[0]}
-${user[4]}</pre></div>
-
- <p>will print (note that the index of the first character is
- 0):</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-output">B
-J</pre></div>
-
-
-
-
-
-
-
-<h3 class="content-header header-section3" id="dgui_template_exp_stringop_slice">String slicing (substrings)</h3>
-
-
-
-
-
-
-
-
-
-
- <p>You can a slice a string in the same way as you <a href="#dgui_template_exp_seqenceop_slice">slice a
- sequence</a> (see there), only here instead of sequence items
- you work with characters. Some differences are:</p>
-
- <ul>
- <li>
- <p>Decreasing ranges aren't allowed for string slicing.
- (That's because unlike sequences, you seldom if ever want to
- show a string reversed, so if that happens, that's almost
- always the result of an oversight.)</p>
- </li>
-
- <li>
- <p>If a value is both a string and a sequence (a
- multi-typed value), then slicing will slice the sequence
- instead of the string. When you are processing XML, such
- values are common. In such cases you can use
- <code class="inline-code"><em class="code-color">someXMLnode</em>?string[<em class="code-color">range</em>]</code>.</p>
- </li>
-
- <li>
- <p>There's a legacy bug where a range with
- <em>inclusive</em> end that's one less than the
- starting index and is non-negative (like in
- <code class="inline-code">"abc"[1..0]</code>) will give an empty string
- instead of an error. (It should be an error as it's a
- decreasing range.) Currently this bug is emulated for backward
- compatibility, but you shouldn't utilize it, as in the future
- it will be certainly an error.</p>
- </li>
- </ul>
-
- <p>Example:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-template"><#assign s = "ABCDEF">
-${s[2..3]}
-${s[2..<4]}
-${s[2..*3]}
-${s[2..*100]}
-${s[2..]}</pre></div>
-
- <p>will print:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-output">CD
-CD
-CDE
-CDEF
-CDEF</pre></div>
-
- <div class="callout note">
- <strong class="callout-label">Note:</strong>
-
- <p>Some of the typical use-cases of string slicing is covered
- by convenient built-ins: <a href="ref_builtins_string.html#ref_builtin_remove_beginning"><code>remove_beginning</code></a>,
- <a href="ref_builtins_string.html#ref_builtin_remove_ending"><code>remove_ending</code></a>,
- <a href="ref_builtins_string.html#ref_builtin_keep_before"><code>keep_before</code></a>,
- <a href="ref_builtins_string.html#ref_builtin_keep_after"><code>keep_after</code></a>,
- <a href="ref_builtins_string.html#ref_builtin_keep_before_last"><code>keep_before_last</code></a>,
- <a href="ref_builtins_string.html#ref_builtin_keep_after_last"><code>keep_after_last</code></a></p>
- </div>
-
-
-
-
-
-
-
-<h2 class="content-header header-section2" id="dgui_template_exp_sequenceop">Sequence operations</h2>
-
-
-
-
-
-
-
-
-
-<h3 class="content-header header-section3" id="dgui_template_exp_sequenceop_cat">Concatenation</h3>
-
-
-
-
-
-
-
-
-
-
- <p>You can concatenate sequences in the same way as strings,
- with <code class="inline-code">+</code>. Example:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-template"><#list ["Joe", "Fred"] + ["Julia", "Kate"] as user>
-- ${user}
-</#list></pre></div>
-
- <p>will print:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-output">- Joe
-- Fred
-- Julia
-- Kate
- </pre></div>
-
- <p>Note that sequence concatenation is not to be used for many
- repeated concatenations, like for appending items to a sequence
- inside a loop. It's just for things like <code class="inline-code"><#list users
- + admins as person></code>. Although concatenating sequences
- is fast and its speed is independently of the size of the
- concatenated sequences, the resulting sequence will be always a
- little bit slower to read than the original two sequences were.
- This way the result of many repeated concatenations is a sequence
- that is slow to read.</p>
-
-
-
-
-
-
-
-<h3 class="content-header header-section3" id="dgui_template_exp_seqenceop_slice">Sequence slicing</h3>
-
-
-
-
-
-
-
-
- <p>With
- <code class="inline-code"><em class="code-color">seq</em>[<em class="code-color">range</em>]</code>,
- were <code class="inline-code"><em class="code-color">range</em></code> is a
- range value <a href="#dgui_template_exp_direct_ranges">as
- described here</a>, you can take a slice of the sequence. The
- resulting sequence will contain the items from the original
- sequence (<code class="inline-code"><em class="code-color">seq</em></code>) whose
- indexes are in the range. For example:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-template"><#assert seq = ["A", "B", "C", "D", "E"]>
-<#list seq[1..3] as i>${i}</#list></pre></div>
-
- <p>will print</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-output">BCD </pre></div>
-
- <p>Furthermore, the items in the slice will be in the same
- order as in the range. Thus for example the above example with the
- <code class="inline-code">3..1</code> range would print
- <code class="inline-code">DCB</code>.</p>
-
- <p>The numbers in the range must be valid indexes in the
- sequence, or else the processing of the template will be aborted
- with error. Like in the last example,
- <code class="inline-code">seq[-1..0]</code> would be an error as
- <code class="inline-code">seq[-1]</code> is invalid, also
- <code class="inline-code">seq[1..5]</code> would be because
- <code class="inline-code">seq[5]</code> is invalid. (Note that
- <code class="inline-code">seq[100..<100]</code> or
- <code class="inline-code">seq[100..*0]</code> would be valid despite that 100 is
- out of bounds, because those ranges are empty.)</p>
-
- <p>Length limited ranges
- (<code class="inline-code"><em class="code-color">start</em>..*<em class="code-color">length</em></code>)
- and right-unbounded ranges
- (<code class="inline-code"><em class="code-color">start</em>..</code>) adapt to
- the length of the sliced sequence. They will slice out at most as
- many items as there is available:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-template"><#assign seq = ["A", "B", "C"]>
-
-Slicing with length limited ranges:
-- <#list seq[0..*2] as i>${i}</#list>
-- <#list seq[1..*2] as i>${i}</#list>
-- <#list seq[2..*2] as i>${i}</#list> <#-- Not an error -->
-- <#list seq[3..*2] as i>${i}</#list> <#-- Not an error -->
-
-Slicing with right-unlimited ranges:
-- <#list seq[0..] as i>${i}</#list>
-- <#list seq[1..] as i>${i}</#list>
-- <#list seq[2..] as i>${i}</#list>
-- <#list seq[3..] as i>${i}</#list></pre></div>
-
- <p>This will print:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-output">Slicing with length limited ranges:
-- AB
-- BC
-- C
--
-
-Slicing with right-unlimited ranges:
-- ABC
-- BC
-- C
--</pre></div>
-
- <p>Note above that slicing with length limited and right
- unbounded ranges allow the starting index to be past the last item
- <em>by one</em> (but no more).</p>
-
- <div class="callout note">
- <strong class="callout-label">Note:</strong>
-
- <p>To split a sequence to slices of a given size, you should
- use the <a href="ref_builtins_sequence.html#ref_builtin_chunk"><code>chunk</code></a>
- built-in.</p>
- </div>
-
-
-
-
-
-
-
-<h2 class="content-header header-section2" id="dgui_template_exp_hashop">Hash operations</h2>
-
-
-
-
-
-
-
-
-
-<h3 class="content-header header-section3" id="dgui_template_exp_hashop_cat">Concatenation</h3>
-
-
-
-
-
-
-
-
-
-
- <p>You can concatenate hashes in the same way as strings, with
- <code class="inline-code">+</code>. If both hashes contain the same key, the
- hash on the right-hand side of the <code class="inline-code">+</code> takes
- precedence. Example:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-template"><#assign ages = {"Joe":23, "Fred":25} + {"Joe":30, "Julia":18}>
-- Joe is ${ages.Joe}
-- Fred is ${ages.Fred}
-- Julia is ${ages.Julia}</pre></div>
-
- <p>will print:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-output">- Joe is 30
-- Fred is 25
-- Julia is 18</pre></div>
-
- <p>Note that hash concatenation is not to be used for many
- repeated concatenations, like for adding items to a hash inside a
- loop. It's the same as with the <a href="#dgui_template_exp_sequenceop_cat">sequence
- concatenation</a>.</p>
-
-
-
-
-
-
-<h2 class="content-header header-section2" id="dgui_template_exp_arit">Arithmetical calculations</h2>
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- <p>This is the basic 4-function calculator arithmetic plus the
- modulus operator. So the operators are:</p>
-
- <ul>
- <li>
- Addition: <code class="inline-code">+</code>
- </li>
-
- <li>
- Subtraction: <code class="inline-code">-</code>
- </li>
-
- <li>
- Multiplication: <code class="inline-code">*</code>
- </li>
-
- <li>
- Division: <code class="inline-code">/</code>
- </li>
-
- <li>
- Modulus (remainder) of integer operands:
- <code class="inline-code">%</code>
- </li>
- </ul>
-
-
-
- <p>Example:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-template">${100 - x * x}
-${x / 2}
-${12 % 10}</pre></div>
-
- <p>Assuming that <code class="inline-code">x</code> is 5, it will print:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-output">75
-2.5
-2</pre></div>
-
- <p>Both operands must be expressions which evaluate to a
- numerical value. So the example below will cause an error when
- FreeMarker tries to evaluate it, since <code class="inline-code">"5"</code> is a
- string and not the number 5:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-template">${3 * "5"} <#-- WRONG! --></pre></div>
-
- <p>There is an exception to the above rule. The
- <code class="inline-code">+</code> operator, is used to <a href="#dgui_template_exp_stringop_interpolation">concatenate
- strings</a> as well. If on one side of <code class="inline-code">+</code> is a
- string and on the other side of <code class="inline-code">+</code> is a numerical
- value, then it will convert the numerical value to string (using the
- format appropriate for language of the page) and then use the
- <code class="inline-code">+</code> as string concatenation operator.
- Example:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-template">${3 + "5"}</pre></div>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-output">35</pre></div>
-
- <p>Generally, FreeMarker never converts a string to a number
- automatically, but it may convert a number to a string
- automatically.</p>
-
- <p> People often want only the integer part of the result
- of a division (or of other calculations). This is possible with the
- <code class="inline-code">int</code> built-in. (Built-ins are explained <a href="#dgui_template_exp_builtin">later</a>):</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-template">${(x/2)?int}
-${1.1?int}
-${1.999?int}
-${-1.1?int}
-${-1.999?int}</pre></div>
-
- <p>Assuming that <code class="inline-code">x</code> is 5, it will print:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-output">2
-1
-1
--1
--1</pre></div>
-
- <p>Due to historical reasons, the <code class="inline-code">%</code> operator
- works by first truncating the operands to an integer number, and
- then returning the remainder of the division:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-template">${12 % 5} <#-- Prints 2 -->
-${12.9 % 5} <#-- Prints 2 -->
-${12.1 % 5} <#-- Prints 2 -->
-
-${12 % 6} <#-- Prints 0 -->
-${12 % 6.9} <#-- Prints 0 --></pre></div>
-
- <p>The sign of the result of <code class="inline-code">%</code> is the same as
- the sign of the left hand operand, and its absolute value is the
- same as if both operands where positive:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-template">${-12 % -5} <#-- Prints -2 -->
-${-12 % 5} <#-- Prints -2 -->
-${12 % -5} <#-- Prints 2 --></pre></div>
-
-
-
-
-
-<h2 class="content-header header-section2" id="dgui_template_exp_comparison">Comparison</h2>
-
-
-
-
- <p>Sometimes you want to know if two values are equal or not, or
- which value is the greater.</p>
-
- <p>To show concrete examples I will use the <code class="inline-code">if</code>
- directive here. The usage of <code class="inline-code">if</code> directive is:
- <code class="inline-code"><#if
- <em class="code-color">expression</em>>...</#if></code>,
- where expression must evaluate to a boolean value or else an error
- will abort the processing of the template. If the value of
- expression is <code class="inline-code">true</code> then the things between the
- begin and end-tag will be processed, otherwise they will be
- skipped.</p>
-
- <p>To test two values for equality you use <code class="inline-code">==</code>
- (or <code class="inline-code">=</code> as a <em>deprecated</em>
- alternative) To test two values for inequality you use
- <code class="inline-code">!=</code>. For example, assume that
- <code class="inline-code">user</code> is "Big Joe":</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-template"><#if <strong>user == "Big Joe"</strong>>
- It is Big Joe
-</#if>
-<#if <strong>user != "Big Joe"</strong>>
- It is not Big Joe
-</#if></pre></div>
-
- <p>The <code class="inline-code">user == "Big Joe"</code> expression in the
- <code class="inline-code"><#if ...></code> will evaluate to the boolean
- <code class="inline-code">true</code>, so the above will say "It is Big
- Joe".</p>
-
- <p>The expressions on both sides of the <code class="inline-code">==</code> or
- <code class="inline-code">!=</code> must evaluate to a scalar (not a sequence or
- hash). Furthermore, the two scalars must have the same type (i.e.
- strings can only be compared to strings and numbers can only be
- compared to numbers, etc.) or else an error will abort template
- processing. For example <code class="inline-code"><#if 1 == "1"></code> will
- cause an error. Note that FreeMarker does exact comparison, so
- string comparisons are case and white-space sensitive:
- <code class="inline-code">"x"</code> and <code class="inline-code">"x�"</code> and
- <code class="inline-code">"X"</code> are not equal values.</p>
-
- <p>For numerical and date, time and date-time values you can also
- use <code class="inline-code"><</code>, <code class="inline-code"><=</code>,
- <code class="inline-code">>=</code> and <code class="inline-code">></code>. You can't use
- them for strings! Example:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-template"><#if x <strong><=</strong> 12>
- x is less or equivalent with 12
-</#if></pre></div>
-
- <p>There's a problem with <code class="inline-code">>=</code> and
- <code class="inline-code">></code>. FreeMarker interprets the
- <code class="inline-code">></code> character as the closing character of the
- FTL tag. To prevent this, you can use <code class="inline-code">lt</code> instead
- of <code class="inline-code"><</code>, <code class="inline-code">lte</code> instead of
- <code class="inline-code"><=</code>, <code class="inline-code">gt</code> instead of
- <code class="inline-code">></code> and <code class="inline-code">gte</code> instead of
- <code class="inline-code">>=</code>, like in <code class="inline-code"><#if x gt
- y></code>. Another trick it to put the expression into <a href="#dgui_template_exp_parentheses">parentheses</a> like in
- <code class="inline-code"><#if (x > y)></code>, although it's considered
- to be less elegant.</p>
-
- <div class="callout note">
- <strong class="callout-label">Note:</strong>
-
- <p>FreeMarker supports some other alternatives too, but these
- are deprecated:</p>
-
- <ul>
- <li>
- <p>Writing <code class="inline-code">&gt;</code> and
- <code class="inline-code">&lt;</code> on the place of the problematic
- relation marks, like in: <code class="inline-code"><#if x &gt;
- y></code> or <code class="inline-code"><#if x &gt;=
- y></code> . Note that in general FTL does not support
- entity references (the
- <code class="inline-code">&<em class="code-color">...</em>;</code>
- things) in FTL tags; it's just an exception with the
- arithmetical comparisons.</p>
- </li>
-
- <li>
- <p><code class="inline-code">\lt</code>, <code class="inline-code">\lte</code>,
- <code class="inline-code">\gt</code> and <code class="inline-code">\gte</code> which are
- the same as the ones without the backslash</p>
- </li>
- </ul>
- </div>
-
-
-
-
-
-
-<h2 class="content-header header-section2" id="dgui_template_exp_logicalop">Logical operations</h2>
-
-
-
-
-
-
-
-
-
-
-
-
- <p>Just the usual logical operators:</p>
-
- <ul>
- <li>
- Logical or: <code class="inline-code">||</code>
- </li>
-
- <li>
- Logical and: <code class="inline-code">&&</code>
- </li>
-
- <li>
- Logical not: <code class="inline-code">!</code>
- </li>
- </ul>
-
- <p>The operators will work with boolean values only. Otherwise an
- error will abort the template processing.</p>
-
- <p>Example:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-template"><#if x < 12 <strong>&&</strong> color == "green">
- We have less than 12 things, and they are green.
-</#if>
-<#if <strong>!</strong>hot> <#-- here hot must be a boolean -->
- It's not hot.
-</#if></pre></div>
-
-
-
-
-
-<h2 class="content-header header-section2" id="dgui_template_exp_builtin">Built-ins</h2>
-
-
-
-
- <p>Built-ins are like methods that are added to the objects by
- FreeMarker. To prevent name clashes with actual methods and other
- sub-variables, instead of dot (<code class="inline-code">.</code>), you separate
- them from the parent object with question mark
- (<code class="inline-code">?</code>). For example, if you want to ensure that
- <code class="inline-code">path</code> has an initial <code class="inline-code">/</code> then you
- could write <code class="inline-code">path?ensure_starts_with('/')</code>. The
- Java object behind <code class="inline-code">path</code> (a
- <code class="inline-code">String</code> most certainly) doesn't have such method,
- FreeMarker adds it. For brevity, if the method has no parameters,
- you <em>must</em> omit the <code class="inline-code">()</code>, like,
- to get the length of <code class="inline-code">path</code>, you have to write
- <code class="inline-code">path?length</code>, <em>not</em>
- <code class="inline-code">path?length()</code>.</p>
-
- <p>The other reason why built-ins are crucial is that normally
- (though it depends on configuration settings), FreeMarker doesn't
- expose the Java API of the objects. So despite that Java's
- <code class="inline-code">String</code> has a <code class="inline-code">length()</code> method,
- it's hidden from the template, you <em>have to</em> use
- <code class="inline-code">path?length</code> instead. The advantage of that is
- that thus the template doesn't depend on the exactly type of the
- underlying Java objects. (Like <code class="inline-code">path</code> is maybe a
- <code class="inline-code">java.nio.Path</code> behind the scenes, but if the
- programmers has configure FreeMarker to expose
- <code class="inline-code">Path</code> objects as FTL strings, the template won't
- be aware of that, and <code class="inline-code">?length</code> will work, despite
- that <code class="inline-code">java.nio.Path</code> has no similar method.)</p>
-
- <p>You can find some of the <a href="dgui_quickstart_template.html#topic.commonlyUsedBuiltIns">most commonly used built-ins
- mentioned here</a>, and the <a href="ref_builtins.html">complete
- list of built-ins in the Reference</a>. For now, just a few of
- the more important ones:</p>
-
- <p>Example:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-template">${testString?upper_case}
-${testString?html}
-${testString?upper_case?html}
-
-${testSequence?size}
-${testSequence?join(", ")}</pre></div>
-
- <p>Assuming that <code class="inline-code">testString</code> stores the string
- "Tom & Jerry", and testSequnce stores the strings
- "foo", "bar" and "baz", the
- output will be:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-output">TOM & JERRY
-Tom &amp; Jerry
-TOM &amp; JERRY
-
-3
-foo, bar, baz</pre></div>
-
- <p>Note the <code class="inline-code">test?upper_case?html</code> above. Since
- the result of <code class="inline-code">test?upper_case</code> is a string, you
- can apply the <code class="inline-code">html</code> built-in on it.</p>
-
- <p>Naturally, the left side of the built-in can be arbitrary
- expression, not just a variable name:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-template">${testSeqence[1]?cap_first}
-${"horse"?cap_first}
-${(testString + " & Duck")?html}</pre></div>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-output">Bar
-Horse
-Tom &amp; Jerry &amp; Duck</pre></div>
-
-
-
-
-
-<h2 class="content-header header-section2" id="dgui_template_exp_methodcall">Method call</h2>
-
-
-
-
-
-
- <p>If you have a method then you can use the method call
- operation on it. The method call operation is a comma-separated list
- of expressions in parentheses. These values are called parameters.
- The method call operation passes these values to the method which
- will in turn return a result. This result will be the value of the
- whole method call expression.</p>
-
- <p>For example, assume the programmers have made available a
- method variable called <code class="inline-code">repeat</code>. You give a string
- as the first parameter, and a number as the second parameter, and it
- returns a string which repeats the first parameter the number of
- times specified by the second parameter.</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-template">${repeat("Foo", 3)}</pre></div>
-
- <p>will print:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-output">FooFooFoo</pre></div>
-
- <p>Here <code class="inline-code">repeat</code> was evaluated to the method
- variable (according to how you <a href="#dgui_template_exp_var_toplevel">access top-level
- variables</a>) and then <code class="inline-code">("What", 3)</code> invoked
- that method.</p>
-
- <p>I would like to emphasize that method calls are just plain
- expressions, like everything else. So this:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-template">${repeat(repeat("x", 2), 3) + repeat("Foo", 4)?upper_case}</pre></div>
-
- <p>will print this:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-output">xxxxxxFOOFOOFOOFOO</pre></div>
-
-
-
-
-
-<h2 class="content-header header-section2" id="dgui_template_exp_missing">Handling missing values</h2>
-
-
- <div class="callout note">
- <strong class="callout-label">Note:</strong>
-
- <p>These operators exist since FreeMarker 2.3.7 (replacing the
- <code class="inline-code">default</code>, <code class="inline-code">exists</code> and
- <code class="inline-code">if_exists</code> built-ins).</p>
- </div>
-
-
-
-
-
-
-
-
-
-
-
-
- <p>As we explained earlier, an error will occur and abort the
- template processing if you try to access a missing variable. However
- two special operators can suppress this error, and handle the
- problematic situation. The handled variable can be top-level
- variable, hash subvariable, or sequence subvariable as well.
- Furthermore these operators handle the situation when a method call
- doesn't return a value <span class="marked-for-programmers">(from the
- viewpoint of Java programmers: it returns <code class="inline-code">null</code> or
- it's return type is <code class="inline-code">void</code>)</span>, so it's more
- correct to say that these operators handle missing values in
- general, rather than just missing variables.</p>
-
- <p><span class="marked-for-programmers">For those who know what's Java
- <code class="inline-code">null</code>, FreeMarker 2.3.<em>x</em>
- treats them as missing values. Simply, the template language doesn't
- know the concept of <code class="inline-code">null</code>. For example, if you
- have a bean that has a <code class="inline-code">maidenName</code> property, and
- the value of that property is <code class="inline-code">null</code>, then that's
- the same as if there were no such property at all, as far as the
- template is concerned (assuming you didn't configured FreeMarker to
- use some extreme object wrapper, that is). The result of a method
- call that returns <code class="inline-code">null</code> is also treated as a
- missing variable (again, assuming that you use some usual object
- wrapper). See more <a href="app_faq.html#faq_null">in the
- FAQ</a>.</span></p>
-
- <div class="callout note">
- <strong class="callout-label">Note:</strong>
-
- <p>If you wonder why is FreeMarker so picky about missing
- variables, <a href="app_faq.html#faq_picky_about_missing_vars">read this
- FAQ entry</a>.</p>
- </div>
-
-
-
-
-
-
-
-<h3 class="content-header header-section3" id="dgui_template_exp_missing_default">Default value operator</h3>
-
-
-
-
- <p>Synopsis:
- <code class="inline-code"><em class="code-color">unsafe_expr</em>!<em class="code-color">default_expr</em></code>
- or <code class="inline-code"><em class="code-color">unsafe_expr</em>!</code> or
- <code class="inline-code">(<em class="code-color">unsafe_expr</em>)!<em class="code-color">default_expr</em></code>
- or
- <code class="inline-code">(<em class="code-color">unsafe_expr</em>)!</code></p>
-
- <p>This operator allows you to specify a default value for the
- case when the value is missing.</p>
-
- <p>Example. Assume no variable called <code class="inline-code">mouse</code>
- is present:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-template">${mouse!"No mouse."}
-<#assign mouse="Jerry">
-${mouse!"No mouse."}</pre></div>
-
- <p>The output will be:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-output">No mouse.
-Jerry</pre></div>
-
- <p>The default value can be any kind of expression, so it
- doesn't have to be a string. For example you can write
- <code class="inline-code">hits!0</code> or <code class="inline-code">colors!["red", "green",
- "blue"]</code>. There is no restriction regarding the
- complexity of the expression that specifies the default value, for
- example you can write: <code class="inline-code">cargo.weight!(item.weight *
- itemCount + 10)</code>.</p>
-
- <div class="callout warning">
- <strong class="callout-label">Warning!</strong>
-
- <p>If you have a composite expression after the
- <code class="inline-code">!</code>, like <code class="inline-code">1 + x</code>,
- <em>always</em> use parenthesses, like
- <code class="inline-code">${x!(1 + y)}</code> or <code class="inline-code">${(x!1) +
- y)}</code>, depending on which interpretation you meant.
- That's needed because due to a programming mistake in FreeMarker
- 2.3.x, the precedence of <code class="inline-code">!</code> (when it's used as
- default value operator) is very low at its right side. This
- means that, for example, <code class="inline-code">${x!1 + y}</code> is
- misinterpreted by FreeMarker as <code class="inline-code">${x!(1 + y)}</code>
- while it should mean <code class="inline-code">${(x!1) + y}</code>. This
- programming error will be fixed in FreeMarker 2.4, so you should
- not utilize this wrong behavior, or else your templates will
- break with FreeMarker 2.4!</p>
- </div>
-
-
- <p>If the default value is omitted, then it will be empty
- string and empty sequence and empty hash at the same time. (This
- is possible because FreeMarker allows multi-type values.) Note the
- consequence that you can't omit the default value if you want it
- to be <code class="inline-code">0</code> or <code class="inline-code">false</code>.
- Example:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-template">(${mouse!})
-<#assign mouse = "Jerry">
-(${mouse!})</pre></div>
-
- <p>The output will be:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-output">()
-(Jerry)</pre></div>
-
- <div class="callout warning">
- <strong class="callout-label">Warning!</strong>
-
- <p>Due to syntactical ambiguities <code class="inline-code"><@something
- a=x! b=y /></code> will be interpreted as
- <code class="inline-code"><@something a=x!(b=y) /></code>, that is, the
- <code class="inline-code">b=y</code> will be interpreted as a comparison that
- gives the default value for <code class="inline-code">x</code>, rather than
- the specification of the <code class="inline-code">b</code> parameter. To
- prevent this, write: <code class="inline-code"><@something a=(x!) b=y
- /></code></p>
- </div>
-
-
- <p>You can use this operator in two ways with non-top-level
- variables:</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-template">product.color!"red"</pre></div>
-
- <p>This will handle if <code class="inline-code">color</code> is missing
- inside <code class="inline-code">product</code> (and returns
- <code class="inline-code">"red"</code> if so), but will not handle if
- <code class="inline-code">product</code> is missing. That is, the
- <code class="inline-code">product</code> variable itself must exist, otherwise
- the template processing will die with error.</p>
-
-
-
-<div class="code-wrapper"><pre class="code-block code-template">(product.color)!&
<TRUNCATED>