[jira] [Commented] (ARROW-1491) [C++] Add casting implementations from strings to numbers or boolean

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ARROW-1491?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16348890#comment-16348890 ] 

ASF GitHub Bot commented on ARROW-1491:
---------------------------------------

cpcloud commented on a change in pull request #1387: ARROW-1491: [C++] Add casting implementations from strings to numbers or boolean
URL: https://github.com/apache/arrow/pull/1387#discussion_r165417551
 
 

 ##########
 File path: cpp/src/arrow/compute/kernels/cast.cc
 ##########
 @@ -703,6 +706,106 @@ struct CastFunctor<T, DictionaryType,
   }
 };
 
+// ----------------------------------------------------------------------
+// String to Number
+
+template <typename T>
+typename std::enable_if<std::is_arithmetic<T>::value && !std::is_same<T, int8_t>::value &&
+                            !std::is_same<T, uint8_t>::value,
+                        T>::type
+castStringToNumeric(const std::string& s) {
+  return boost::lexical_cast<T>(s);
+}
+
+template <typename T>
+typename std::enable_if<std::is_same<T, int8_t>::value || std::is_same<T, uint8_t>::value,
+                        T>::type
+castStringToNumeric(const std::string& s) {
+  // Convert to int before casting to T
+  // because boost::lexical_cast does not support 8bit int/uint.
+  return boost::numeric_cast<T>(boost::lexical_cast<int>(s));
+}
+
+template <typename O>
+struct CastFunctor<O, StringType,
+                   typename std::enable_if<std::is_base_of<Number, O>::value>::type> {
+  void operator()(FunctionContext* ctx, const CastOptions& options,
+                  const ArrayData& input, ArrayData* output) {
+    using out_type = typename O::c_type;
+    StringArray input_array(input.Copy());
+
+    auto out_data = GetMutableValues<out_type>(output, 1);
+
+    std::function<out_type(const std::string&)> cast_func;
+
+    for (int64_t i = 0; i < input.length; ++i) {
+      if (input_array.IsNull(i)) {
+        out_data++;
+        continue;
+      }
+
+      std::string s = input_array.GetString(i);
+
+      try {
+        *out_data++ = castStringToNumeric<out_type>(s);
+      } catch (...) {
 
 Review comment:
   I'm concerned about propagating the actual error message instead of just saying "Cast from X to Y failed".

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> [C++] Add casting implementations from strings to numbers or boolean
> --------------------------------------------------------------------
>
>                 Key: ARROW-1491
>                 URL: https://issues.apache.org/jira/browse/ARROW-1491
>             Project: Apache Arrow
>          Issue Type: New Feature
>          Components: C++
>            Reporter: Wes McKinney
>            Assignee: Licht Takeuchi
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 0.9.0
>
>




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