[jira] [Commented] (TINKERPOP-1232) Write a tutorial demonstrating the 3 ways to write a Gremlin language variant.

["Marko A. Rodriguez (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/TINKERPOP-1232?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15237240#comment-15237240 ] 

Marko A. Rodriguez commented on TINKERPOP-1232:
-----------------------------------------------

Here is a simple example of how the "String builder"-model would work in a language (model 3). The language would have a class that has the same method API as {{GraphTraversal}}, but it concatenates strings. Look how {{repeat()}} works. Super simple. Thus, the requirement for concatenation and nesting is provided and we can enable Gremlin (without any JVM interactions) in any language.

{code}
public class Test {

  String s;

  public Test(final String source) {
    s = source;
  }

  public Test() {
    s = "";
  }

  public Test V() {
    s = s + ".V()";
    return this;
  }

  public Test outE(final String label) {
    s = s + ".outE(\"${label}\")";
    return this;
  }

  public Test repeat(final Test test) {
    s = s + ".repeat(${test.toString()})";
    return this;
  }

  public String toString() {
    return s;
  }
}
{code}

In action...

{code}
gremlin> g = new Test("g");
==>g
gremlin> g.V().outE("knows")
==>g.V().outE("knows")
gremlin>
gremlin> g = new Test("g");
==>g
gremlin> g.V().repeat(new Test().outE("knows"))
==>g.V().repeat(.outE("knows"))
gremlin>
{code}

Of course, we would create some sort of {{__}}-static class in the host language to replace {{new Test()}} so its pretty. Also, we would have to be smart about {{.}} usage, but this is all simple stuff. The basic idea is there and it "just works." I suppose that hardest part at this point is, submitting the traversal. This is where [~spmallette] comes in. Given a Gremlin-Groovy string traversal, how do I get that to Gremlin Server and get results back?

> Write a tutorial demonstrating the 3 ways to write a Gremlin language variant.
> ------------------------------------------------------------------------------
>
>                 Key: TINKERPOP-1232
>                 URL: https://issues.apache.org/jira/browse/TINKERPOP-1232
>             Project: TinkerPop
>          Issue Type: Improvement
>          Components: documentation
>    Affects Versions: 3.1.1-incubating
>            Reporter: Marko A. Rodriguez
>
> Talking with [~rustyrazorblade] about collaborating on a Gremlin tutorial for language designers. Here is what we came up with.
> We will use Python as the host language and demonstrate 3 ways to create Gremlin-Python.
> * Using Jython: With Jython you have direct access to the JVM and thus can call {{GraphTraversal}} methods directly. We can expose some Python sugar here and there to show why its good to have a language specific variant. See Gremlin-Scala for inspiration.
> * Using JNI: With Python, we have a {{PythonTraversal}} Python class. That class then uses Java Gateway to interact (via proxy) with {{GraphTraversal}}. This was done in the past as an experiment with R using rJava.
> * Using String: With Python, we have a {{PythonTraversal}} Python class where {{out("knows")}} simply appends {{"out(\"knows\")"}} to a string builder. The result can then be a String sent to a {{RemoteConnection}} for evaluation.
> These three models are the three ways in which any language can embed Gremlin. 



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