Janino looks powerful. It compiles expressions, scripts, classes, etc. either from source code or programmatically. But the code samples elicited my moan reflex.
- The "Use Janino as an Expression Evaluator" code snippets look simple enough, but to really try them yourself, you need to: wrap in boilerplate, compile, tweak, execute, scratch head, add System.out.println() statements, remix ... keep that cycle up and you'll know what's going on after a while.
- Or, just run the example classes with their command-line syntax. Simple enough... but we're trying to learn an API here, right? Command-line switches insulate us from the API, which is the opposite of what we want.
Enter
Jython. The same code from the Expression Evaluator code snippets,
remixed here in shot-glass form:
D:\>jython
Jython 2.1 on java1.4.2_06 (JIT: null)
Type "copyright", "credits" or "license" for more information.
>>> from org.codehaus.janino import ExpressionEvaluator
>>> from java.lang import Integer
>>> ee = ExpressionEvaluator("c > d ? c : d", Integer.TYPE, ["c","d"], [Integer.TYPE,Integer.TYPE] )
>>> ee.evaluate( [10,11] )
11
>>>
Nice. I typed as many Janino lines as boilerplate lines. Four lines in, I'm already seeing useful results. That actually makes me want to, I don't know, evaluate another expression:
>>> ee.evaluate( [5,2] )
5
>>>
It's going to be great fun exploring this API. ScriptEvaluator, ClassBodyEvaluator, Compiler, AST ...
Jython users, start your engines.
