stupid

A simple scripting language with a Java runtime and interoperability. Works with Android.

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  • groupId: com.madisp.stupid
  • artifactId: stupid
  • version: 0.1.0

Usage

Imports are omitted for brevity.

Compiling and evaluating an expression (essentially a glorified calculator):

// create a new parser
ExpressionFactory parser = new ExpressionFactory();
// parse a string into an expression tree
Value expr = parser.parseExpression("3 + 5");
// evaluate the expression and print the result
System.out.println(expr.value(new BaseContext())); // prints "8"

Lets spice things up and use a context with some variables instead of the plain BaseContext.

ExpressionFactory parser = new ExpressionFactory();
Value expr = parser.parseExpression("pi*r*r)");
Map<String, Object> vars = new HashMap<String, Object>();
vars.put("pi", Math.PI);
vars.put("r", 2.0f);
// prints "Area of a circle with r=2: 12.566370614359172"
System.out.println("Area of a circle with r=2: " + expr.value(new VarContext(vars)));

Lets also bind it to the System.out object so we can call the println method from the script:

ExpressionFactory parser = new ExpressionFactory();
Value expr = parser.parseExpression("println('Area of a circle with r=2: ' + pi*r*r)");
// a stack context to keep both our vars and binding to System.out
StackContext ctx = new StackContext();
Map<String, Object> vars = new HashMap<String, Object>();
vars.put("pi", Math.PI);
vars.put("r", 2.0f);
ctx.pushExecContext(new VarContext(vars));
// push a reflection context that binds to system.out onto the stack
ctx.pushExecContext(new ReflectionContext(System.out));
// prints "Area of a circle with r=2: 12.566370614359172"
expr.value(ctx);

The Language

Mostly really similar to Java. The grammar lives in src/main/antlr4/Stupid.g4. A short introduction is available in a blogpost.

License

MIT License, see the LICENSE file.