Overview of source to source translation strategies

in progress

Goal: text input to text output; usually source code.

Formal systems

ASF+SDF. Symbol differentiator has syntax then separate rewrite rules like:

d(E1+E2)/dV = dE1/dV + dE2/dV
E + 0 = E

Stratego does same but can also do AST rewrites.

TXL rewrites with union grammars

ANTLR

Tree grammars + templates

Rewrite only if result is same AST structure else annotate and build other structures then emit code.

Instruction generators

TWIG, BURG, etc...

Tom Harwood's JBURG example (partial):

/*
 *  Recogize a PLUS node, add up its operands, and return the result.
 */
reg = ExprParser.PLUS(reg arg1, reg arg2): 1
{
    Object dst = regAlloc.allocateRegister(#reg);
    mipsEmitter.printInstruction ( "add", dst, arg1, arg2);
	return dst;
}
/*
 *  Load a constant into a register.
 */
reg = constant : 1
{
    Object dst = regAlloc.allocateRegister(#reg);
	mipsEmitter.printInstruction("li", dst, #reg, null);
	return dst;
}

Tweaking source

Use TokenRewriteStream to insert/replace/delete rather than create tree and then try to regenerate same thing with comments and whitespace.