Properly tail recursive functions in VeLa

[dbenn]

Detecting and handling properly tail recursive functions, e.g. to allow loops.

Detection

• final AST in function is a recursive call, or
• final SELECT AST consequent is a recursive call

Detecting tail recursion is easy enough and not pushing VeLa scopes is also easy, but eliminating recursive calls to eval() is harder. Possibilities:

• compiling VeLa would do it;
• continuation passing vs direct style combined with iteration;
• loop that invokes Java code that handled this: do...while(tailCall && !finished); still doesn't help with recursive eval() calls.