Getting lazy

Recently, in v250 of the muSE core library, I added support for stack optimization of tail calls - finally!

muSE has been missing the ability to do tail recursion for ever and now its finally there. The absence of tail recursion support had a rather ugly but practical consequence for the language - the while and for looping constructs had a reason to exist because you couldn't loop otherwise without blowing the stack top. I'm glad to note that they can now be safely RIP-d.

Tail call optimization as implemented does not apply to tail calls of native functions. It only applies to applications of user defined functions that appear in the tail position in a block.

As a by-product of the tail call optimization, I was surprised to find it easy to implement lazy evaluation. There's an experimental primitive lcons which can be used to construct a list lazily. This operator is inspired by Dan Friedman's TR44: CONS should not evaluate its arguments technical report. Some classic examples can be found in examples/lcons-v238.scm in the source tree.