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@@ -83,3 +83,36 @@ If (big if) this experiment turns out to be useful on some level I'll probably slowly try to make it more self-reliant. My target would be systems programming, possibly even embedded systems, though I don't yet know if this 'paradigm' is powerful enough or if I might need some escape hatches like `unsafe` in Rust. + +### Really, not returns? + +Semantically, yes, although it is useful to convert certain closure calls to +equivalent return statements where possible. This reduces stack usage if nothing +else, and existing compilers are more used to return-oriented programming so it +might also be possible that the produced assembly is more efficient. + +As an example, see `examples/fib.fwd`. The naive C++ currently generated +(besides not actually compiling due to template instantiation depth, heh) +converts what's usually a binary tree of successive calls into a linear sequence +that takes up a huge amount of stack memory. However, we can note that a closure +call is equivalent to a return when + +1. the function has only one closure parameter +2. all code paths end in the closure call +3. the closure call does not reference any local variables by reference + (except references that were taken as parameters) + +Our fibonacci function matches all these cases, and could theoretically be +turned into a more typical return-oriented function for great benefit. Checking +these requirements should be relatively straightforward. + +We could potentially loosen up these requirements, for example we could allow +multiple closure parameters and just return a variant, although the caller now +has to pattern match on the result. Taking things even further, we could start +treating functions more as macros and just replace the function call with the +function body, although this has some other, more fuzzy, requirements like not +allowing recursion. + +We might even want to require that a function can be turned into a 'returning' +function (being pretentious we might prefer calling it 'folding' but anyway) so +that it can be interfaced from C code, for example. |