On Wednesday, 25 February 2015 at 21:25:49 UTC, Daniel N wrote:
Just throwing an idea out there... How about using annotations
to teach the compiler which functions are inverses of
each-other, in order to facilitate optimizing away certain
redundant operations even if they are located inside a
library(i.e. no source).
A little pseudo-code for illustrational purposes, in case my
above text is incomprehensible:
void inc() pure nothrow @inverse(dec)
void dec() pure nothrow @inverse(inc)
void swap(T)(ref T lhs, ref T rhs) pure nothrow @inverse(swap!T)
I like the idea but feel that it's application is too narrow. I
prefer features which are more general and offer greater
flexibility. I believe I've read somewhere that some [functional]
languages define common patterns and equivalent substitutions for
optimization purposes.
inc(dec(x)) -> x
dec(inc(x)) -> x
cos(x)^^2 + sin(x)^^2 -> 1
