On 2014-03-27 15:33, Meta wrote:
On Thursday, 27 March 2014 at 13:23:27 UTC, monarch_dodra wrote:
"fold" (from what I understood) is what you call "foldl". It was
discussed to not introduce "foldr", as it's just
"fold!(binaryReverseArgs!Fun)(range.retro);".
Rolls right off the tongue. We seriously need a better alias for
binaryReverseArgs.
Is it even necessary to specifically have a binary version of that?
This seems to be a working generalization of binaryReverseArgs:
template reverseArgs(alias pred)
{
import std.typetuple : Reverse;
auto reverseArgs(Args...)(Args args)
if (is(typeof(pred(Reverse!args))))
{
return pred(Reverse!args);
}
}
unittest
{
import std.functional;
alias gt = reverseArgs!(binaryFun!("a < b"));
assert(gt(2, 1) && !gt(1, 1));
int x = 42;
bool xyz(int a, int b) { return a * x < b / x; }
auto foo = &xyz;
foo(4, 5);
alias zyx = reverseArgs!(foo);
assert(zyx(5, 4) == foo(4, 5));
int abc(int a, int b, int c) { return a * b + c; }
alias cba = reverseArgs!abc;
assert(abc(91, 17, 32) == cba(32, 17, 91));
}
On the same note, binaryFun and unaryFun seem to me unnecessary
specializations of a more general 'fun' template. Philippe Sigaud has an
implementation in his dranges called naryFun
(https://github.com/PhilippeSigaud/dranges). That code has apparently
not been touched for at least two years, so YMMV.
--
Simen
