On 13.01.2018 01:20, Mark wrote:
Could we also support function tuples?
In principle, yes, though I imagine it is a lot harder to argue for its
inclusion than for that of the features currently proposed in the DIP,
because existing language features already come rather close.
For instance:
int sum(int a, int b) { return a+b; }
int diff(int a, int b) { return a-b; }
(int, int) f = (sum, diff) // no ";" for consistency with existing syntax
No ";" is inconsistent. Also the type of f cannot be (int, int), and
(sum, diff) would try to call sum and diff with 0 arguments and fail.
int (x,y) = f(1, 2); // x=3, y=-1
int (w,z) = (1, 2).f() // same as above, UFCS
int (u,v) = (1, 2).(sum, diff) // same as above, "lambda tuple"
In the last example, (sum, diff) is basically lowered to (x,y) =>
(sum(x,y), diff(x,y)).
I think this is easy enough to achieve without dedicated syntax:
import std.typecons;
template apply(F...){
auto apply(T)(T arg){
import std.conv, std.range, std.algorithm;
return
mixin(text("(",iota(F.length).map!(i=>text("F[",i,"](arg)")).join(","),")"));
}
}
void main(){
int sum(int a, int b) { return a+b; }
int diff(int a, int b) { return a-b; }
auto (u,v)=(1,2).apply!(sum, diff);
import std.stdio;
writeln(u," ",v);
}
