On Friday, 21 June 2019 at 15:42:56 UTC, Emmanuelle wrote:
Yeah, I want to be able to basically use mixin templates but
with expressions instead, with the code being executed on the
scope of the caller, not the callee; but it seems that's
impossible without passing strings
This sounds very similar to something I hacked together a while
ago and recently wrote about making cleaner code:
https://forum.dlang.org/post/ekbyseslunvmudkhl...@forum.dlang.org
The idea here was to do a pass-by-value lambda. Usage:
---
auto bar(T)(T x) @nogc
{
return x(10);
}
auto foo(int x) @nogc
{
auto f = lambda!(x, q{ (int y) { return x + y; } });
return f;
}
void main()
{
import std.stdio;
writeln(foo(15)(10));
}
---
Magic implementation:
---
template lambda(Args...) {
static struct anon {
static foreach(i; 0 .. Args.length - 1)
mixin("typeof(Args[i]) " ~ __traits(identifier, Args[i]) ~
";");
auto opCall(T...)(T t) {
return mixin(Args[$-1])(t);
}
this(T...)(T t) {
this.tupleof = t;
}
}
anon lambda() {
anon a;
// copy the values in
a.tupleof = Args[0 .. $-1];
return a;
}
}
---
You could convert that into a regular delegate too, so it works
with non-template consumers, by generating a non-templated opCall
and taking its address.
