On 03.04.2017 23:43, Meta wrote:
On Monday, 3 April 2017 at 21:33:20 UTC, Timon Gehr wrote:
On 03.04.2017 20:24, Meta wrote:
On Monday, 3 April 2017 at 08:53:57 UTC, Andrea Fontana wrote:
https://isocpp.org/files/papers/p0636r0.html
The fold expressions and inference of constructor template args look
very nice. C++ is quickly catching up to D in a lot of areas, although
usually still with worse syntax. I don't know how fold expressions could
be emulated in D.
String mixins.
I try to avoid string mixins if possible as they're incredibly ugly. I
did try hacking something together with templates and string mixins,
though, but could not get it to work. I stopped here:
template fold(string op, Args...)
{
static if (Args.length == 1)
enum fold = Args[0];
else
enum fold = mixin("Args[0] " ~ op ~ " fold!(op, Args[1..$])");
//variable _param_2 cannot be read at compile time
}
auto f(Args...)(Args args)
{
return fold!("+", args);
}
void main()
{
assert(f(1, 2, 3) == 6);
}
Any suggestions as to how to get something similar working?
I usually just use:
mixin(iota(args.length).map!(i=>text("args[",i,"]")).join("+"))
Obvious and fully customizable; IMHO, the aesthetics are actually better
than for the C++ example:
"0 + ... + args" ?
"0 + args" does not make sense, so why should "0 + ... + args" ?
Furthermore, the feature explicitly special-cases operators (why not
allow fold over arbitrary binary functions?) and adds a few more rules
to C++'s language definition.
