Hi there,
I was wondering if std.algorithm.map can take functions with parameters passed by reference? The main point here is to avoid unnecessary copies by perhaps I'm using the wrong tool for the job.

Thank you,
kuba

////////////////////////

import std.algorithm, std.math;
import std.stdio;

double ksqrCpy( double _in){
    return sqrt(_in);
}

void ksqrRef(ref double _in){
    _in = sqrt(_in);
}

void main() {
    double[] arr1 = [ 1, 2, 3, 4 ];
    map!ksqrRef (arr1);
    writeln("a ref : ", arr1);
    auto byCpy= map!ksqrCpy (arr1);
    writeln("a copy: ", byCpy);
}

On Tue, 24 Jun 2014 21:46:15 +0000, kuba wrote:

> Hi there,
> I was wondering if std.algorithm.map can take functions with
> parameters passed by reference? The main point here is to avoid
> unnecessary copies by perhaps I'm using the wrong tool for the
> job.

No, `map` is a _projection_ function and is not intended to perform
modification in place.
There has been discussion of an `each` function which would act as a sink
and which could potentially pass by reference.

On Tuesday, 24 June 2014 at 21:46:16 UTC, kuba wrote:
> The main point here is to avoid unnecessary copies

You should make sure this actually matters - passing doubles by ref for example is probably slower than just passing a regular double.