Re: Returning multiple arrays from function - struct or byref the only option?

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On Wednesday, 15 October 2014 at 16:48:24 UTC, Laeeth Isharc 
wrote:
Hi.

I have to write a bunch of functions that operate on input 
arrays to return multiple output arrays.

In case helpful the inputs are price bars or economic data 
points (datetime, ohlc) and the outputs are nx1 arrays (I won't 
say vectors) of doubles or structs.

What is the best way to return multiple arrays in this kind of 
situation.  In Python I returned a tuple of numpy arrays, and 
the C way would be to pass a pointer to the return 
destinations, and I guess I could do the same in a D way by 
passing by ref not value).

I see that I can return a struct containing dynamic arrays, and 
return it (by value of course).  I have read the forum 
discussion a while back over how to return multiple values, and 
tried using tuples.  I don't see that I can return a tuple of 
arrays - am I missing something?

Here is a simple case.  Can I do better ?

Thanks.


import std.typecons;
import std.stdio;

struct RetStruct
{
        double[] a;
        double[] b;
}

RetStruct myfunction(double x)
{
        RetStruct s;
        double[] a,b;
        a~=x+1.0;
        a~=x+9.0;
        b~=x+2.0;
        b~=x+11.0;
        s.a=a;
        s.b=b;
        return s;
}

void main()
{
        writefln("%s",myfunction(99.0));
}

You could also return an std.typecons.Tuple containing both 
arrays. http://dlang.org/phobos/std_typecons.html#.Tuple