Hi
I'm trying to overload the "+" and "-" operators for a struct  but I get
this error

test.d(47): Error: incompatible types for ((v1) - (v2)): 'Vecf!(1u)' and
'Vecf!(1u)'
(the line corresponds to the last assert)

doing something like this

struct Vecf(uint n)
{
    ...
    Vecf!n opBinary(string op)(Vecf!n other) if (op == "+" || op == "-")
{...}
}

void main()
{
    Vecf!1u v1 = Vecf!1u(3f);
    Vecf!1u v2 = Vecf!1u(5f);
    Vecf!1u r = Vecf!1u(-2f);
    assert ((v1.opBinary!"-"(v2)) == r);
    assert ((v1 - v2) == r);
}

removing the last assert or replacing (Vecf!n other) by (Vecf!1u other) in
the function declaration works fine, but it's not what I want

Any ideas? maybe I'm overloading the operators in the wrong way (it worked in a very similar test though)?

Thanks!!

Here's the full code:

-------------------------------------------------------------------
module test;

import std.stdio;

struct Vecf(uint n)
{
    float[n] data;


    this(float[n] args ...)
    {
        foreach (i, a; args)
        {
            data[i] = a;
        }
    }

    float opIndex(uint i)
    {
        return data[i];
    }

    float opIndexAssign(float value, uint i)
    {
        data[i] = value;
        return value;
    }

    Vecf!n opBinary(string op)(Vecf!n other) if (op == "+" || op == "-")
    {
        Vecf!n ret;

        for (size_t i = 0; i < n; i++)
        {
            mixin("ret[i] = this[i] " ~ op ~ " other[i];");
        }
        return ret;
    }
}

void main()
{
    Vecf!1u v1 = Vecf!1u(3f);
    Vecf!1u v2 = Vecf!1u(5f);
    Vecf!1u r = Vecf!1u(-2f);
    assert ((v1.opBinary!"-"(v2)) == r);
    assert ((v1 - v2) == r);
}
--------------------------------------------------------------------------------------

Diego Canuhé:

> I'm trying to overload the "+" and "-" operators for a struct  but I get this error
> 
> test.d(47): Error: incompatible types for ((v1) - (v2)): 'Vecf!(1u)' and
> 'Vecf!(1u)'
> (the line corresponds to the last assert)

It's a dmd bug, and I think it's already in Bugzilla. This is workaround code:


struct Vecf(uint n) {
    float x;
    Vecf opBinary(string op)(Vecf other) if (op == "+" || op == "-") {
        mixin("return Vecf(this.x " ~ op ~ " other.x);");
    }
}

void main() {
    alias Vecf!1 V;
    auto v1 = V(3f);
    auto v2 = V(5f);
    auto r = V(-2f);
    assert ((v1.opBinary!"-"(v2)) == r); // better to use an approximate ==
    assert ((v1 - v2) == r); // better to use an approximate ==
}

Bye,
bearophile

thanks!

On Tue, Jul 26, 2011 at 9:12 AM, bearophile <bearophileHUGS@lycos.com>wrote:

> Diego Canuhé:
>
> > I'm trying to overload the "+" and "-" operators for a struct  but I get this error
> >
> > test.d(47): Error: incompatible types for ((v1) - (v2)): 'Vecf!(1u)' and
> > 'Vecf!(1u)'
> > (the line corresponds to the last assert)
>
> It's a dmd bug, and I think it's already in Bugzilla. This is workaround code:
>
>
> struct Vecf(uint n) {
>    float x;
>    Vecf opBinary(string op)(Vecf other) if (op == "+" || op == "-") {
>        mixin("return Vecf(this.x " ~ op ~ " other.x);");
>    }
> }
>
> void main() {
>    alias Vecf!1 V;
>    auto v1 = V(3f);
>    auto v2 = V(5f);
>    auto r = V(-2f);
>    assert ((v1.opBinary!"-"(v2)) == r); // better to use an approximate ==
>    assert ((v1 - v2) == r); // better to use an approximate ==
> }
>
> Bye,
> bearophile
>