Vector operations doesn't convert to a common type?

[simendsjo]

On 16.04.2011 12:12, simendsjo wrote:
> int[3] a = [1,2,4];
> float[3] b = [1,2,4];
> float[3] c;
> // Why doesn't this work?
> c = a[] + b[]; // Error: incompatible types for ((a[]) + (b[])): 'int[]'
> and 'float[]'
> // When this works?
> c[0] = a[0] + b[0];
> c[1] = a[1] + b[1];
> c[2] = a[2] + b[2];
> assert(c == [2,4,8]);

I tried using a template mixin to avoid having to type this all over, 
but I cannot get it to work.. I think I have something wrong with my 
alias usage, but that's just speculating :)

mixin template ArrayVectorOp(string op, alias dest, alias a, alias b, int I)
if(dest.length == a.length && dest.length == b.length && I >= 1 && I <= 
dest.length) {
     // dest[I-1] = a[I-1] op b[I-1]
     mixin(dest.stringof~"["~(I-1).stringof~"]"
           " = "
           ~a.stringof~"["~(I-1).stringof~"]"
           ~op
           ~b.stringof~"["~(I-1).stringof~"];");

     static if(I > 1)
         mixin ArrayVectorOp!(op, dest, a, b, I-1);
}

void main() {
     int[3]   a = [1,   2,   3];
     float[3] b = [2.1, 3.2, 4.3];
     float[3] c;
     mixin ArrayVectorOp!("+", c, a, b, a.length);
     assert(c == [3.1, 5.2, 7.3]);
}


Gives the following output:

t.d(4): no identifier for declarator c[3 - 1]
t.d(4): Error: c is used as a type
t.d(4): Error: cannot implicitly convert expression (cast(float)a[2u] + 
b[2u]) o
f type float to const(_error_[])
t.d(4): no identifier for declarator c[2 - 1]
t.d(4): Error: c is used as a type
t.d(4): Error: cannot implicitly convert expression (cast(float)a[1u] + 
b[1u]) o
f type float to const(_error_[])
t.d(4): no identifier for declarator c[1 - 1]
t.d(4): Error: c is used as a type
t.d(4): Error: cannot implicitly convert expression (cast(float)a[0u] + 
b[0u]) o
f type float to const(_error_[])
t.d(11): Error: mixin 
t.main.ArrayVectorOp!("+",c,a,b,3u).ArrayVectorOp!(op,c,a,
b,2).ArrayVectorOp!(op,c,a,b,1) error instantiating
t.d(11): Error: mixin 
t.main.ArrayVectorOp!("+",c,a,b,3u).ArrayVectorOp!(op,c,a,
b,2) error instantiating
t.d(18): Error: mixin t.main.ArrayVectorOp!("+",c,a,b,3u) error 
instantiating