Re: Default constructor for structs

[rouge]

Hi, I'm a newbie, hope the attached example works for you.

Peter Alexander wrote:

Since default constructors for structs are not allowed, how do I go about making all the elements of this Matrix struct default to zero? (floats default to nan by default).

struct Matrix(int M, int N)
{
    float[M][N] elements;
}

Matrix(3, 3) m;
assert(m[0][0] == 0);

?

import std.stdio ;

// directly assign a constant
struct R {
        float[3][3] x = [[0.0F, 0.0F, 0.0F],[0.0F, 0.0F, 0.0F],[0.0F, 0.0F, 
0.0F]] ;
}

// use template
template ZH(int M, T, T value) {
        static if (M == 1)
                const T[M] ZH= [value] ;
        else
                const T[M] ZH= cast(T[M])(ZH!(M - 1, T, value) ~ value)  ;
}

template ZV(alias zh, int N) {
        static if (N == 1)
                const typeof(zh)[N] ZV = [zh];
        else
                const typeof(zh)[N] ZV = cast(typeof(zh)[N])(ZV!(zh, N - 1) ~ 
zh) ;
}

template Zero(int M, int N, T, T value) {
        const float[M][N] Zero = ZV!(ZH!(M, T, value), N);
}

struct S {
        float[4][3] x = Zero!(4,3, float, 0.0F);
}

void main() {
        S s ;
        R r ;
        writefln("%s", s ) ;
        writefln("%s", r ) ;
}

// output : 
//   S([[0 0 0 0] [0 0 0 0] [0 0 0 0]])
//   R([[0 0 0] [0 0 0] [0 0 0]])