Re: Unexpected behaviour in associative array

[Arredondo via Digitalmars-d-learn]

On Friday, 19 April 2019 at 11:32:17 UTC, Andre Pany wrote:
Could you please post the coding, otherwise it is quite hard to 
help you.


Here's a reasonably-sized code fragment that demonstrates the 
issue. I hope the comments along the way are descriptive enough

Thanks,
Arredondo
----------

// this is a thin wrapper around a 2D byte matrix
// that uses an ndslice internally
struct State {
    import std.digest.murmurhash;
        import mir.ndslice;

    this(byte rows, byte cols) inout @safe pure nothrow {
        payload = slice!byte([rows, cols], 0);
    }

    size_t toHash() pure nothrow {
        byte[] data = payload.field();
        immutable digest = digest!(MurmurHash3!(128, 64))(data);
        immutable hash = *cast(size_t*) &digest[0];
        return hash;
    }

    bool opEquals(ref inout State q) inout @safe pure nothrow {
        return payload == q;
    }

    Slice!(Contiguous, [2], byte*) payload;
    alias payload this;
}

void main(string[] args) {
        import std.stdio;

        // create a key
        auto key1 = State(2, 2);
        key1[0, 0] = cast(byte) 1;

        // insert it in an assoc. array
        int[State] map;
        map[key1] = 101;

        // create the exact same key
        auto key2 = State(2, 2);
        key2[0, 0] = cast(byte) 1;

        // it is an identical key as far as the aa is concerned
        assert(key1.opEquals(key2));
        assert(key2.opEquals(key1));
        assert(key1.toHash == key2.toHash);

        // yet it is not in the map
        writeln(key1 in map); // prints some memory address
        writeln(key2 in map); // prints null <-- unexpected behaviour!!!!
}