Re: opCmp on a struct keyed by an array of bytes

[Ali Çehreli]

On 11/12/2013 01:06 PM, Charles Hixson wrote:

Is there any better way to write the method than:
(cmp doesn't seem to work, and byte arrays don't have an opCmp method.)

  int opCmp(ref const B24 b) const
{    for    (int i = 0;    i < 24;    i++)
       {    if    (bytes[i] < b.bytes[i])    return    -1;
             if    (bytes[i] > b.bytes[i])    return    1;
        }
        return    0;
}    //    opCmp

FWIW, the key is a fixed length array of ubyte, but similar structs have
differing lengths.   If it's not supported by the system I don't want to
do something like casting the pieces
to ulongs and comparing those rather than the bytes.  The added
complexity isn't worth it.

There is std.algorithm.cmp:

import std.algorithm;

struct B24
{
    byte[24] bytes;

    int opCmp(ref const B24 b) const
    {
        return bytes[].cmp(b.bytes[]);
    }
}

void main()
{
    auto a = B24();
    auto b = B24();

    assert(a == b);

    a.bytes[23] = 1;
    assert(a > b);

    b.bytes[22] = 1;
    assert(b > a);
}

Ali