On 05/25/2013 11:57 AM, Namal wrote:

> I have one more question towards using unsigned datatype
>
>    assert(sint(-2_147_483_647) - sint(3) == sint(-2_147_483_648));
>    assert(sint(-2_147_483_647) - sint(3) == sint(2_147_483_648));
>
> Here I get an error for the second line, because it cannot be convertet

It helps a lot if you tell the error message. After making some assumption I was able to produce an error message:

Error: cannot implicitly convert expression (2147483648L) of type long to int

It makes sense if sint is Saturated!int. 2147483648 is long but the struct member is int.

> if i use unsigned
>
>    assert(sint(-2_147_483_647) - sint(3) == sint(-2_147_483_648));
>    assert(sint(-2_147_483_647) - sint(3) == sint(2_147_483_648u));
>
> it makes no difference and I get an error.

This time 2_147_483_648u is a uint which happens to have automatic conversion to int. Automatic type conversions can be extremely confusing. Let's see...

import std.stdio;

struct S
{
    int i;
}

void main()
{
    // uint converts to int:
    auto s = S(1u);

    int i;
    uint u = uint.max;
    // same:
    i = u;

    // Surprising result:
    assert(i == -1);
}

These rules are both because they are same or similar in C and also for convenience. But yes, they can be confusing...

Ali

Is this code available in any repo/archive somewhere?

/Per