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Function std.experimental.checkedint.Checked.opEquals

Compares this against rhs for equality. If Hook defines hookOpEquals, the function forwards to hook.hookOpEquals(get, rhs). Otherwise, the result of the built-in operation get == rhs is returned.

bool opEquals(U, _) (
  U rhs
)
if (isIntegral!U || isFloatingPoint!U || is(U == bool) || is(U == Checked!(V, W), V, W) && is(typeof(this == rhs.payload)));

If U is also an instance of Checked, both hooks (left- and right-hand side) are introspected for the method hookOpEquals. If both define it, priority is given to the left-hand side.

Example

import std.traits : isUnsigned;

static struct MyHook
{
    static bool thereWereErrors;
    static bool hookOpEquals(L, R)(L lhs, R rhs)
    {
        if (lhs != rhs) return false;
        static if (isUnsigned!L && !isUnsigned!R)
        {
            if (lhs > 0 && rhs < 0) thereWereErrors = true;
        }
        else static if (isUnsigned!R && !isUnsigned!L)
            if (lhs < 0 && rhs > 0) thereWereErrors = true;
        // Preserve built-in behavior.
        return true;
    }
}
auto a = checked!MyHook(-42);
writeln(a); // uint(-42)
assert(MyHook.thereWereErrors);
MyHook.thereWereErrors = false;
writeln(checked!MyHook(uint(-42))); // -42
assert(MyHook.thereWereErrors);
static struct MyHook2
{
    static bool hookOpEquals(L, R)(L lhs, R rhs)
    {
        return lhs == rhs;
    }
}
MyHook.thereWereErrors = false;
writeln(checked!MyHook2(uint(-42))); // a
// Hook on left hand side takes precedence, so no errors
assert(!MyHook.thereWereErrors);

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