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Function std.checkedint.Checked.opCmp

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

auto opCmp(U, _) (
  const U rhs
)
if (isIntegral!U || isFloatingPoint!U || is(U == bool));

auto opCmp(U, Hook1, _) (
  Checked!(U,Hook1) rhs
);

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

Parameters

NameDescription
rhs The right-hand side operand
U either the type of rhs or the underlying type if rhs is a Checked instance
Hook1 If rhs is a Checked instance, Hook1 represents the instance's behavior hook

Returns

The result of hookOpCmp if hook defines hookOpCmp. If U is an instance of Checked and hook does not define hookOpCmp, result of rhs.hook.hookOpCmp is returned. If none of the instances specify the behavior via hookOpCmp, -1 is returned if lhs is lesser than rhs, 1 if lhs is greater than rhs and 0 on equality.

Example

import std.traits : isUnsigned;

static struct MyHook
{
    static bool thereWereErrors;
    static int hookOpCmp(L, R)(L lhs, R rhs)
    {
        static if (isUnsigned!L && !isUnsigned!R)
        {
            if (rhs < 0 && rhs >= lhs)
                thereWereErrors = true;
        }
        else static if (isUnsigned!R && !isUnsigned!L)
        {
            if (lhs < 0 && lhs >= rhs)
                thereWereErrors = true;
        }
        // Preserve built-in behavior.
        return lhs < rhs ? -1 : lhs > rhs;
    }
}
auto a = checked!MyHook(-42);
assert(a > uint(42));
assert(MyHook.thereWereErrors);
static struct MyHook2
{
    static int hookOpCmp(L, R)(L lhs, R rhs)
    {
        // Default behavior
        return lhs < rhs ? -1 : lhs > rhs;
    }
}
MyHook.thereWereErrors = false;
assert(Checked!(uint, MyHook2)(uint(-42)) <= a);
//assert(Checked!(uint, MyHook2)(uint(-42)) >= a);
// Hook on left hand side takes precedence, so no errors
assert(!MyHook.thereWereErrors);
assert(a <= Checked!(uint, MyHook2)(uint(-42)));
assert(MyHook.thereWereErrors);

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