/// losing precision only when necessary.
///
/// If the output value of \c LDigits (\c RDigits) is \c 0, the output value of
-/// \c LScale (\c RScale) is unspecified. If both \c LDigits and \c RDigits
-/// are \c 0, the output value is one of \c LScale and \c RScale; which is
-/// unspecified.
+/// \c LScale (\c RScale) is unspecified.
+///
+/// As a convenience, returns the matching scale. If the output value of one
+/// number is zero, returns the scale of the other. If both are zero, which
+/// scale is returned is unspecifed.
template <class DigitsT>
-void matchScales(DigitsT &LDigits, int16_t &LScale, DigitsT &RDigits,
- int16_t &RScale) {
+int16_t matchScales(DigitsT &LDigits, int16_t &LScale, DigitsT &RDigits,
+ int16_t &RScale) {
static_assert(!std::numeric_limits<DigitsT>::is_signed, "expected unsigned");
- if (LScale < RScale) {
+ if (LScale < RScale)
// Swap arguments.
- matchScales(RDigits, RScale, LDigits, LScale);
- return;
- }
- if (!LDigits || !RDigits || LScale == RScale)
- return;
+ return matchScales(RDigits, RScale, LDigits, LScale);
+ if (!LDigits)
+ return RScale;
+ if (!RDigits || LScale == RScale)
+ return LScale;
// Now LScale > RScale. Get the difference.
int32_t ScaleDiff = int32_t(LScale) - RScale;
if (ScaleDiff >= 2 * getWidth<DigitsT>()) {
// Don't bother shifting. RDigits will get zero-ed out anyway.
RDigits = 0;
- return;
+ return LScale;
}
// Shift LDigits left as much as possible, then shift RDigits right.
if (ShiftR >= getWidth<DigitsT>()) {
// Don't bother shifting. RDigits will get zero-ed out anyway.
RDigits = 0;
- return;
+ return LScale;
}
LDigits <<= ShiftL;
LScale -= ShiftL;
RScale += ShiftR;
assert(LScale == RScale && "scales should match");
+ return LScale;
}
} // end namespace ScaledNumbers