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version 2.109.1

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Function core.checkedint.muls

Multiply two signed integers, checking for overflow.

int muls (
  int x,
  int y,
  ref bool overflow
);

long muls (
  long x,
  long y,
  ref bool overflow
);

The overflow is sticky, meaning a sequence of operations can be done and overflow need only be checked at the end.

Parameters

NameDescription
x left operand
y right operand
overflow set if an overflow occurs, is not affected otherwise

Returns

the product

Example

bool overflow;
writeln(muls(2, 3, overflow)); // 6
assert(!overflow);

writeln(muls(-200, 300, overflow)); // -60_000
assert(!overflow);

writeln(muls(1, int.max, overflow)); // int.max
assert(!overflow);

writeln(muls(int.min, 1, overflow)); // int.min
assert(!overflow);

writeln(muls(int.max, 2, overflow)); // (int.max * 2)
assert(overflow);

overflow = false;
writeln(muls(int.min, -1, overflow)); // int.min
assert(overflow);

writeln(muls(0, 0, overflow)); // 0
assert(overflow);                   // sticky

Example

bool overflow;
writeln(muls(2L, 3L, overflow)); // 6
assert(!overflow);

writeln(muls(-200L, 300L, overflow)); // -60_000
assert(!overflow);

writeln(muls(1, long.max, overflow)); // long.max
assert(!overflow);

writeln(muls(long.min, 1L, overflow)); // long.min
assert(!overflow);

writeln(muls(long.max, 2L, overflow)); // (long.max * 2)
assert(overflow);
overflow = false;

writeln(muls(-1L, long.min, overflow)); // long.min
assert(overflow);

overflow = false;
writeln(muls(long.min, -1L, overflow)); // long.min
assert(overflow);

writeln(muls(0L, 0L, overflow)); // 0
assert(overflow);                   // sticky

Authors

Walter Bright

License

Boost License 1.0