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core.checkedint
This module implements integral arithmetic primitives that check
for out-of-range results.
Integral arithmetic operators operate on fixed width types.
Results that are not representable in those fixed widths are silently
truncated to fit.
This module offers integral arithmetic primitives that produce the
same results, but set an 'overflow' flag when such truncation occurs.
The setting is sticky, meaning that numerous operations can be cascaded
and then the flag need only be checked at the end.
Whether the operation is signed or unsigned is indicated by an 's' or 'u'
suffix, respectively. While this could be achieved without such suffixes by
using overloading on the signedness of the types, the suffix makes it clear
which is happening without needing to examine the types.
While the generic versions of these functions are computationally expensive
relative to the cost of the operation itself, compiler implementations are free
to recognize them and generate equivalent and faster code.
References Fast Integer Overflow Checks
License:
Authors:
Walter Bright
Source core/checkedint.d
- int
adds
()(intx
, inty
, ref booloverflow
);
longadds
()(longx
, longy
, ref booloverflow
); - Add two signed integers, checking for overflow.The overflow is sticky, meaning a sequence of operations can be done and overflow need only be checked at the end.Parameters:
int x
left operand int y
right operand bool overflow
set if an overflow occurs, is not affected otherwise Returns:the sumExamples:bool overflow; assert(adds(2, 3, overflow) == 5); assert(!overflow); assert(adds(1, int.max - 1, overflow) == int.max); assert(!overflow); assert(adds(int.min + 1, -1, overflow) == int.min); assert(!overflow); assert(adds(int.max, 1, overflow) == int.min); assert(overflow); overflow = false; assert(adds(int.min, -1, overflow) == int.max); assert(overflow); assert(adds(0, 0, overflow) == 0); assert(overflow); // sticky
Examples:bool overflow; assert(adds(2L, 3L, overflow) == 5); assert(!overflow); assert(adds(1L, long.max - 1, overflow) == long.max); assert(!overflow); assert(adds(long.min + 1, -1, overflow) == long.min); assert(!overflow); assert(adds(long.max, 1, overflow) == long.min); assert(overflow); overflow = false; assert(adds(long.min, -1, overflow) == long.max); assert(overflow); assert(adds(0L, 0L, overflow) == 0); assert(overflow); // sticky
- uint
addu
()(uintx
, uinty
, ref booloverflow
);
ulongaddu
()(ulongx
, ulongy
, ref booloverflow
); - Add two unsigned integers, checking for overflow (aka carry).The overflow is sticky, meaning a sequence of operations can be done and overflow need only be checked at the end.Parameters:
uint x
left operand uint y
right operand bool overflow
set if an overflow occurs, is not affected otherwise Returns:the sumExamples:bool overflow; assert(addu(2, 3, overflow) == 5); assert(!overflow); assert(addu(1, uint.max - 1, overflow) == uint.max); assert(!overflow); assert(addu(uint.min, -1, overflow) == uint.max); assert(!overflow); assert(addu(uint.max, 1, overflow) == uint.min); assert(overflow); overflow = false; assert(addu(uint.min + 1, -1, overflow) == uint.min); assert(overflow); assert(addu(0, 0, overflow) == 0); assert(overflow); // sticky
Examples:bool overflow; assert(addu(2L, 3L, overflow) == 5); assert(!overflow); assert(addu(1, ulong.max - 1, overflow) == ulong.max); assert(!overflow); assert(addu(ulong.min, -1L, overflow) == ulong.max); assert(!overflow); assert(addu(ulong.max, 1, overflow) == ulong.min); assert(overflow); overflow = false; assert(addu(ulong.min + 1, -1L, overflow) == ulong.min); assert(overflow); assert(addu(0L, 0L, overflow) == 0); assert(overflow); // sticky
- int
subs
()(intx
, inty
, ref booloverflow
);
longsubs
()(longx
, longy
, ref booloverflow
); - Subtract two signed integers, checking for overflow.The overflow is sticky, meaning a sequence of operations can be done and overflow need only be checked at the end.Parameters:
int x
left operand int y
right operand bool overflow
set if an overflow occurs, is not affected otherwise Returns:the differenceExamples:bool overflow; assert(subs(2, -3, overflow) == 5); assert(!overflow); assert(subs(1, -int.max + 1, overflow) == int.max); assert(!overflow); assert(subs(int.min + 1, 1, overflow) == int.min); assert(!overflow); assert(subs(int.max, -1, overflow) == int.min); assert(overflow); overflow = false; assert(subs(int.min, 1, overflow) == int.max); assert(overflow); assert(subs(0, 0, overflow) == 0); assert(overflow); // sticky
Examples:bool overflow; assert(subs(2L, -3L, overflow) == 5); assert(!overflow); assert(subs(1L, -long.max + 1, overflow) == long.max); assert(!overflow); assert(subs(long.min + 1, 1, overflow) == long.min); assert(!overflow); assert(subs(-1L, long.min, overflow) == long.max); assert(!overflow); assert(subs(long.max, -1, overflow) == long.min); assert(overflow); overflow = false; assert(subs(long.min, 1, overflow) == long.max); assert(overflow); assert(subs(0L, 0L, overflow) == 0); assert(overflow); // sticky
- uint
subu
()(uintx
, uinty
, ref booloverflow
);
ulongsubu
()(ulongx
, ulongy
, ref booloverflow
); - Subtract two unsigned integers, checking for overflow (aka borrow).The overflow is sticky, meaning a sequence of operations can be done and overflow need only be checked at the end.Parameters:
uint x
left operand uint y
right operand bool overflow
set if an overflow occurs, is not affected otherwise Returns:the differenceExamples:bool overflow; assert(subu(3, 2, overflow) == 1); assert(!overflow); assert(subu(uint.max, 1, overflow) == uint.max - 1); assert(!overflow); assert(subu(1, 1, overflow) == uint.min); assert(!overflow); assert(subu(0, 1, overflow) == uint.max); assert(overflow); overflow = false; assert(subu(uint.max - 1, uint.max, overflow) == uint.max); assert(overflow); assert(subu(0, 0, overflow) == 0); assert(overflow); // sticky
Examples:bool overflow; assert(subu(3UL, 2UL, overflow) == 1); assert(!overflow); assert(subu(ulong.max, 1, overflow) == ulong.max - 1); assert(!overflow); assert(subu(1UL, 1UL, overflow) == ulong.min); assert(!overflow); assert(subu(0UL, 1UL, overflow) == ulong.max); assert(overflow); overflow = false; assert(subu(ulong.max - 1, ulong.max, overflow) == ulong.max); assert(overflow); assert(subu(0UL, 0UL, overflow) == 0); assert(overflow); // sticky
- int
negs
()(intx
, ref booloverflow
);
longnegs
()(longx
, ref booloverflow
); - Negate an integer.Parameters:
int x
operand bool overflow
set if x cannot be negated, is not affected otherwise Returns:the negation of xExamples:bool overflow; assert(negs(0, overflow) == -0); assert(!overflow); assert(negs(1234, overflow) == -1234); assert(!overflow); assert(negs(-5678, overflow) == 5678); assert(!overflow); assert(negs(int.min, overflow) == -int.min); assert(overflow); assert(negs(0, overflow) == -0); assert(overflow); // sticky
Examples:bool overflow; assert(negs(0L, overflow) == -0); assert(!overflow); assert(negs(1234L, overflow) == -1234); assert(!overflow); assert(negs(-5678L, overflow) == 5678); assert(!overflow); assert(negs(long.min, overflow) == -long.min); assert(overflow); assert(negs(0L, overflow) == -0); assert(overflow); // sticky
- int
muls
()(intx
, inty
, ref booloverflow
);
longmuls
()(longx
, longy
, ref booloverflow
); - Multiply two signed integers, checking for overflow.The overflow is sticky, meaning a sequence of operations can be done and overflow need only be checked at the end.Parameters:
int x
left operand int y
right operand bool overflow
set if an overflow occurs, is not affected otherwise Returns:the productExamples:bool overflow; assert(muls(2, 3, overflow) == 6); assert(!overflow); assert(muls(-200, 300, overflow) == -60_000); assert(!overflow); assert(muls(1, int.max, overflow) == int.max); assert(!overflow); assert(muls(int.min, 1, overflow) == int.min); assert(!overflow); assert(muls(int.max, 2, overflow) == (int.max * 2)); assert(overflow); overflow = false; assert(muls(int.min, -1, overflow) == int.min); assert(overflow); assert(muls(0, 0, overflow) == 0); assert(overflow); // sticky
Examples:bool overflow; assert(muls(2L, 3L, overflow) == 6); assert(!overflow); assert(muls(-200L, 300L, overflow) == -60_000); assert(!overflow); assert(muls(1, long.max, overflow) == long.max); assert(!overflow); assert(muls(long.min, 1L, overflow) == long.min); assert(!overflow); assert(muls(long.max, 2L, overflow) == (long.max * 2)); assert(overflow); overflow = false; assert(muls(-1L, long.min, overflow) == long.min); assert(overflow); overflow = false; assert(muls(long.min, -1L, overflow) == long.min); assert(overflow); assert(muls(0L, 0L, overflow) == 0); assert(overflow); // sticky
- uint
mulu
()(uintx
, uinty
, ref booloverflow
);
ulongmulu
()(ulongx
, uinty
, ref booloverflow
);
ulongmulu
()(ulongx
, ulongy
, ref booloverflow
); - Multiply two unsigned integers, checking for overflow (aka carry).The overflow is sticky, meaning a sequence of operations can be done and overflow need only be checked at the end.Parameters:
uint x
left operand uint y
right operand bool overflow
set if an overflow occurs, is not affected otherwise Returns:the product
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