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Module 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

Functions

Name Description
adds Add two signed integers, checking for overflow.
addu Add two unsigned integers, checking for overflow (aka carry).
muls Multiply two signed integers, checking for overflow.
mulu Multiply two unsigned integers, checking for overflow (aka carry).
negs Negate an integer.
subs Subtract two signed integers, checking for overflow.
subu Subtract two unsigned integers, checking for overflow (aka borrow).

Authors

Walter Bright

License

Boost License 1.0

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