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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:
Boost License 1.0
Authors:
Walter Bright

Source core/checkedint.d

pure nothrow @nogc @safe int `adds`(int `x`, int `y`, ref bool `overflow`);
pure nothrow @nogc @safe long `adds`(long `x`, long `y`, ref bool `overflow`);
  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 sum
pure nothrow @nogc @safe uint `addu`(uint `x`, uint `y`, ref bool `overflow`);
pure nothrow @nogc @safe ulong `addu`(ulong `x`, ulong `y`, ref bool `overflow`);
  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 sum
pure nothrow @nogc @safe int `subs`(int `x`, int `y`, ref bool `overflow`);
pure nothrow @nogc @safe long `subs`(long `x`, long `y`, ref bool `overflow`);
  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 difference
pure nothrow @nogc @safe uint `subu`(uint `x`, uint `y`, ref bool `overflow`);
pure nothrow @nogc @safe ulong `subu`(ulong `x`, ulong `y`, ref bool `overflow`);
  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 difference
pure nothrow @nogc @safe int `negs`(int `x`, ref bool `overflow`);
pure nothrow @nogc @safe long `negs`(long `x`, ref bool `overflow`);
  Negate an integer.
  Parameters:

  int `x` | operand
  bool `overflow` | set if `x` cannot be negated, is not affected otherwise

  Returns:
  the negation of `x`
pure nothrow @nogc @safe int `muls`(int `x`, int `y`, ref bool `overflow`);
pure nothrow @nogc @safe long `muls`(long `x`, long `y`, ref bool `overflow`);
  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 product
pure nothrow @nogc @safe uint `mulu`(uint `x`, uint `y`, ref bool `overflow`);
pure nothrow @nogc @safe ulong `mulu`(ulong `x`, uint `y`, ref bool `overflow`);
pure nothrow @nogc @safe ulong `mulu`(ulong `x`, ulong `y`, ref bool `overflow`);
  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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