std::subtract_with_carry_engine

template<
    class UIntType,
    std::size_t w, std::size_t s, std::size_t r
> class subtract_with_carry_engine;

Is a random number engine that uses subtract with carry algorithm.

The state of a subtract_with_carry_engine consists of a sequence \(\small{\{ X_i\}(0 \le i <r)}\){X
i} (0 ≤ i <r), every \(\small{X_i}\)X
i is in interval \(\small{[0, 2^w)}\)[0, 2w
).

Let all subscripts applied to sequence be taken modulo r, c be the carry value which is either 0 or 1. The state transition is performed as follows:

• let \(\small{Y=X_{i-s}-X_{i-r}-c}\)Y=X
  i-s-X
  i-r-c,
• set \(\small{X_i}\)X
  i to \(\small{Y \mod 2^w}\)Y mod 2w
  ,
• set c to 1, if \(\small{Y<0}\)Y<0, to 0 otherwise.

The following typedefs define the random number engine with two commonly used parameter sets:

Template parameters

Member types

Member functions

Non-member functions

Member constants

Example