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# subtract_with_carry Class

Visual Studio 2008

Generates a random sequence by the subtract with carry algorithm.

```template<class IntType,
IntType M, int S, int R>
class subtract_with_carry {
public:
typedef IntType result_type;
typedef subtract_with_carry<IntType, M, S, R> _Myt;
static const IntType modulus = M;
static const IntType default_seed = 19780503U;
static const int short_lag = S;
static const int long_lag = R;
subtract_with_carry();
explicit subtract_with_carry(unsigned long x0 = default_seed);
template<class Gen>
subtract_with_carry(Gen& gen);
subtract_with_carry(const subtract_with_carry& right);
subtract_with_carry(subtract_with_carry& right);
void seed(unsigned long x0 = 19780503UL);
template<class Gen>
void seed(Gen& gen);
result_type min() const;
result_type max() const;
result_type operator()();
};
```

## Parameters

IntType

The integer result type.

M

The M engine parameter.

S

The S engine parameter.

R

The R engine parameter.

## Remarks

The template class decribes a simple engine that produces values of a user-specified integral type using the recurrence relation x(i) = (x(i - R) - x(i - S) - cy(i - 1)) mod M, where cy(i) has the value 1 if x(i - S) - x(i - R) - cy(i - 1) < 0, otherwise 0. The engine's state is the last R values returned if operator() has been called at least R times, otherwise the M values that have been returned and the last R - M values of the seed.

The template argument IntType must be large enough to hold values up to M - 1. The values of the template arguments S and R must be greater than 0 and S must be less than R.