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#### 20.1.0.0.1 C++ Support

This random number generator is implemented by the RNG class, defined in rng.h:
```class RNG : public TclObject {
enum RNGSources { RAW_SEED_SOURCE, PREDEF_SEED_SOURCE, HEURISTIC_SEED_SOURCE };
...
// These are primitive but maybe useful.
inline int uniform_positive_int() {  // range [0, MAXINT]
return (int)(stream_.next());
}
inline double uniform_double() { // range [0.0, 1.0)
return stream_.next_double();
}

inline int uniform(int k)
{ return (uniform_positive_int() % (unsigned)k); }
inline double uniform(double r)
{ return (r * uniform_double());}
inline double uniform(double a, double b)
{ return (a + uniform(b - a)); }
inline double exponential()
{ return (-log(uniform_double())); }
inline double exponential(double r)
{ return (r * exponential());}
inline double pareto(double scale, double shape)
{ return (scale * (1.0/pow(uniform_double(), 1.0/shape)));}
...
};
```

The uniform_positive_int method generates random integers in the range [0,231-1]. In particular, Additional member functions provide the following random variate generation:

The Random class (in random.h) is an older interface to the standard random number stream.

Here's a sample use of RNG modeled on RED. rng_ is an instance of class RNG:

```        \ldots
// drop probability is computed, pick random number and act
double u = rng_-\>uniform_double();
if (u \<= edv_.v_prob) {
edv_.count = 0;
if (edp_.setbit)
iph-\>flags() |= IP_ECN; /* ip ecn bit /
else
return (1);
}
\ldots
```

2000-08-24