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Random Sources ( random_source )

Definition

An instance of type random_source is a random source. It allows to generate uniformly distributed random bits, characters, integers, and doubles. It can be in either of two modes: In bit mode it generates a random bit string of some given length p ( 1 < = p < = 31) and in integer mode it generates a random integer in some given range [low..high] ( low < = high < low + 231). The mode can be changed any time, either globally or for a single operation. The output of the random source can be converted to a number of formats (using standard conversions).

#include < LEDA/core/random_source.h >

Creation

random_source S creates an instance S of type random_source, puts it into bit mode, and sets the precision to 31.

random_source S(int p) creates an instance S of type random_source, puts it into bit mode, and sets the precision to p ( 1 < = p < = 31).

random_source S(int low, int high) creates an instance S of type random_source, puts it into integer mode, and sets the range to [low..high].

Operations

unsigned long S.get() returns a random unsigned integer of maximal precision (32 bits on 32-bit systems and 64 bits on 64-bit systems).

void S.set_seed(int s) resets the seed of the random number generator to s.

int S.reinit_seed() generates and sets a new seed s. The return value is s.

void S.set_range(int low, int high)
    sets the mode to integer mode and changes the range to [low..high].

int S.set_precision(int p) sets the mode to bit mode, changes the precision to p bits and returns previous precision.

int S.get_precision() returns current precision of S.

random_source& S » char& x extracts a character x of default precision or range and returns S, i.e., it first generates an unsigned integer of the desired precision or in the desired range and then converts it to a character (by standard conversion).

random_source& S » unsigned char& x extracts an unsigned character x of default precision or range and returns S.

random_source& S » int& x extracts an integer x of default precision or range and returns S.

random_source& S » long& x extracts a long integer x of default precision or range and returns S.

random_source& S » unsigned int& x extracts an unsigned integer x of default precision or range and returns S.

random_source& S » unsigned long& x extracts a long unsigned integer x of default precision or range and returns S.

random_source& S » double& x extracts a double precision floating point number x in [0, 1], i.e, u/(231 - 1) where u is a random integer in [0..231 - 1], and returns S.

random_source& S » float& x extracts a single precision floating point number x in [0, 1], i.e, u/(231 - 1) where u is a random integer in [0..231 - 1], and returns S.

random_source& S » bool& b extracts a random boolean value (true or false).

int S() returns an integer of default precision or range.

int S(int prec) returns an integer of supplied precision prec.

int S(int low, int high) returns an integer from the supplied range [low..high].


next up previous contents index
Next: Random Variates ( random_variate Up: Simple Data Types and Previous: String Output Streams (   Contents   Index
root 2008-01-09