C++

Reference

<random>

uniform_real_distribution

class template
<random>

std::uniform_real_distribution

template <class RealType = double> class uniform_real_distribution;
Uniform real distribution
Random number distribution that produces floating-point values according to a uniform distribution, which is described by the following probability density function:



This distribution (also know as rectangular distribution) produces random numbers in a range [a,b) where all intervals of the same length within it are equally probable.

The distribution parameters, a and b, are set on construction.

To produce a random value following this distribution, call its member function operator().

Template parameters

RealType
A floating-point type. Aliased as member type result_type.
By default, this is double.

Member types

The following aliases are member types of uniform_real_distribution:

member typedefinitionnotes
result_typeThe first template parameter (RealType)The type of the numbers generated (defaults to double)
param_typenot specifiedThe type returned by member param.

Member functions

(constructor)
Construct uniform real distribution (public member function)
operator()
Generate random number (public member function)
reset
Reset distribution (public member function)
param
Distribution parameters (public member function)
min
Minimum value (public member function)
max
Upper bound of range (public member function)

Distribution parameters:

a
Lower bound of range (public member function)
b
Upper bound of range (public member function)

Non-member functions

operator<<
Insert into output stream (function template)
operator>>
Extract from input stream (function template)
relational operators
Relational operators (function template)

Example

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// uniform_real_distribution
#include <iostream>
#include <random>

int main()
{
  const int nrolls=10000;  // number of experiments
  const int nstars=95;     // maximum number of stars to distribute
  const int nintervals=10; // number of intervals

  std::default_random_engine generator;
  std::uniform_real_distribution<double> distribution(0.0,1.0);

  int p[nintervals]={};

  for (int i=0; i<nrolls; ++i) {
    double number = distribution(generator);
    ++p[int(nintervals*number)];
  }

  std::cout << "uniform_real_distribution (0.0,1.0):" << std::endl;
  std::cout << std::fixed; std::cout.precision(1);

  for (int i=0; i<nintervals; ++i) {
    std::cout << float(i)/nintervals << "-" << float(i+1)/nintervals << ": ";
    std::cout << std::string(p[i]*nstars/nrolls,'*') << std::endl;
  }

  return 0;
}

Possible output:
uniform_real_distribution (0.0,1.0):
0.0-0.1: *********
0.1-0.2: *********
0.2-0.3: *********
0.3-0.4: *********
0.4-0.5: *********
0.5-0.6: *********
0.6-0.7: *********
0.7-0.8: *********
0.8-0.9: *********
0.9-1.0: *********


See also

uniform_int_distribution
Uniform discrete distribution (class template)
generate_canonical
Generate canonical numbers (function template)