---
name: "std::tr1::normal_distribution"
section: "3cxx"
platform: "linux"
package: "libstdc++6-4.4-doc"
version: "4.4.5-8"
release: "Debian 6.0 (Squeeze)"
platforms: ["linux"]
url: "https://new.carta.tech/std::tr1::normal_distribution/3cxx"
---

# std::tr1::normal\_distribution(3cxx)

A normal continuous distribution for random numbers.

## NAME

std::tr1::normal\_distribution -

A normal continuous distribution for random numbers.

## SYNOPSIS

### Public Types

typedef \_RealType **input\_type**\
 typedef \_RealType **result\_type**\

### Public Member Functions

\_RealType **mean** () const \
 **normal\_distribution** (const result\_type &\_\_mean=result\_type(0), const result\_type &\_\_sigma=result\_type(1))\
 template\<class \_UniformRandomNumberGenerator \> result\_type **operator()** (\_UniformRandomNumberGenerator &\_\_urng)\
 void **reset** ()\
 \_RealType **sigma** () const \

### Friends

template\<typename \_RealType1 , typename \_CharT , typename \_Traits \> **std::basic\_ostream**\< \_CharT, \_Traits \> & **operator\<\<** (**std::basic\_ostream**\< \_CharT, \_Traits \> &\_\_os, const **normal\_distribution**\< \_RealType1 \> &\_\_x)\
 template\<typename \_RealType1 , typename \_CharT , typename \_Traits \> **std::basic\_istream**\< \_CharT, \_Traits \> & **operator\>\>** (**std::basic\_istream**\< \_CharT, \_Traits \> &\_\_is, **normal\_distribution**\< \_RealType1 \> &\_\_x)\

## Detailed Description

### template\<typename \_RealType = double\> class std::tr1::normal\_distribution\< \_RealType \>

A normal continuous distribution for random numbers.

The formula for the normal probability mass function is $ p(x) = ac{1}{igma qrt{2 i}} e^{- ac{{x - mean}^ {2}}{2 igma ^ {2}} } $.

Definition at line 2231 of file tr1\_impl/random.

## Constructor & Destructor Documentation

### template\<typename \_RealType = double\> std::tr1::normal\_distribution\< \_RealType \>::normal\_distribution (const result\_type & \_\_mean = `result_type(0)`, const result\_type & \_\_sigma = `result_type(1)`)` [inline, explicit]` Constructs a normal distribution with parameters $ mean $ and $ igma $.

Definition at line 2244 of file tr1\_impl/random.

## Member Function Documentation

### template\<typename \_RealType = double\> \_RealType std::tr1::normal\_distribution\< \_RealType \>::mean () const` [inline]` Gets the mean of the distribution.

Definition at line 2255 of file tr1\_impl/random.

### template\<typename \_RealType \> template\<class \_UniformRandomNumberGenerator \> normal\_distribution\< \_RealType \>::result\_type std::tr1::normal\_distribution\< \_RealType \>::operator() (\_UniformRandomNumberGenerator & \_\_urng) Polar method due to Marsaglia.

Devroye, L. 'Non-Uniform Random Variates Generation.' Springer-Verlag, New York, 1986, Ch. V, Sect. 4.4.

Definition at line 1390 of file random.tcc.

References std::log(), and std::sqrt().

### template\<typename \_RealType = double\> void std::tr1::normal\_distribution\< \_RealType \>::reset ()` [inline]` Resets the distribution.

Definition at line 2269 of file tr1\_impl/random.

### template\<typename \_RealType = double\> \_RealType std::tr1::normal\_distribution\< \_RealType \>::sigma () const` [inline]` Gets the $ igma $ of the distribution.

Definition at line 2262 of file tr1\_impl/random.

## Friends And Related Function Documentation

### template\<typename \_RealType = double\> template\<typename \_RealType1 , typename \_CharT , typename \_Traits \> std::basic\_ostream\<\_CharT, \_Traits\>& operator\<\< (std::basic\_ostream\< \_CharT, \_Traits \> & \_\_os, const normal\_distribution\< \_RealType1 \> & \_\_x)` [friend]` Inserts a normal\_distribution random number distribution `__x` into the output stream `__os`.

**Parameters:**

*\_\_os* An output stream. \
 *\_\_x* A normal\_distribution random number distribution.

**Returns:**

The output stream with the state of `__x` inserted or in an error state.

### template\<typename \_RealType = double\> template\<typename \_RealType1 , typename \_CharT , typename \_Traits \> std::basic\_istream\<\_CharT, \_Traits\>& operator\>\> (std::basic\_istream\< \_CharT, \_Traits \> & \_\_is, normal\_distribution\< \_RealType1 \> & \_\_x)` [friend]` Extracts a normal\_distribution random number distribution `__x` from the input stream `__is`.

**Parameters:**

*\_\_is* An input stream. \
 *\_\_x* A normal\_distribution random number generator engine.

**Returns:**

The input stream with `__x` extracted or in an error state.

## Author

Generated automatically by Doxygen for libstdc++ from the source code.