---
name: "std::tr1::exponential_distribution"
section: "3"
platform: "linux"
package: "libstdc++6-4.2-doc"
version: "4.2.4-6"
release: "Debian 5.0 (Lenny)"
platforms: ["linux"]
url: "https://new.carta.tech/std::tr1::exponential_distribution"
---

# std::tr1::exponential\_distribution(3)

## NAME

std::tr1::exponential\_distribution -

## SYNOPSIS

## Detailed Description

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

The formula for the exponential probability mass function is $ p(x) =  e^{- x} $.

Mean$ ac{1}{} $ Median$ ac{ge$\[0, infty\]$ Standard Deviation$ ac{1}{} $ Distribution Statistics

Definition at line 2113 of file random.

### Public Types

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

### Public Member Functions

**exponential\_distribution** (const result\_type &\_\_lambda=result\_type(1))\
 \_RealType **lambda** () const \
 template\<class \_UniformRandomNumberGenerator\> result\_type **operator()** (\_UniformRandomNumberGenerator &\_\_urng)\
 void **reset** ()\

### Friends

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

## Constructor & Destructor Documentation

### template\<typename \_RealType = double\> std::tr1::exponential\_distribution\< \_RealType \>::exponential\_distribution (const result\_type & \_\_lambda = `result_type(1)`)` [inline, explicit]`

Constructs an exponential distribution with inverse scale parameter $  $.

Definition at line 2126 of file random.

## Member Function Documentation

### template\<typename \_RealType = double\> \_RealType std::tr1::exponential\_distribution\< \_RealType \>::lambda () const` [inline]`

Gets the inverse scale parameter of the distribution.

Definition at line 2136 of file random.

### template\<typename \_RealType = double\> void std::tr1::exponential\_distribution\< \_RealType \>::reset ()` [inline]`

Resets the distribution.

Has no effect on exponential distributions.

Definition at line 2145 of file 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 exponential\_distribution\< \_RealType1 \> & \_\_x)` [friend]`

Inserts a exponential\_distribution random number distribution `__x` into the output stream `__os`.

**Parameters:**

*\_\_os* An output stream. \
 *\_\_x* A exponential\_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 \_CharT, typename \_Traits\> std::basic\_istream\<\_CharT, \_Traits\>& operator\>\> (std::basic\_istream\< \_CharT, \_Traits \> & \_\_is, exponential\_distribution\< \_RealType \> & \_\_x)` [friend]`

Extracts a exponential\_distribution random number distribution `__x` from the input stream `__is`.

**Parameters:**

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

**Returns:**

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

Definition at line 2179 of file random.

## Author

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