Usage

`javascript
var randn = require( '@stdlib/random-base-randn' );
`

#### randn()

Returns a standard normally distributed pseudorandom number.

`javascript
var r = randn();
// returns
`

#### randn.factory( \[options] )

Returns a pseudorandom number generator for creating standard normally distributed random numbers.

`javascript
var rand = randn.factory();
`

The function accepts the following options:

- name: name of the underlying pseudorandom number generator which samples from the standard normal distribution.

- [improved-ziggurat][@stdlib/random/base/improved-ziggurat]: improved ziggurat method.
- [box-muller][@stdlib/random/base/box-muller]: Box-Muller transform.

Default: ['improved-ziggurat'][@stdlib/random/base/improved-ziggurat].

- prng: pseudorandom number generator for generating uniformly distributed pseudorandom numbers on the interval [0,1). If provided, the function ignores both the state and seed options. In order to seed the returned pseudorandom number generator, one must seed the provided prng (assuming the provided prng is seedable).

- seed: pseudorandom number generator seed. Valid seed values vary according to the underlying PRNG.

- state: pseudorandom number generator state. Valid state values vary according to the underlying PRNG. If provided, the function ignores the seed option.

- copy: boolean indicating whether to copy a provided pseudorandom number generator state. Setting this option to false allows sharing state between two or more pseudorandom number generators. Setting this option to true ensures that a returned generator has exclusive control over its internal state. Default: true.

By default, the underlying pseudorandom number generator is [improved-ziggurat][@stdlib/random/base/improved-ziggurat]. To use a different PRNG, set the name option.

`javascript
var rand = randn.factory({
'name': 'box-muller'
});

var r = rand();
// returns
`

To use a custom PRNG as the underlying source of uniformly distributed pseudorandom numbers, set the prng option.

`javascript
var minstd = require( '@stdlib/random-base-minstd' );

var rand = randn.factory({
'prng': minstd.normalized
});

var r = rand();
// returns
`

To seed a pseudorandom number generator, set the seed option.

`javascript
var rand1 = randn.factory({
'seed': 12345
});

var r1 = rand1();
// returns

var rand2 = randn.factory({
'seed': 12345
});

var r2 = rand2();
// returns

var bool = ( r1 === r2 );
// returns true
`

To return a generator having a specific initial state, set the generator state option.

`javascript
var rand;
var bool;
var r;
var i;

// Generate pseudorandom numbers, thus progressing the generator state:
for ( i = 0; i < 1000; i++ ) {
r = randn();
}

// Create a new PRNG initialized to the current state of randn:
rand = randn.factory({
'state': randn.state
});

// Test that the generated pseudorandom numbers are the same:
bool = ( rand() === randn() );
// returns true
`

#### randn.NAME

The generator name.

`javascript
var str = randn.NAME;
// returns 'randn'
`

#### randn.PRNG

The underlying pseudorandom number generator.

`javascript
var prng = randn.PRNG;
// returns
`

#### randn.seed

The value used to seed randn().

`javascript
var rand;
var r;
var i;

// Generate pseudorandom values...
for ( i = 0; i < 100; i++ ) {
r = randn();
}

// Generate the same pseudorandom values...
rand = randn.factory({
'seed': randn.seed
});
for ( i = 0; i < 100; i++ ) {
r = rand();
}
`

If provided a PRNG for uniformly distributed numbers, this value is null.

`javascript
var rand = randn.factory({
'prng': Math.random
});

var seed = rand.seed;
// returns null
`

#### randn.seedLength

Length of generator seed.

`javascript
var len = randn.seedLength;
// returns
`

If provided a PRNG for uniformly distributed numbers, this value is null.

`javascript
var rand = randn.factory({
'prng': Math.random
});

var len = rand.seedLength;
// returns null
`

#### randn.state

Writable property for getting and setting the generator state.

`javascript
var r = randn();
// returns

r = randn();
// returns

// ...

// Get a copy of the current state:
var state = randn.state;

r = randn();
// returns

r = randn();
// returns

// Reset the state:
randn.state = state;

// Replay the last two pseudorandom numbers:
r = randn();
// returns

r = randn();
// returns

// ...
`

If provided a PRNG for uniformly distributed numbers, this value is null.

`javascript
var rand = randn.factory({
'prng': Math.random
});

var state = rand.state;
// returns null
`

#### randn.stateLength

Length of generator state.

`javascript
var len = randn.stateLength;
// returns
`

If provided a PRNG for uniformly distributed numbers, this value is null.

`javascript
var rand = randn.factory({
'prng': Math.random
});

var len = rand.stateLength;
// returns null
`

#### randn.byteLength

Size (in bytes) of generator state.

`javascript
var sz = randn.byteLength;
// returns
`

If provided a PRNG for uniformly distributed numbers, this value is null.

`javascript
var rand = randn.factory({
'prng': Math.random
});

var sz = rand.byteLength;
// returns null
`

#### randn.toJSON()

Serializes the pseudorandom number generator as a JSON object.

`javascript
var o = randn.toJSON();
// returns { 'type': 'PRNG', 'name': '...', 'state': {...}, 'params': [] }
`

If provided a PRNG for uniformly distributed numbers, this method returns null.

`javascript
var rand = randn.factory({
'prng': Math.random
});

var o = rand.toJSON();
// returns null
`