Node:Random, Previous:Bitwise Operations, Up:Numbers

#### 21.2.15 Random Number Generation

 copy-random-state [state] Scheme Procedure scm_copy_random_state (state) C Function
 Return a copy of the random state state.

 random n [state] Scheme Procedure scm_random (n, state) C Function
 Return a number in [0, N). Accepts a positive integer or real n and returns a number of the same type between zero (inclusive) and N (exclusive). The values returned have a uniform distribution. The optional argument state must be of the type produced by `seed->random-state`. It defaults to the value of the variable *random-state*. This object is used to maintain the state of the pseudo-random-number generator and is altered as a side effect of the random operation.

 random:exp [state] Scheme Procedure scm_random_exp (state) C Function
 Return an inexact real in an exponential distribution with mean 1. For an exponential distribution with mean u use (* u (random:exp)).

 random:hollow-sphere! v [state] Scheme Procedure scm_random_hollow_sphere_x (v, state) C Function
 Fills vect with inexact real random numbers the sum of whose squares is equal to 1.0. Thinking of vect as coordinates in space of dimension n = (vector-length vect), the coordinates are uniformly distributed over the surface of the unit n-sphere.

 random:normal [state] Scheme Procedure scm_random_normal (state) C Function
 Return an inexact real in a normal distribution. The distribution used has mean 0 and standard deviation 1. For a normal distribution with mean m and standard deviation d use `(+ m (* d (random:normal)))`.

 random:normal-vector! v [state] Scheme Procedure scm_random_normal_vector_x (v, state) C Function
 Fills vect with inexact real random numbers that are independent and standard normally distributed (i.e., with mean 0 and variance 1).

 random:solid-sphere! v [state] Scheme Procedure scm_random_solid_sphere_x (v, state) C Function
 Fills vect with inexact real random numbers the sum of whose squares is less than 1.0. Thinking of vect as coordinates in space of dimension n = (vector-length vect), the coordinates are uniformly distributed within the unit n-sphere. The sum of the squares of the numbers is returned.

 random:uniform [state] Scheme Procedure scm_random_uniform (state) C Function
 Return a uniformly distributed inexact real random number in [0,1).

 seed->random-state seed Scheme Procedure scm_seed_to_random_state (seed) C Function
 Return a new random state using seed.