4.27 Misc arithmetic support predicates

set_random(+Option)

Controls the random number generator accessible through the functions random/1 and random_float/0. Note that the library library(random) provides an alternative API to the same random primitives.

seed(+Seed)

Set the seed of the random generator for this thread. Seed is an integer or the atom random. If random, repeat the initialization procedure described with the function random/1. Here is an example:

?- set_random(seed(111)), A is random(6).
A = 5.
?- set_random(seed(111)), A is random(6).
A = 5.

state(+State)

Set the generator to a state fetched using the state property of random_property/1. Using other values may lead to undefined behaviour.^{79The limitations of the underlying (GMP) library are unknown, which makes it impossible to validate the State.}

random_property(?Option)

True when Option is a current property of the random generator. Currently, this predicate provides access to the state. This predicate is not present on systems where the state is inaccessible.

state(-State)

Describes the current state of the random generator. State is a normal Prolog term that can be asserted or written to a file. Applications should make no other assumptions about its representation. The only meaningful operation is to use as argument to set_random/1 using the state(State) option.^{bugGMP provides no portable mechanism to fetch and restore the state. The current implementation works, but the state depends on the platform. I.e., it is generally not possible to reuse the state with another version of GMP or on a CPU with different datasizes or endian-ness.}

current_arithmetic_function(?Head)

True when Head is an evaluable function. For example:

?- current_arithmetic_function(sin(_)).
true.