Randomized aggregates

This module implements randomized version of aggregates predicates.

Example 1:

?- random_findall(4, X, between(1,10000,X), Xs).

Xs = [6659,7135,7871,9864] ? 

yes

Example 2:

?- random_findall(4, X, member(X, [the,sequel,will,not,happen]), Xs).

Xs = [the,sequel,will,happen] ? 

yes

Usage and interface

Library usage:
:- use_module(library(random_aggregates)).
Exports:
- Predicates:
  random_findall/4.

Documentation on exports

PREDICATErandom_findall/4

random_findall(K,X,Goal,Ys)

This predicate implements the reservoir sampling algorithm. It needs to evaluate all solutions to Goal but only need to keeps K of those solutions in memory simultaneously.

Usage:random_findall(K,X,Goal,Ys)

Obtains a list Ys of length K of random solutions uniformly distributed from X for all solutions to Goal. Fails if there are less than K solutions.

The following properties should hold at call time:
(term_typing:nonvar/1)K is currently a term which is not a free variable.
(term_typing:nonvar/1)X is currently a term which is not a free variable.
(term_typing:nonvar/1)Goal is currently a term which is not a free variable.

Meta-predicate with arguments: random_findall(?,?,goal,?).

Documentation on imports

This module has the following direct dependencies:

System library modules:
native_props, datafacts_rt, aggregates, random.
Packages:
prelude, initial, condcomp, assertions, assertions/assertions_basic, isomodes, nativeprops, hiord, datafacts.