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##
## Datastructures: GAP package providing common datastructures.
##
## Copyright (C) 2015-2017 The datastructures team.
## For list of the team members, please refer to the COPYRIGHT file.
##
## This package is licensed under the GPL 2 or later, please refer
## to the COPYRIGHT.md and LICENSE files for details.
##
#! @Chapter Memoisation
#!
#! <Package>datastructures</Package> provides simple ways to cache return values of pure functions.
#!
#! @Section Memoisation with HashMap
#!
#! @Arguments function [, options]
#! @Returns A function
#! @Description
#! <C>MemoizeFunction</C> returns a function which behaves the same as <A>function</A>,
#! except that it caches the return value of <A>function</A>.
#! The cache can be flushed by calling <Ref Func="FlushCaches" BookName="ref"/>.
#!
#! This function does not promise to never call <A>function</A> more than
#! once for any input -- values may be removed if the cache gets too large,
#! or GAP chooses to flush all caches, or if multiple threads try to calculate
#! the same value simultaneously.
#! <P/>
#! The optional second argument is a record which provides a number
#! of configuration options. The following options are supported.
#! <List>
#! <Mark><C>flush</C> (default <K>true</K>)</Mark>
#! <Item>
#! If this is <K>true</K>, the cache is emptied whenever
#! <Ref Func="FlushCaches" BookName="ref"/> is called.
#! </Item>
#! <Mark><C>contract</C> (defaults to <Ref Func="ReturnTrue" BookName="ref"/>)</Mark>
#! <Item>
#! A function that is called on the arguments given to <A>function</A>.
#! If this function returns <K>false</K>, then <C>errorHandler</C> is
#! called.
#! </Item>
#! <Mark><C>errorHandler</C> (defaults to none)</Mark>
#! <Item>
#! A function to be called when an input that does not fulfil
#! <C>contract</C> is passed to the cache.
#! </Item>
#! </List>
#! <P/>
DeclareGlobalFunction("MemoizeFunction");
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