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Contents
module Kernel #:nodoc:
# Directive for making your functions faster by trading
# space for time. When you "memoize" a method/function
# using #once its results are cached so that later calls
# with the same arguments return results from the cache
# instead of recalculating them.
#
# class T
# def initialize(a)
# @a = a
# end
# def a
# "#{@a ^ 3 + 4}"
# end
# once :a
# end
#
# t = T.new
# t.a.__id__ == t.a.__id__ #=> true
#
# This method can also be used at the instance level
# to cache singleton/eigen methods.
#
# Note, this method used to be called +cache+ along with
# it's other alias #memoize, but +once+ is the term used
# in PickAxe so it has been adopted instead. The #memoize
# alias has also been retained.
#
# CREDIT Robert Feldt
#
def once(*ids)
if ids.empty?
@_once ||= Hash::new{|h,k| h[k]={}}
else
base = (Module === self ? self : (class << self; self; end))
ids.each do |m|
base.module_eval <<-code
alias_method '#{ m }:once', '#{ m }'
private '#{ m }:once'
def #{ m }(*__a__,&__b__)
c = once['#{ m }']
k = [__a__,__b__]
if c.has_key? k
c[k]
else
c[k] = __send__('#{ m }:once',*__a__,&__b__)
end
end
code
end
end
end
# +once+ is also widely known as +memoize+.
alias_method :memoize, :once
end
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12 entries across 12 versions & 2 rubygems