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#!/usr/local/bin/ruby -w
#
# == extensions/continuation.rb
#
# Adds methods to the builtin Continuation class.
#
require "extensions/_base"
#
# * Continuation.create
#
ExtensionsProject.implement(Continuation, :create, :class) do
class Continuation
#
# <tt>Continuation.create</tt> offers a nicer interface for creating continuations than
# <tt>Kernel.callcc</tt>.
#
# === Example
#
# Count down from 10 to 0 using a continuation.
#
# continuation, counter = Continuation.create(10)
# puts counter
# continuation.call(counter - 1) if counter > 0
#
# Implement a workalike of <tt>Array#inject</tt> using continuations. For simplicity's
# sake, this is not fully compatible with the real <tt>#inject</tt>.
#
# class Array
# def cc_inject( value=nil )
# copy = self.clone
# cc, result, item = Continuation.create( value, nil )
# next_item = copy.shift
# if result and item
# cc.call( yield(result, item), next_item )
# elsif next_item
# cc.call( next_item, result )
# end
# result
# end
# end
#
# [1,2,3,4,5].cc_inject { |acc, n| acc + n } # -> 15
#
# === Explanation
#
# I've got no idea how it works. TODO: work it out. In particular, what do the arguments
# do? And what the hell is going on in #cc_inject???!?
#
# === See Also
#
# This method is included in the 'extensions' package primarily to support
# Binding.of_caller.
#
# === Credits
#
# <tt>Continuation.create</tt> was written and demonstrated by Florian Gross. See
# ruby-talk:94681.
#
def Continuation.create(*args, &block)
cc = nil
result = callcc { |c|
cc = c
block.call(cc) if block and args.empty?
}
result ||= args
return *[cc, *result]
end
end
end
Version data entries
19 entries across 19 versions & 4 rubygems