Proc/Method Chains

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Cower	Created : 24 July 2009 Language : Delphi/Pascal Proc/Method Chains Code to allow chaining of proc/method calls together
Essentially, this allows you to chain method calls together either using conditions or by passing the result of one proc to the next proc. Some short examples: # Example of proc chaining puts( ( proc() {\|ab\| "foo, #{ab}"} + \ proc() {\|ab\| "#{ab}, bar"} + \ proc() {\|ab\| "[#{ab}]"} )["wimbleton"] ) # Example of conditional proc chaining begins_dot = proc do \|entry\| /^\./ === entry end Dir.chdir(File.expand_path('~')) do entries = Dir.entries('.') # get everything that begins with a dot and is not a directory proc_obj = ~File.method(:directory?) & begins_dot entries = entries.select(&proc_obj) puts entries end --v And the chaining code itself: #!/usr/bin/env ruby -wKu module ProcChainMethods # !s the result of a proc def ~ (self.kind_of?(Proc) ? self.class : Proc).new { \|args\| not self.call(args) } end # chains procs together using \|\| - the same arguments are passed to both procs/methods, unlike the +/chain methods def \| (b) raise ArgumentError, "Left proc is nil" if b.nil? raise ArgumentError, "Cannot call left object" unless b.respond_to?(:call) clas = (self.kind_of?(Proc) ? self.class : Proc) (self.kind_of?(Proc) ? self.class : Proc).new { \|args\| b.call(args) unless self.call(args) } end # chains procs/methods together using && - the same arguments are passed to both procs/methods, unlike the +/chain methods def & (b) raise ArgumentError, "Left proc is nil" if b.nil? raise ArgumentError, "Cannot call left object" unless b.respond_to?(:call) clas = (self.kind_of?(Proc) ? self.class : Proc) (self.kind_of?(Proc) ? self.class : Proc).new { \|args\| b.call(args) if result = self.call(args) } end # chains procs together without any conditions, passing the results of the first proc to the second proc # same as "return ProcB(ProcA(args))" def + (b) raise ArgumentError, "Left proc is nil" if b.nil? raise ArgumentError, "Cannot call left object" unless b.respond_to?(:call) clas = (self.kind_of?(Proc) ? self.class : Proc) (self.kind_of?(Proc) ? self.class : Proc).new { \|args\| b.call(self.call(args)) } end # synonym for ~self def invert return ~self end # synonym for self \| other \| another \| more def or_chain(args) return args.inject(self) {\|a,b\| a\|b} end # synonym for self & other & another & more def and_chain(args) return args.inject(self) {\|a,b\| a&b} end # synonym for self + other + another + more def chain(*args) return args.inject(self) {\|a,b\| a+b} end end class Proc include ProcChainMethods end class Method include ProcChainMethods end --v

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Proc/Method Chains

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