From: ozaki@... Date: 2017-08-31T06:26:32+00:00 Subject: [ruby-core:82555] [Ruby trunk Feature#6284] Add composition for procs Issue #6284 has been updated by yuroyoro (TOMOHITO Ozaki). Most languages do not define function composition in built-in operators, but provide them as function or method such as `compose`. F.Y.I) https://rosettacode.org/wiki/Function_composition In some few languages defined function composition operator as following. haskell : `.` F# : `<<` and `>>` Groovy : `<<` and `>>` I think Ruby should proivide `compose` method (and `and_then` as forward composition), and alias some operator (like `#<<` or `#*) to them. In my opinion, +1 for `<<` and `>>` instead of `*`. Because there is no language define function composition as `*` and `+`, but F# and groovy defined as `<<` and `>>`. It is intutive. By the way, It is useful if `Symbol#<<` (or `Symbol#+`) is shortcut method to `sym.to_proc.compose(other_proc)`. ``` arr.map(&:upcase.to_proc.compose(:to_s.to_proc)) arr.map(&:to_s >> :upcase) ``` It is more visually and intuitive. My reference implemenation of composition is following. https://github.com/yuroyoro/ruby/pull/7 ---------------------------------------- Feature #6284: Add composition for procs https://bugs.ruby-lang.org/issues/6284#change-66365 * Author: pabloh (Pablo Herrero) * Status: Feedback * Priority: Normal * Assignee: matz (Yukihiro Matsumoto) * Target version: ---------------------------------------- =begin It would be nice to be able to compose procs like functions in functional programming languages: to_camel = :capitalize.to_proc add_header = ->val {"Title: " + val} format_as_title = add_header << to_camel << :strip instead of: format_as_title = lambda {|val| "Title: " + val.strip.capitalize } It's pretty easy to implement in pure ruby: class Proc def << block proc { |*args| self.call( block.to_proc.call(*args) ) } end end =end ---Files-------------------------------- 0001-proc.c-Implement-Proc-for-Proc-composition.patch (3.65 KB) 0002-proc.c-Implement-Method-for-Method-composition.patch (2.67 KB) 0003-proc.c-Support-any-callable-when-composing-Procs.patch (3.97 KB) -- https://bugs.ruby-lang.org/ Unsubscribe: