From: Joshua Ballanco <jballanc@...>
Date: 2011-04-25T23:59:50+09:00
Subject: [ruby-core:35881] [Ruby 1.9 - Bug #4610] Proc#curry behavior is inconsistent with lambdas containing default argument values


Issue #4610 has been updated by Joshua Ballanco.


Appologies for the formatting mistakes...


If I curry a lambda with 3 arguments, then I can call three times with one argument each time to get the desired results:

 ruby-1.9.2-p180 :001 > l = ->(a, b, c) { puts "#{a}, #{b}, #{c}" }
 ruby-1.9.2-p180 :002 > c = l.curry
 ruby-1.9.2-p180 :003 > c.('one').('two').('three')
 one, two, three nil
 
However, if the lambda has default values and I curry it, the entire lambda is evaluated after the first #call:

 ruby-1.9.2-p180 :004 > l = ->(a = 'ichi', b = 'ni', c = 'san') { puts "#{a}, #{b}, #{c}" }
 ruby-1.9.2-p180 :005 > c = l.curry
 ruby-1.9.2-p180 :006 > c.('one').('two').('three')
 one, ni, san
 NoMethodError: undefined method `call' for nil:NilClass
  
This behavior seem very inconsistent. Ideally, if I wanted to use the default argument at a certain position in a currie proc, I would just #call with no arguments, like so:

 ruby-1.9.2-p180 :007 > c.('one').().('three')
 #=> Propose that this should result in: "one, ni, three"
----------------------------------------
Bug #4610: Proc#curry behavior is inconsistent with lambdas containing default argument values
http://redmine.ruby-lang.org/issues/4610

Author: Joshua Ballanco
Status: Open
Priority: Normal
Assignee: 
Category: 
Target version: 
ruby -v: 1.9.2p180


If I curry a lambda with 3 arguments, then I can call three times with one argument each time to get the desired results:

ruby-1.9.2-p180 :001 > l = ->(a, b, c) { puts "#{a}, #{b}, #{c}" }
#<Proc:0x00000100963650@(irb):1 (lambda)>
ruby-1.9.2-p180 :002 > c = l.curry
#<Proc:0x0000010095c9e0 (lambda)>
ruby-1.9.2-p180 :003 > c.('one').('two').('three')
one, two, three
nil

However, if the lambda has default values and I curry it, the entire lambda is evaluated after the first #call:


ruby-1.9.2-p180 :004 > l = ->(a = 'ichi', b = 'ni', c = 'san') { puts "#{a}, #{b}, #{c}" }
#<Proc:0x00000100877b88@(irb):4 (lambda)>
ruby-1.9.2-p180 :005 > c = l.curry
#<Proc:0x0000010086b338 (lambda)>
ruby-1.9.2-p180 :006 > c.('one').('two').('three')
one, ni, san
NoMethodError: undefined method `call' for nil:NilClass

This behavior seem very inconsistent. Ideally, if I wanted to use the default argument at a certain position in a currie proc, I would just #call with no arguments, like so:

ruby-1.9.2-p180 :007 > c.('one').().('three')
#=> Propose that this result in: "one, ni, three"


-- 
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