From: davidjcornu@...
Date: 2017-07-24T21:04:46+00:00
Subject: [ruby-core:82154] [Ruby trunk Feature#13765] Add Proc#bind

Issue #13765 has been reported by davidcornu (David Cornu).

----------------------------------------
Feature #13765: Add Proc#bind
https://bugs.ruby-lang.org/issues/13765

* Author: davidcornu (David Cornu)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
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`Proc` has [`curry`](https://ruby-doc.org/core-2.4.1/Proc.html#method-i-curry) but no method to do [partial application](https://en.wikipedia.org/wiki/Partial_application). Something like `Proc#bind` might be handy.

A naive implementation might look something like

~~~ ruby
class Proc
  def bind(*bound_args)
    -> (*args) { self.call(*bound_args, *args) }
  end
end
~~~

~~~ text
irb(main):001:0> foo = -> (first, second) { puts first, second }
=> #<Proc:0x007fc93a091f90@(irb):6 (lambda)>
irb(main):002:0> foo.bind(1).call(2)
1
2
=> nil
irb(main):003:0> foo.bind(1).bind(2).call
1
2
~~~

which does the job with the downside of only reporting argument mismatches when the returned `Proc` is called.

~~~
irb(main):004:0> foo3 = foo.bind(1).bind(2).bind(3)
=> #<Proc:0x007fc9378bcb00@(irb):3 (lambda)>
irb(main):005:0> foo.call
ArgumentError: wrong number of arguments (given 0, expected 2)
	from (irb):6:in `block in irb_binding'
	from (irb):35
	from /usr/local/bin/irb:11:in `<main>'
~~~





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