Which one is a Ruby deprecated proc?

Question

In the book Programming Ruby: The Pragmatic Programmers Guide by Dave Thomas with Chad Fowler and Andy Hunt, regarding the creation of Procs there is a footnote that states:

"There’s actually a third, proc, but it is effectively deprecated."

I could not find which way is this. I am aware of the following ways to create a Proc:

1

b = lambda { | msg | puts "msg: #{msg}" }
b.call("hi")

2

def create_block_object(&block)
  block
end
b = create_block_object{ |msg| puts "msg: #{msg}" }
b.call("hello")

3

b = Proc.new { |msg| puts "msg: #{msg}"}
b.call("hey")

I want to know the fourth way and would be glad if somebody would give me an answer.

@fmendez thanks for response. It's what a book says at a footnote `6. There’s actually a third, proc, but it is effectively deprecated.` @sawa big thanks for an edit — Davit, Mar 17 '13 at 15:54
Number 1 is deprecated since Ruby 1.9 in favor of the notation in davidrac's answer. — sawa, Mar 17 '13 at 15:56
@sawa: do you have a source for `lambda` being deprecated? It's clear from Black's book that the `Kernel#proc` method is the one he means. — echristopherson, Mar 18 '13 at 00:33

score 1 · Answer 1 · answered Mar 17 '13 at 15:53

1

This is another syntax for lambdas:

b = ->(msg) { puts "msg: #{msg}" }
b.call("hi")

answered Mar 17 '13 at 15:53

davidrac

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thanks, I know that, it is also present since Ruby 1.9 and it is not really deprecated, I guess – Davit Mar 17 '13 at 15:55

Cezar · Accepted Answer · 2013-03-28T17:51:18.077

1

The book you are referring to is on Ruby 1.8.

In that version of Ruby, lambda and procs are effectively aliases, while Proc is a different beast. This is obviously misleading, which is why it is not recommended that you use proc as in

prc = proc {|x, y| puts x + y}

This syntax is considered deprecated and it is recommended using lambda in this case.

This is no longer valid for later versions of Ruby, starting with 1.9.

edited Mar 28 '13 at 17:51

answered Mar 17 '13 at 16:03

Cezar

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thanks, I found out that you were right since book never mentioned a method you provided – Davit Mar 17 '13 at 16:04
1

Actually, `Kernel#proc` is equivalent to `Kernel#lambda` before Ruby 1.9, and equivalent to `Proc.new` in 1.9 (not sure about 2.0). For this reason Black cautions against using it (since the semantics of lambda and non-lambda `Procs` are different). This is written in a footnote in the section "Blocks, Closures, and Proc Objects" in Chapter 22 ("The Ruby Language"). – echristopherson Mar 18 '13 at 00:46

score 0 · Answer 3 · answered Aug 06 '14 at 18:49

0

prc = proc {|x| x*x} has been depreciated.

This syntax was process was predominantly used in Ruby-1.8.7 versions.

answered Aug 06 '14 at 18:49

kapiltekwani

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Which one is a Ruby deprecated proc?

3 Answers3