Ruby 1.9 : What is the use for Proc#yield


#1

I’m reading through Mauricio’s list of changes[0] to Ruby 1.9 and
having trouble with understanding the point of Proc#yield


Invokes the block, setting the block’s parameters to the values in
params in the same manner the yield statement does.

a_proc.yield(9, 1, 2, 3)   #=> [9, 18, 27]
a_proc.yield([9, 1, 2, 3]) #=> [9, 18, 27]
a_proc = Proc.new {|a,b| a}
a_proc.yield(1,2,3)    # => [1]

It seems like this is the same as Proc#[] or Proc#call

VERSION
=> “1.8.4”

a_proc = Proc.new {|a, b| b.collect {|i| ia }}
=> #Proc:0x00317930@:8(irb)

a_proc[9,1,2,3]
=> [9, 18, 27]

a_proc[[9,1,2,3]]
=> [9, 18, 27]

a_proc = Proc.new { |a,b| a }
=> #Proc:0x0030a44c@:11(irb)

a_proc[1,2,3]
=> 1

Mauricio says “Proc#yield was added (also NilClass#yield which raises
a LocalJumpError so you can use it on &block).”

The best ‘feature’ I can think of is that this lets you do

def something(&block)
block.yield(1,2,3)
rescue LocalJumpError
puts “was expected a block”
end

But I’m not sure I’m convinced of how cool that is. Am I missing
something?


#2

On 6/23/07, Gregory B. removed_email_address@domain.invalid wrote:

I’m reading through Mauricio’s list of changes[0] to Ruby 1.9 and
having trouble with understanding the point of Proc#yield

whoops, forgot to link.

[0] http://eigenclass.org/hiki.rb?Changes+in+Ruby+1.9


#3

On 6/24/07, Yukihiro M. removed_email_address@domain.invalid wrote:

Hi,

In message “Re: Ruby 1.9 : What is the use for Proc#yield”
on Sun, 24 Jun 2007 07:12:20 +0900, “Gregory B.” removed_email_address@domain.invalid writes:

|I’m reading through Mauricio’s list of changes[0] to Ruby 1.9 and
|having trouble with understanding the point of Proc#yield

It’s mere alias to call, just to describe the intention to invoke it
as a block passed.

Thanks for clarifying this.

-greg


#4

Hi,

In message “Re: Ruby 1.9 : What is the use for Proc#yield”
on Sun, 24 Jun 2007 07:12:20 +0900, “Gregory B.”
removed_email_address@domain.invalid writes:

|I’m reading through Mauricio’s list of changes[0] to Ruby 1.9 and
|having trouble with understanding the point of Proc#yield

It’s mere alias to call, just to describe the intention to invoke it
as a block passed.

          matz.