# What's the difference between these two block passing strate

**URL:** <https://www.ruby-forum.com/t/whats-the-difference-between-these-two-block-passing-strate/99108>\
**Category:** Ruby\
**Created:** [July 20, 2006, 10:17am UTC](https://www.ruby-forum.com/t/whats-the-difference-between-these-two-block-passing-strate/99108 "2006-07-20T10:17:04Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![maz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/e9c0ed/32.png) [@maz](https://www.ruby-forum.com/u/maz)\
**Post date:** [July 20, 2006, 10:17am UTC](https://www.ruby-forum.com/t/whats-the-difference-between-these-two-block-passing-strate/99108/1 "2006-07-20T10:17:04Z")

</div>

A common complaint I hear about Ruby is (I think, I may quoting  
incorrectly or the wrong thing) that “blocks aren’t first order object.”  
I  
won’t pretend to know what that means but, in context, it appears that  
they  
are complaining about how you can’t pass blocks around like variables.  
In  
particular, I recall someone having to deal with some kind of UI toolkit  
that requied blocks but couldn’t pass the blocks up the call stack.  
I was just fiddling around with Ruby and I think I have two ways to  
do  
this and I was wondering if there were any subtle differences between  
them  
or any gatchas that I might be missing.  
Please take a look at them. Here’s the first:

def foo  
yield  
end

def bar(&lambda)  
foo &lambda  
end

bar { puts “Blocks!” }

```
...and here's the second:

```

def foo  
yield  
end

def bar  
foo { yield }  
end

bar { puts “Blocks!” }

```
...so, what do you guys think? Are they equivalent? Is there a

```

performance difference? Are they even doing what I think they’re doing?  
Thank you…

---

<div class="post-metadata">

**Author:** ![maz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/e9c0ed/32.png) [@maz](https://www.ruby-forum.com/u/maz)\
**Post date:** [July 20, 2006, 11:01am UTC](https://www.ruby-forum.com/t/whats-the-difference-between-these-two-block-passing-strate/99108/2 "2006-07-20T11:01:32Z")

</div>

> …so, what do you guys think? Are they equivalent? Is there  
> a performance difference? Are they even doing what I think  
> they’re doing?

They are not equivalent. Version A has to convert a block into  
a Proc, which slows it down. Version B uses two calls instead  
of just one, which slows it down.

Which one wins? See below. The difference in speed is  
significant.

gegroet,  
Erik V. - [http://www.erikveen.dds.nl/](http://www.erikveen.dds.nl/)

* * *

$ cat test.rb  
require “ev/ruby”

module A  
def self.foo  
yield  
end

def self.bar(&lambda)  
foo &lambda  
end  
end

module B  
def self.foo  
yield  
end

def self.bar  
foo { yield }  
end  
end

def test(mod)  
bm mod do  
100\_000.times do  
mod.bar { :OK }  
end  
end  
end

10.times do  
test(A)  
test(B)  
end

$ ruby test.rb  
CPU ELAPSED COUNT CPU/COUNT LABEL  
18.926000 18.995000 10 1.892600 A  
2.264000 2.265000 10 0.226400 B