# The difference between for-loop and each

**URL:** <https://www.ruby-forum.com/t/the-difference-between-for-loop-and-each/117745>\
**Category:** Ruby\
**Created:** [October 19, 2007, 9:21pm UTC](https://www.ruby-forum.com/t/the-difference-between-for-loop-and-each/117745 "2007-10-19T21:21:14Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\
**Post date:** [October 19, 2007, 9:21pm UTC](https://www.ruby-forum.com/t/the-difference-between-for-loop-and-each/117745/1 "2007-10-19T21:21:14Z")

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Hopefully (I’m sure) somebody can shed a light on this. This caught me  
by surprise

test.rb:  
TEST = []  
def procs &block  
TEST \<\< block  
end

#for n in [1,2,3] do  
[1,2,3].each do |n|  
procs do  
puts “#{n}”  
end  
end

TEST.each do |t|  
puts t  
t.call  
end

With for loop

> > ruby test.rb

# 

3

# 

3

# 

3

With each

> > ruby test.rb

# 

1

# 

2

# 

3

I thought for-loop behaves the same as each. Apparently not. Why is this  
and is this a good thing?

Thank you in advance  
-andre

---

<div class="post-metadata">

**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\
**Post date:** [October 20, 2007, 11:30am UTC](https://www.ruby-forum.com/t/the-difference-between-for-loop-and-each/117745/2 "2007-10-20T11:30:57Z")

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On 19.10.2007 21:19, Andreas S wrote:

> procs do
> 
> > > ruby test.rb  
> > > 1
> 
> # 
> 
> 2
> 
> # 
> 
> 3
> 
> I thought for-loop behaves the same as each. Apparently not. Why is this and is this a good thing?

The reason for the behavior you are seeing is different scoping. “for”  
does not open a new scope while block parameters sit in a different  
scope. Apart from that “for” is a keyword (i.e. part of the language)  
while “each” is just a method like other methods.

irb(main):014:0\> def f1(x) x.each {|y| p y}; p y end  
=\> nil  
irb(main):015:0\> def f2(x) for y in x; p y; end; p y end  
=\> nil  
irb(main):016:0\> f1 %w{foo bar baz}  
“foo”  
“bar”  
“baz”  
NameError: undefined local variable or method `y' for main:Object from (irb):14:in`f1’  
from (irb):16  
from :0  
irb(main):017:0\> f2 %w{foo bar baz}  
“foo”  
“bar”  
“baz”  
“baz”  
=\> nil  
irb(main):018:0\>

I’d say it’s a good thing because you get the choice - if you need the  
iteration variable after the block then use “for” - otherwise use  
“each”.

Kind regards

robert