# Flow of execution

**URL:** <https://www.ruby-forum.com/t/flow-of-execution/83733>\
**Category:** Ruby\
**Created:** [January 29, 2007, 10:45am UTC](https://www.ruby-forum.com/t/flow-of-execution/83733 "2007-01-29T10:45:20Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![marksbrain](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/6bbea6/32.png) [@marksbrain](https://www.ruby-forum.com/u/marksbrain)\
**Post date:** [January 29, 2007, 10:45am UTC](https://www.ruby-forum.com/t/flow-of-execution/83733/1 "2007-01-29T10:45:20Z")

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Hi all,

Could someone explain the ‘flow’ of how the eg below is processed?  
My limited understanding is that the left hand side is the receiver and  
the right hand side the method being passed to the receiver?

What I don’t understand is where the block comes into the equation for  
something like the following:

values = anagrams.values.sort do |a, b|  
b.length \<=\> a.length  
end

The block changes how the sort method sorts? ie it sorts by length  
rather  
than alphabetically? So it overrides the default meaning of \<=\>??

We get the values of the anagram hash by the ‘values’ method?  
We then do:

.sort do |a, b| b.length \<=\> a.length end

ie this whole line acts on the values array??  
not a 2 step process of 1. the sort method then 2. the block applied in  
some way?

To illustrate what I’m failing dismally to explain here:  
Using () for grouping, is it processed as A or B?

A  
values = anagrams.values.(sort do |a, b| b.length \<=\> a.length)  
end

B  
values = anagrams.values.(sort) (do |a, b| b.length \<=\> a.length)  
end

thanks,

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<div class="post-metadata">

**Author:** ![marksbrain](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/6bbea6/32.png) [@marksbrain](https://www.ruby-forum.com/u/marksbrain)\
**Post date:** [January 29, 2007, 11:10am UTC](https://www.ruby-forum.com/t/flow-of-execution/83733/2 "2007-01-29T11:10:24Z")

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Mark W. wrote:

> b.length \<=\> a.length
> 
> ie this whole line acts on the values array??  
> not a 2 step process of 1. the sort method then 2. the block applied in  
> some way?
> 
> To illustrate what I’m failing dismally to explain here:  
> Using () for grouping, is it processed as A or B?
> 
> A  
> values = anagrams.values.(sort do |a, b| b.length \<=\> a.length)  
> end  
> This, almost. It’s more like:

values = anagrams.values.sort(do |a,b| b.length \<=\> a.length end)

The block essentially acts as a parameter to the sort method. The sort  
method uses the result of passing each pair to the block to perform the  
actual sorting.

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**Author:** ![marksbrain](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/6bbea6/32.png) [@marksbrain](https://www.ruby-forum.com/u/marksbrain)\
**Post date:** [January 29, 2007, 11:26am UTC](https://www.ruby-forum.com/t/flow-of-execution/83733/3 "2007-01-29T11:26:25Z")

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Hi Alex,

On Mon, 29 Jan 2007 19:09:35 +0900, Alex Y. wrote:

> > values = anagrams.values.sort do |a, b|  
> > .sort do |a, b| b.length \<=\> a.length end  
> > end  
> > This, almost. It’s more like:
> 
> values = anagrams.values.sort(do |a,b| b.length \<=\> a.length end)
> 
> The block essentially acts as a parameter to the sort method. The sort  
> method uses the result of passing each pair to the block to perform the  
> actual sorting.

excellent, thanks.