From: Robert Klemme <shortcutter@...>
Date: 2008-02-04T02:24:56+09:00
Subject: Re: how does sort work?

On 03.02.2008 04:09, Chris Sepic wrote:
>> to understand this, you can think of "sort" taking a function as a 
>> parameter.  and sort() will pass 2 numbers to this function, and 
>> rearragne the elements according to the return value of -1, 0, or 1.
>>
>> that's it.  to understand it fully, you can read about "iterators" in 
>> Ruby.  where you can take a block as a function, and "yield" arguments 
>> to this function, and get back a return value.
> 
> I understand sorting and sorting algorithms - I was tripped up by the 
> function as a parameter thing. Thanks!

Yeah, a block is an anonymous function.

You can see how it works if you insert a print statement:

irb(main):001:0> a = [ "d", "a", "e", "c", "b" ]
=> ["d", "a", "e", "c", "b"]
irb(main):002:0> a.sort {|x,y| p [x,y]; x<=>y}
["d", "e"]
["e", "b"]
["d", "b"]
["a", "d"]
["c", "d"]
["b", "a"]
["a", "c"]
["b", "c"]
=> ["a", "b", "c", "d", "e"]
irb(main):003:0>

A nice quiz might be to find out the sorting algorithm based on this 
output. :-)

Kind regards

	robert