From: tamouse mailing lists <tamouse.lists@...>
Date: 2013-03-26T03:41:59+09:00
Subject: Re: Confusion with Array#map

On Mon, Mar 25, 2013 at 1:37 PM, Love U Ruby <lists@ruby-forum.com> wrote:
> Joel Pearson wrote in post #1103136:
>> map iterates through the given array and collects the results with a
>> block executed on them, in this case interpreting the argument symbol
>> :capitalize into a proc { |s| s.capitalize }
>
>
> How `proc` object is getting called by `call` to produce the output? Who
> is calling that?

The operator "&" is the block operator, which is turning the symbol
:capitalize which refers to the method capitalize in that context.
Since at that point, map is sending in strings, it says to call the
capitalize method on that string.
https://en.wikibooks.org/wiki/Ruby_Programming/Syntax/Method_Calls#The_Ampersand_Operator