From: John Joyce <dangerwillrobinsondanger@...>
Date: 2008-01-21T11:22:10+09:00
Subject: Re: Newbie Question about Array#include?


On Jan 20, 2008, at 12:13 PM, Tim Hunter wrote:

> AoP wrote:
>> Why does the "include?" method of Array end with a question mark? I
>> thought the question mark was to indicate some sort of "unexpected"
>> behavior, such as modifying the list, but it doesn't seem to in this
>> case.
>> Thanks -
>> -James
>
> You're thinking of !, not ?. There are no hard-and-fast rules, but  
> typically methods that end in ? return true or false, and methods  
> that end in ! need extra attention for one reason or another.
>
> -- 
> RMagick: http://rmagick.rubyforge.org/
> RMagick 2: http://rmagick.rubyforge.org/rmagick2.html
>
Also remember that there are some methods in some classes that do not  
have ! but do modify the receiver.
Array has .push and .pop for examples.

In many languages, equivalents of Ruby methods ending with ? are  
called predicates. They usually read like an English Yes/No or True/ 
False question.