From: Tim Hunter <TimHunter@...>
Date: 2008-03-30T08:22:16+09:00
Subject: Re: Extrange behaviour using "if XXX ..." and "XXX if ..."

I単aki Baz Castillo wrote:
> Hi, note the difference in those both cases:
> 
> a)
> if a="QWEQWE" : a end
> => "QWEQWE"
> 
> b)
> a if a="QWEQWE"
> NameError: undefined local variable or method `a' for main:Object
> 
> 
> I know that the behaviour in a) is no recommended and maybe deprecated in a 
> future, but why it works in a) and not in b) ?

A method call without parentheses and a plain variable look the same, so 
Ruby tries to determine between the two by looking for an assignment as 
it parses your script. If it sees you assigning a value to "a", then it 
knows that "a" is a variable, otherwise it assumes that "a" is a method 
call. Parsing occurs from the top down and from left to right.

In case (a) the assignment to "a" occurs before any other reference, so 
Ruby knows it's a variable.

In case (b), there has not yet been an assignment before the reference 
to a, so Ruby assumes that "a" is a method call, yet there is no 
definition for a so you get the message.


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