From: Francisco Laguna <fla@...>
Date: 2007-06-15T06:48:52+09:00
Subject: Re: "case when" executes a symbol as method

Thanks David and Devin for pointing that out! Looks like the syntax  
highlighting in my editor tricked my head into parsing that weirdly  :D

Am 14.06.2007 um 16:16 schrieb dblack@wobblini.net:

> Hi --
>
> On Thu, 14 Jun 2007, Francisco Laguna wrote:
>
>> Hi List!
>>
>> I just stumbled upon some interesting behaviour of case when and  
>> wanted
>> to ask a few things about it. It looks like the "case when" construct
>> executes a method when one leaves a out a newline (or semi-colon, I
>> guess) after the when differentiation. Consider these to programs:
>>
>> === program 1 ===
>>
>> def hello
>>  "Hello World!"
>> end
>>
>> def good_day
>>  "Good Day, World!"
>> end
>>
>> greeting = "Hello"
>>
>> puts case greeting
>> when "Hello"
>>  :hello
>> when "Good Day"
>>  :good_day
>> end
>>
>> === program 2 ===
>>
>> def hello
>>  "Hello World!"
>> end
>>
>> def good_day
>>  "Good Day, World!"
>> end
>>
>> greeting = "Hello"
>>
>> puts case greeting
>> when "Hello" :hello
>> when "Good Day" :good_day
>> end
>>
>> ==============
>>
>> The first just prints out the symbols turned to strings ("hello" or
>> "good_day", respectively), but the second one acrually executes the
>> hello and good_day methods and the case block has the return value of
>> the methods as its own value. Pretty cool, if you ask me. How  
>> come? Is
>> that something I can rely on, or something that might disappear,  
>> because
>> it's just some side-effect?
>
> I believe it's being parsed as:
>
>   when "Hello": hello
>
> Note the : which can also separate the when part from the value.
>
> Don't be disappointed.  It would be beyond bizarre if a symbol
> suddenly decided to be a method call because of something like which
> line it was written on.
>
>
> David
>
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