From: John Joyce <dangerwillrobinsondanger@...>
Date: 2007-10-17T12:14:17+09:00
Subject: Re: Compound conditionals in case when statements? Syntax?


On Oct 16, 2007, at 6:37 PM, Michael Fellinger wrote:

> On 10/17/07, Randy Kramer <rhkramer@gmail.com> wrote:
>> I need (or want ;-) to do something like the following:
>>
>> when ((/^---\+\+ (.*)/) and (new_record == true))
>>
>> I've tried a lot of variations, but either this just won't work,  
>> or I haven't
>> managed to guess the proper syntax.  (I've also tried googling and  
>> searching
>> in the pickaxe(2).)
>>
>> Aside: Maybe the compound won't work because one is what the  
>> pickaxe calls a
>> condition and the other is a comparison?  But, I'm not sure which  
>> is which.
>>
>> If this can't work, I'll try (I've been trying) a nested if  
>> statement, but
>> I'll ask about that in my next post. ;-)
>
> this can't work for the simple reason that the objects given at 'when'
> are being sent the === message with the object in 'case'. In your
> 'when' it's the result of the stuff in closures.
> This generally is the job of 'if', just keep in mind that case/when is
> for matching, if/else is for conditionals.
> One roundabout way exists to make this work though:
>
> class Proc
>   def ===(obj)
>     self[obj]
>   end
> end
>
> case 'foo'
> when lambda{|e| new_record and /^---\+\+ (.*)/ === e }
>   puts :aye_match
> else
>   puts :sorry_you_lose
> end
>
> This is generally only advised if your middle name is some form of
> (Advent|Dang)erous, I won't be able to take responsibility for all
> resulting damage. But also note that new_record being true or false
> makes it simple to work with it without first comparing true/false
> with true, the result won't change, true cannot become any more true.
>
> a = true
> # true
> puts "hey" if a == true
> hey
> # nil
> puts "hey" if a
> hey
>
> Hope this helps a little bit. Have fun with ruby!
>
> ^ manveru
>
Adventerous? That's a strange middle name... ;)