From: Jonas Bengtsson <caelumse@...>
Date: 2002-07-09T21:19:30+09:00
Subject: Re: for ... else ... end

Hello David,
What about:

while very_time_consuming_operation
    do_something
else
    do_something_else
end


or:


while a and b and c or d and e and f and g  #and so on, i.e. a complex
                                            #condition
    do_something
else
    do_something_else
end


I know it's possible to rewrite those snippets without using an
else-construct. But I think they are easier to understand.

-- 
Best regards,
 Jonas

The brain is a wonderful organ. It starts working the moment you get
up in the morning, and does not stop until you get into the office. 
 - Robert Frost

 
Tuesday, July 09, 2002, 12:28:32 PM, you wrote:

> Hi --

> On Tue, 9 Jul 2002, Sean Chittenden wrote:

>> Hmm...  I work around not having this construct constantly when doing
>> database work.  After talking with Holden about this on IRC, I think
>> the following examples are helpful.
>>
>>
>> dbh.select_all(sql) do |row|
>>   # do something with row
>> else
>>   puts "No rows returned!"
>> end

> To me this introduces a seriously criss-crossed quality to the logic
> flow.  You'd end up with things like:

>   arr = [1,2,3,4]
>   f = arr.find_all {|n| n > 4 else puts "Not found"}

>> for elt in arr
>>   puts elt
>> else
>>   puts "No rows processed"
>> end
>>
>>
>>
>> Which opens the door for:
>>
>> for elt in arr
>>   puts elt
>> else
>>   puts "no rows"
>> ensure
>>   puts "done looping"
>> end
>>
>>
>> Hmm...  I think else is the correct word because it is short hand for
>> typing out:
>>
>> if [].length > 0
>>   for elt in []
>>     puts elt
>>   end
>> else
>>   puts "now rows"
>> end
>> puts "done looping"
>>
>> The example immediately above strikes me as a way of working around
>> the language, as opposed to the language doing what you want it to.
>> ::shrug:: My $0.02.  -sc

>   puts if arr.empty? then "no rows" else arr end
>   puts "done looping"

> (Couldn't resist :-)

> How about:

>   if arr.empty?
>     puts "no rows"
>   else
>     for elt in arr
>       # do stuff
>     end
>   end

> But in any case, I agree with Det who pointed out that this
> (determining whether a loop is executed/entered at all) is different
> from the 'break'-trapping scenario.


> David