From: James Edward Gray II <james@...>
Date: 2006-10-18T04:49:40+09:00
Subject: Re: ruby way to say this?

On Oct 17, 2006, at 2:44 PM, Louis J Scoras wrote:

> On 10/17/06, matt neuburg <matt@tidbits.com> wrote:
>> In Ruby, zero isn't false and there is no equivalent of the ?:  
>> operator
>> with the middle term omitted. So e.g. I'd like to say [pseudo-code  
>> from
>> some other language]:
>>
>> oneThing()?:otherThing()
>>
>> meaning, if oneThing is nonzero, return oneThing, else return
>> otherThing. Now, I don't want to evaluate oneThing twice, so I've  
>> ended
>> up with this:
>>
>> (temp = oneThing()).nonzero? ? temp : otherThing()
>>
>> I don't like it. Is that culturally correct, or is there a ruby  
>> way to
>> speak here, that I'm not thinking of? Thx - m.
>
>
> Are you okay with adding an extra function call?
>
> How about:
>
>    def if_zero(exp,alt)
>      exp == 0 ? alt : exp
>    end
>
>    x = 0
>
>    if_zero( (x+=1) + 1, 7) # => 2
>    if_zero(  x-=1     , 8) # => 8
>
> So your original would look like:
>
>    # if_zero(one_thing, other_thing)

If you change that to support a block, you can avoid evaluating  
other_thing unless it's needed:

def if_zero(exp)
   exp.zero? ? yield : exp
end

if_zero(one_thing) { other_thing }

James Edward Gray II