From: Rando Christensen <eyez@...>
Date: 2004-08-05T06:16:52+09:00
Subject: Re: Macros in Ruby

Jesse Jones wrote:
>>>percent-case
>>>  0.75 case
>>>    normal_hit
>>>  end
>>>
>>>  0.20 case
>>>    critical_hit
>>>  end
>>>
>>>  otherwise
>>>    kill_foe
>>>  end
>>>end
>>
>>I'm sorry, but I don't see how this is more readable than:
>>
>>  case hit_roll
>>    when (0.0 .. 0.75)
>>      normal_hit
>>    when (0.75 .. 0.95)
>>      critical_hit
>>    else
>>      kill_foe
>>    end
>>  end
> 
> 
> A macro (or some clever code like Joel's) is better in two ways:
> 
> 1) It's much easier to glance at numbers like 0.75 and 0.20 and figure
> out the relative weighting. For me at least, it's a fair amount harder
> to subtract two sets of numbers and compare them. Of course, you could
> add comments listing the percentages, but it's always preferable to
> rewrite the code so that it doesn't need such comments.

I don't think you're right on this point. In the case that was
presented:

 >   0.75 case
 >     normal_hit
 >   end

Does this mean 0.75 and above, or 0.75 and below? You won't know
this unless you look up the macro's definition. Here, however:

 >    when (0.0 .. 0.75)
 >       normal_hit

I don't think you can be confused on that point.

The macro version has made the code much less clear in my mind, which is
precisely the argument against macros in ruby.

-- 
Rando Christensen
<eyez@illuzionz.org>