From: Mark Sparshatt <msparshatt@...>
Date: 2004-05-20T05:53:23+09:00
Subject: Re: Zero is true ... whoda thunk?

Jamis Buck wrote:

> Steven@ruby-lang.org wrote:
>
>> Jamis Buck <jgb3@email.byu.edu> writes:
>>
>>> I'm SO glad that Ruby forces you to compare numbers explicitly, 
>>> instead of implicitly converting to bool. It makes code that much 
>>> more readable.
>>
>>
>>
>> It doesn't, though.  This code will always print "foo":
>>     a = SomethingReturningANumber()
>>     if (a)    # Probably meant to say "a != 0", or maybe "a == 0"
>>     puts "foo"
>>     end
>> I think it _should_ force you to compare numbers explicitly -- 
>> comparisons
>> should raise exceptions if passed anything other than booleans.  But 
>> it's
>> too late for such a change.
>> -- 
>>     Steven
>> "No egg nog!  In fact, no nog, period!"
>
>
> Sorry -- I mispoke. My "force" I meant that Ruby requires you to do 
> explicit numeric comparisons for your conditions to work correctly, 
> not that it actually enforces that programming practice. You're right, 
> though. It would be nice if Ruby enforced that.
>
The problem with this there are a number of methods which return a 
numeric value of true and nil for false.

e.g. the =~ operator returns the position of the substring that matches 
the regexp, or nil if it fails to match. If either you disallowed 
numeric values, or made zero a false value, in a boolean context then 
this behaviour would have to change to allow

if(/abc/ =~ "abc")
...
end

--
Mark Sparshatt