From: Hal Fulton <hal9000@...>
Date: 2005-02-23T09:14:39+09:00
Subject: Re: Proposal for nil, 0, and "" in an if statement

Gavin Kistner wrote:
> On Feb 22, 2005, at 7:32 AM, Gavin Kistner wrote:
> 
>> On Feb 22, 2005, at 7:19 AM, Peter Hickman wrote:
>>
>>>> I don't have actual code, but imagine looping through records 
>>>> returned with financial data, and you want to print out a "-" if the 
>>>> field is missing -or- zero. The whole "this field doesn't have any 
>>>> meaningful information that contributes to the sum of the column" 
>>>> spreadsheet thing.
>>>>
>>> Might this not cause trouble with databases. A database record (returned
>>> as a structure or object) would have NULL == nil for fields with no
>>> value which is not the same as a field with a definite value such as 0.
>>
>>
>> Yes, there are many cases where you DO want to distinguish between nil 
>> and 0. These cases are already handled by the current behavior of Ruby.
> 
> 
> To be clear - the proposal is NOT to make Ruby act like one of the many 
> other languages where "", 0 and friends are treated as non-truth values 
> in boolean expressions. The proposal is simply to add an additional 
> method to all that allows a programmer to treat them the same in the few 
> cases where that is desirable.
> 

FWIW, I once suggested the name "null?" for this.

I've always been perturbed that there is no good word which
means non-nil or non-null. A positive should be representable
as something other than a double negative IMO.


Hal