From: Michel Martens <blaumag@...>
Date: 2005-02-22T23:58:40+09:00
Subject: Re: Proposal for nil, 0, and "" in an if statement

Even though I'm not sure I love globals like $\ or $*, I think the
"rule of validity" method should depend of a variable of that kind.
For instance, a global $- could be defined
and default to [nil, false, "", 0, [], {}]. That way, one could define
at runtime wich values can be declared "vapid" or "empty" or whatever
the final method name is.

Example:

price = 2
discount = 2
total = '%0.2f' %(price - discount)

$- << '0.00'

if total.valid?
 # Will never get here
end

On Tue, 22 Feb 2005 23:37:37 +0900, Gavin Kistner <gavin@refinery.com> 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.
> 
>