[EMAIL PROTECTED] (John W. Krahn) writes:
> "Michael R. Wolf" wrote:
> >
> > [EMAIL PROTECTED] (John W. Krahn) writes:
> > >
> > > Are you sure there are only three? :-)
> > >
> > > $ perl -le'
> > > print qq(undef is FALSE) unless undef;
> > > print qq("" is FALSE) unless "";
> > > print qq("0" is FALSE) unless "0";
> > > print qq(0 is FALSE) unless 0;
> > > print qq(0e0 is FALSE) unless 0e0;
> > > '
> > > undef is FALSE
> > > "" is FALSE
> > > "0" is FALSE
> > > 0 is FALSE
> > > 0e0 is FALSE
> >
> > You caught me; very nice counterproof. You were obvoiusly
> > right about the "0" (see "Camel citation below), but I'd
> > suggest that 0 and 0e0 are the same - they're both scalar
> > numeric zero. I could be convinced otherwise if there's a
> > reason to make the distinction between these:
> >
> > scalar numeric float zero (0e0)
> > scalar numeric int zero (0)
> >
> > I originally suggested 3 false values, you counterproposed
> > 5, and now I'm counter-counterproposing 4.
> >
> > I've modified the test (with answers) as below.
> >
> > test> Any value that is not false is true. What values indicate false?
> > test>
> > test> string -- _""____ _"0"___
> > test>
> > test> numeric -- _0_____
> > test>
> > test> other -- _undef_
> > test>
> >
> > When scoring it, I'll accept 0e0 instead of or in addition
> > to 0, but I'm not likely to get it since I won't mention the
> > distinction in class. There isn't really an user-level
> > distinction between int and float like there is a
> > distinction between string/numeric and scalar/array.
>
> The reason I threw in the 0e0 is that although 0 stringified is also
> false this is not true for "0e0" which is true.
>
> $ perl -le'
> print q("0e0" is ), "0e0" ? "TRUE" : "FALSE";
> print q( 0e0 is ), 0e0 ? "TRUE" : "FALSE";
> '
> "0e0" is TRUE
> 0e0 is FALSE
Camel> Truth in Perl is always evaluated in a scalar
Camel> context. (Other than that, no type coercion is done.) So
Camel> here are the rules for the various kinds of values that a
Camel> scalar can hold:
Camel>
Camel> Any string is true except for "" and "0".
Camel>
Camel> Any number is true except for 0.
Camel>
Camel> Any reference is true.
Camel>
Camel> Any undefined value is false.
Camel> Any string is true except for "" and "0".
You have demonstrated string non-false with the specific
string "0e0".
Camel> Any number is true except for 0.
But you have not shown that 0 and 0e0 different cases of
numeric non-false.
Can you show that stringify(0) and stringify(0e0) (or any
other path that starts with different numeric literals)
yield different results vis-a-vis the only false string
values ("" and "0")?
If not, I re-assert that there are 4 false values and that
every thing else is true.
""
"0"
0
undef
--
Michael R. Wolf
All mammals learn by playing!
[EMAIL PROTECTED]
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
