Re: exist, configure, doc2tex and \index

[Daniel J S. <dan...@ie...>]

Ethan A Merritt wrote:
> On Sunday 13 August 2006 09:37 pm, you wrote:
> 
>>>>>Shouldn't we expect the same error message?
>>>>>(and "internal error: ...", not "... error : ...")
>>>
>>>Is this 4.2 critical?
>>
>>Yes; you've shown that exists() doesn't work properly.
>>
>>
>>>The important thing is the return value, not the error message.
>>
>>This is the correct patch! With this patch, the exists(...) works as 
>>expected.
> 
> 
> I disagree.
> 
> Before
> -------
> gnuplot> foo = 8
> gnuplot> if (!exists(foo)) print "Hi"
> Hi
> 
> After
> -----
> gnuplot> foo = "baz"
> gnuplot> if (!exists(foo)) print "Hi"
> Hi
> gnuplot> foo = 8
> gnuplot> if (!exists(foo)) print "Hi"
>          internal error : non-string argument
> 
> 
> Are you arguing that the old behaviour was wrong, and the
> new behaviour is correct?   
> 
> I think the original behaviour was correct:
> if foo does not point to the name of a variable, exists(foo)
> returns 0.  After Daniel's patch it doesn't return at all;
> it errors out.  That means you cannot use exists(foo) to
> test whether it contains the name of a variable.

Again, I see what you are saying.  However, before the patch, let's say that foo is not defined.  Then this:

gnuplot> print exists(foo)
         undefined variable: foo

should also return a 0 by the same logic that

gnuplot> foo = 8
gnuplot> print exists(foo)
0

returns a zero.  That is, foo doesn't contain the name of a variable; it doesn't contain anything because it doesn't exist.  I ask if, in fact, "exists" does intend to answer that question, i.e., Contains a variable?  Perhaps there should be another function for that, isint(), isvar().  ??

Also in the old behavior, how is one to interpret the following?

gnuplot> print exists(23)
0

That 23 doesn't contain a variable?  In one sense, 23 does exist.  It's an integer value, e.g., one types "plot 23" and gets a valid plot.

So, I'm on the fence on this one.  I don't see a convincing argument for one way over the other just yet.

Dan