Re: exist, configure, doc2tex and \index

[Ethan A M. <merritt@u.washington.edu>]

On Sunday 13 August 2006 01:47 pm, Petr Mikulik wrote:
> gnuplot> print words(4)
>           internal error : non-STRING argument 
> gnuplot> print exists(4)
> 0
> 
> Shouldn't we expect the same error message?
> (and "internal error: ...", not "... error : ...")

Maybe.  I'm not sure.
The important thing is the return value, not the error message.

Consider the patch
###################################################################
--- gnuplot/src/standard.c      2006-07-15 19:14:01.000000000 -0700
+++ gnuplot-cvs/src/standard.c  2006-08-13 14:52:24.000000000 -0700
@@ -989,6 +989,7 @@
        gpfree_string(&a);
        push(Ginteger(&a, udv->udv_undef ? 0 : 1));
     } else {
+       int_warn(NO_CARET,"internal error : non-string argument");
        push(Ginteger(&a, 0));
     }
 #endif
###################################################################
With this patch in place, you now see

gnuplot> print exists(foo)
         undefined variable: foo
gnuplot> print exists(89)
         warning: internal error : non-string argument
0
gnuplot> foo = 89
gnuplot> print exists(foo)
         warning: internal error : non-string argument
0

So with the patch it does print "non-string argument" as
a warning.  But should it return 0, or 1?  At this point we
do know that there was a variable "foo", even if the query
contained a syntax error. It is complicated by the question
of recursion:

gnuplot> foo = "var"
gnuplot> print exists(foo)
0
gnuplot> var = 89
gnuplot> print exists(foo)
1

In this example foo is a defined variable, but is the lack
of quotes an unintentional syntax error, or is it an intended
indirect query?  There is no way of knowing.

Daniel Sebald wrote
> Is this 4.2 critical, Ethan? 
> Otherwise, we can create a bug report and come back to it. 

But I don't actually think it's a bug.
At worst you could call it a lack of an error message.

But as the example above shows (and you gave a similar one)
it is not always an error to pass an unquoted variable name.
So although the error message is strictly speaking correct,
it may still be confusing.

-- 
Ethan A Merritt
Biomolecular Structure Center
University of Washington, Seattle 98195-7742