Re: user-defined function & string file name

[Juergen W. <wie...@fr...>]

On Tuesday 28 June 2005, Ethan Merritt wrote:
> I will consolidate the (isstring() || isstringvar()) test into a single
> call isstringvalue().  This simplifies the code, which is good.
> If/when Juergen comes up with a fully working isstringfunc(), that can be
> added at a single point in isstringvalue().

I have uploaded a patch addressing the plot/splot problem [#1231847,
str_or_express-2005-07-09.patch].  As far as I can see, it works
sensible in almost all cases.  The only known failure case is

gnuplot> x = "file"
gnuplot> f(x) = x . ".dat"
gnuplot> plot f(x)

where it assumes f(x) to be a function plot.  But anyone careless
enough to use a dummy name in such a way ...


The second patch [#1231847, get_string-2005-07-09.patch] introduces
the function isexpr().  The idea is to provide a set of functions,
which do as many work as possible.

For example:
* get_string():
   Read in string.  If there is none, int_error().
   Probably a more concise error message could be given from the
   calling function.

* try_to_get_string()
   Read in string if there is one.  If there is none, no operation.
   Implementation draft:

   save_token = c_token;
   result = NULL;
   if (isexpr()) {
      struct value a;
      const_expr(&a);
      if (a.type == STRING)
         result = a.v.string_val;
      else
         c_token = save_token;
      gpfree_string(&a);
   }

* get_number()

* try_to_get_number()

* get_number_or_string():
   Well, basically the same as const_expr() now.

* try_to_get_number_or_string()

The latter two functions would be easier to implement without the
GP_STRING_VARS conditionals.  They can also be written similar to
str_or_express(), though.

In my opinion such functions should allow for some simplification to
the current code.  What do you think?  Is this worth going on?


Juergen

PS: I won't read my mails a week or so because I'm on holiday.