Re: string function: definition of a function

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

On Wednesday 28 January 2009, Ethan A Merritt wrote:
> On Wednesday 28 January 2009, James R. Van Zandt wrote:
> > 
> > Ethan A Merritt <merritt@u.washington.edu> writes:
> > >On Monday 26 January 2009, James R. Van Zandt wrote:
> > >> 
> > >> I propose the patch below, which adds a function that returns the
> > >> string that defines a specified user defined function.
> > ...
> > >A couple of thoughts:
> > >
> > >It is already possible to do essentially the same thing by reversing 
> > >the order of operations and using the recently added evaluate() function:
> > >
> > >    gnuplot> def = "f(x) = 1-x**2/2"
> > >    gnuplot> evaluate(def)
> > >    gnuplot> plot [-1:1] cos(x), f(x) title def
> > 
> > This seems awkward to me.
> 
> I agree. I was just it pointing out as something that it is already possible.

Bleah. Make that "I was just pointing it out as something..."
 
> > 
> > >Another possibility is to make the function definitions visible as
> > >string variables directly, exactly as the existing variables are.
> > >
> > >    gnuplot> g(x,y) = x**2 + y**3
> > >    gnuplot> show variable GPFUN
> > >	   Variables beginning with GPFUN:
> > >	   GPFUN_g = "g(x,y) = x**2 + y**3"
> > >    gnuplot> set label GPFUN_g at graph .05, .95
> > 
> > I think this is about as handy as the definition() function.
> > It would even let us retire the "show functions" command.
> > 
> > It would be easy to create an associated string variable when
> > recording the definition of a function.

Right. Here you go:

--- gnuplot/src/command.c	2008-12-12 19:11:34.000000000 -0800
+++ gnuplot-cvs/src/command.c	2009-01-28 22:45:09.000000000 -0800
@@ -530,6 +530,15 @@ define()
 	memcpy(c_dummy_var, save_dummy, sizeof(save_dummy));
 	m_capture(&(udf->definition), start_token, c_token - 1);
 	dummy_func = NULL;	/* dont let anyone else use our workspace */
+
+	/* Save function definition in a user-accessible variable */
+	if (1) {
+	    char *tmpnam = gp_alloc(6+strlen(udf->udf_name), "varname");
+	    strcpy(tmpnam, "GPFUN_");
+	    strcat(tmpnam, udf->udf_name);
+	    fill_gpval_string(tmpnam, udf->definition);
+	    free(tmpnam);
+	}
     } else {
 	/* variable ! */
 	char *varname = gp_input_line + token[c_token].start_index;