string function: definition of a function

[James R. V. Z. <jr...@co...>]

I propose the patch below, which adds a function that returns the
string that defines a specified user defined function.

I would like to be able to put the definition of a function into a
label, like this:

  gnuplot> fun(x)=1-x**2/2
  gnuplot> set label definition('fun') at graph .05,.95
  gnuplot> plot [-1:1] fun(x),cos(x)
  
This becomes useful if the function definition is long, and/or you
want to plot it for several values of a second variable.  Without this
function, one can of course use "show functions" and cut and paste the
text into a separate "set label" command.  However, that has to be
repeated each time you change the function definition - i.e. a manual
action to keep the function definition and the label aligned.

More basically, if you have many functions, this lets you see the
definition of one without having it scrolled off the screen by a lot
of others:

  gnuplot> print definition('fun')
  fun(x)=1-x**2/2
  
The name is the simplest one I came up with.  Maybe "definitionof"
would be more descriptive.

I included basic documentation in the patch.  If it's accepted, I
would add some cross-references.

       - Jim Van Zandt


Index: src/internal.h
===================================================================
RCS file: /cvsroot/gnuplot/gnuplot/src/internal.h,v
retrieving revision 1.19
diff -u -r1.19 internal.h
--- src/internal.h	28 Aug 2007 06:13:07 -0000	1.19
+++ src/internal.h	26 Jan 2009 03:00:33 -0000
@@ -89,5 +89,6 @@
 void f_strftime __PROTO((union argument *x));
 void f_strptime __PROTO((union argument *x));
 void f_assign __PROTO((union argument *x));
+void f_definition __PROTO((union argument *x));
 
 #endif /* GNUPLOT_INTERNAL_H */
Index: src/internal.c
===================================================================
RCS file: /cvsroot/gnuplot/gnuplot/src/internal.c,v
retrieving revision 1.51
diff -u -r1.51 internal.c
--- src/internal.c	25 Sep 2008 18:33:50 -0000	1.51
+++ src/internal.c	26 Jan 2009 03:00:33 -0000
@@ -1521,3 +1521,33 @@
     }
 }
 
+/* Return the string defining the specified user function
+ * JRV Jan 2008
+ */
+void
+f_definition(union argument *arg)
+{
+    struct value a, result;
+    struct udft_entry *udf = first_udf;
+
+    pop(&a);  /* pop the argument */
+
+    /* Make sure we got a string */
+    if (a.type != STRING)
+	int_error(NO_CARET,"definition requires a string parameter");
+
+    while (udf) {
+      /* find a function with that name */
+      if (udf->definition && !strcmp(a.v.string_val, udf->udf_name)) {
+	/* push its definition string onto the stack */
+	push(Gstring(&result, udf->definition));
+	goto done;
+      }
+      udf = udf->next_udf;
+    }
+    int_error(NO_CARET,"undefined user function: %s",a.v.string_val);
+ done:
+    gpfree_string(&a);
+}
+
+
Index: src/eval.c
===================================================================
RCS file: /cvsroot/gnuplot/gnuplot/src/eval.c,v
retrieving revision 1.71
diff -u -r1.71 eval.c
--- src/eval.c	2 Sep 2008 21:17:01 -0000	1.71
+++ src/eval.c	26 Jan 2009 03:00:34 -0000
@@ -191,6 +191,7 @@
 
     {"stringcolumn",  f_stringcolumn},	/* for using specs */
     {"strcol",  f_stringcolumn},	/* shorthand form */
+    {"definition", f_definition},	/* for string variables only */
     {"sprintf",  f_sprintf},	/* for string variables only */
     {"gprintf",  f_gprintf},	/* for string variables only */
     {"strlen",  f_strlen},	/* for string variables only */
Index: docs/gnuplot.doc
===================================================================
RCS file: /cvsroot/gnuplot/gnuplot/docs/gnuplot.doc,v
retrieving revision 1.553
diff -u -r1.553 gnuplot.doc
--- docs/gnuplot.doc	4 Jan 2009 05:47:14 -0000	1.553
+++ docs/gnuplot.doc	26 Jan 2009 03:00:39 -0000
@@ -1082,6 +1082,16 @@
 %c c l .
 %Function@Arguments@Returns
 %_
+4 definition
+?expressions functions definition
+?functions definition
+?definition
+=definition
+#definition("name") & string & string defining the user function named "name" \\
+%definition("name")@string@string defining the user function named "name"
+ `definition("name")` returns the string defining the user function named
+ "name". For example, `foo(x)=x+3; definition("foo")` returns the
+ string "foo(x)=x+3".
 4 gprintf
 ?expressions functions gprintf
 ?functions gprintf