Function names in feval

[John W. Eaton]

On 22-Mar-2000, Dirk Laurie <address@hidden> wrote:

| In the following Octave code (2.0.14):
| 
|   function y=integ(f,a,b,n)
|   h=(b-a)/n; x=a+h*(0.5:n);
|   y=h*sum(feval(f,x));
|   endfunction
| 
| the string 'f' may not contain the name of any local variable.
| I.e. if I have coded
| 
|   function y=f(x)
|   y=exp(sin(x));
|   endfunction
| 
| it is illegal to ask for
| 
|   integ('f', 0, 2*pi, 16)
| 
| This means I have to do one of the following:
| 
| (a) use local variables with names like f_, h_ etc and tell
|     my user not to use such names.  Problem: if his routine,
|     in turn, has a function argument, he has to think up
|     another convention for his own local variables, etc. 
| 
| (b) make a list of all local variables and tell my user those
|     are illegal.
| 
| Neither is very satisfactory.  However, this must be a common
| problem which must by now have a satisfactory solution.
| 
| I'm looking for one of the following answers:
| 
| (a) "Set THE_RIGHT_GLOBAL_VARIABLE to 1 and it will ignore
|      local variables for feval."
| (b) "Install 2.0.16, in which this problem has been fixed."
| (c) "This is a standard situation, which must be handled as 
|      follows..."

Sorry, I don't have one of those answers.  I can only offer:

  (d) This looks like a bug, here is a patch to try.

jwe


2000-03-22  John W. Eaton  <address@hidden>

        * variables.cc (is_valid_function): Look in the global symbol
        table for functions.


--- src/variables.cc~   Sat Jan 29 21:00:58 2000
+++ src/variables.cc    Wed Mar 22 03:07:48 2000
@@ -263,7 +263,11 @@
   symbol_record *sr = 0;
 
   if (! fcn_name.empty ())
-    sr = lookup_by_name (fcn_name);
+    {
+      sr = global_sym_tab->lookup (fcn_name, 1, 0);
+
+      lookup (sr, 0);
+    }
 
   if (sr)
     ans = sr->def ();



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