From octave-maintainers-request at bevo dot che dot wisc dot edu  Sun Dec 17 05:34:29 2000
Subject: patch : [...] = leval(name, list)
From: Etienne Grossmann <etienne at anonimo dot isr dot ist dot utl dot pt>
To: octave-sources at bevo dot che dot wisc dot edu, octave-maintainers@bevo.che.wisc.edu
CC: etienne at isr dot ist dot utl dot pt
Date: Sun, 17 Dec 2000 11:40:14 +0000

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  Hello,

  I got convinced that a function [...] = leval(name, list) offers
more flexibility than [...] = feval(name, arg1,...,argn). For example,
such a function is useful for minimization of a function that takes
many arguments.

  I first implemented it as a leval.m which works fine, but puts an
overhead of ~4ms (PII,350MHz), which I think is too much (there may be
hundreds of calls to it).

  It turns out that "leval" is very simple to implement as a built-in:
see the patch (against 2.1.32) below. It works fine : I append a test
script too. Run it after setting "verbose=1".

  Does that patch meet the coding standards?

  Etienne


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--- parse.cc.orig	Sun Dec 17 10:45:13 2000
+++ parse.cc	Sun Dec 17 10:47:15 2000
 at @ -4836,6 +4836,50 @@
   return retval;
 }
 
+
+DEFUN (leval, args, nargout,
+  "-*- texinfo -*-\n\
+ at deftypefn {Built-in Function} {} leval (@var{name}, @var{list})\n\
+Evaluate the function named  at var{name} dot   All the elements in @var{list}\n\
+are passed on to the named function.  For example,\n\
+\n\
+ at example\n\
+leval (\"acos\", list (-1))\n\
+      at result{} 3.1416\n\
+ at end example\n\
+\n\
+ at noindent\n\
+calls the function  at code{acos} with the argument @samp{-1}.\n\
+\n\
+The function  at code{leval} provides provides more flexibility than\n\
+ at code{feval} since arguments need not be hard-wired in the calling \n\
+code.  at seealso{feval and eval}\n\
+ at end deftypefn")
+{
+  octave_value_list retval;
+
+  int nargin = args.length ();
+
+  if (nargin == 2) 
+    {
+      std::string name = args(0).string_value ();
+      if (error_state) 
+	error ("leval: first argument must be a string");
+
+      octave_value_list lst = args(1).list_value ();
+      if (error_state) 
+	error ("leval: second argument must be a list");
+
+      retval = feval (name, lst, nargout);
+
+    } 
+  else
+    print_usage ("leval");
+
+  return retval;
+}
+
+
 octave_value_list
 eval_string (const std::string& s, bool silent, int& parse_status, int nargout)
 {

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ok = 1;
if !exist ("verbose"), verbose = 0; end

function [a,b,c] = f(x,y), a=1; b=x; c=y; end

l = list (2,3);

[a,b,c] = leval ("f",l);

if a!=1 || b!=2 || c!=3,
  if verbose, printf ("test_leval : not ok\n"); end
  ok = 0;
else
  if verbose, printf ("test_leval : ok\n"); end
end

[a,b] = leval ("f",l);

if a!=1 || b!=2,
  if verbose, printf ("test_leval : not ok\n"); end
  ok = 0;
else
  if verbose, printf ("test_leval : ok\n"); end
end

a = leval ("f",l);

if a!=1,
  if verbose, printf ("test_leval : not ok\n"); end
  ok = 0;
else
  if verbose, printf ("test_leval : ok\n"); end
end

if ok && verbose,
  ntest = 1000;
  printf ("For %i function calls\n",ntest);

  mytic ();
  for i = 1:ntest, [a,b,c] = f(2,3); end
  t1 = mytic ();

  mytic ();
  for i = 1:ntest, [a,b,c] = leval ("f",l); end
  t2 = mytic ();

  mytic ();
  for i = 1:ntest, [a,b,c] = feval ("f",2,3); end
  t3 = mytic ();

  printf ("time : plain : %8.3g, leval : %8.3g, feval : %8.3g (sec)\n",\
	  t1,t2,t3);
  printf ("overhead for leval : %8.3g seconds per call\n",(t2-t1)/ntest);
  printf ("overhead for feval : %8.3g seconds per call\n",(t3-t1)/ntest);
end

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