[OctDev] Re: inline functions (Corrected source)

[Paul K. <pki...@ja...>]

Sure.  Add it to octave forge.  I simplified the while loop a bit, and let
you use a default parameter of "x".  I wouldn't go much beyond this in
terms of compatibility --- too many assumptions required about what makes a
variable and what order the variables should go in. Maybe inline(expr,n) as
shorthand for inline(expr,"x","P1","P2",...,"Pn") is useful.

Paul Kienzle
pki...@us...

On Sat, Aug 10, 2002 at 06:37:46PM +0100, Etienne Grossmann wrote:
> 
>   Sorry, there was a part missing from the first attached func. Try
> the following.
> 
>   Etienne
> 
> On Sat, Aug 10, 2002 at 01:32:42PM +0000, Steffan Berridge wrote:
> # 
> # Hi,
> # 
> # I have just started using Octave, having used Matlab for a
> # while.  In Matlab I have often used inline functions, they
> # are very convenient for example when passing a function as
> # an argument.
> # 
> # For example, the following is a function returning the
> # square of the argument:
> # 
> # fun = inline('x^2','x');
> # 
> # One can then pass this function as an argument to another
> # function:
> # 
> # x = foo(fun,...);
> # 
> # So my question is, is there an equivalent construction in
> # Octave?  If not, what is the best way to pass functions as
> # arguments?
> # 
> # Thanks,
> # Steffan
> -- 
> Etienne Grossmann ------ http://www.isr.ist.utl.pt/~etienne

## [fname,fcode] = inline (str,arg1,...) - Define a function from a string
##
## INPUT : -----------
## str   : string    : String defining the result of the function
## argN  : string(s) : Names of the arguments of the function
##
## OUTPUT : ----------
## fname : string    : Name of the new function, which can e.g. be called w/
##                     feval() 
## fcode : string    : The code of the function
##
## EXAMPLE : ---------
##
## fn = inline ("x.^2 + 1","x");
## feval (fn, 6)        
##   ans = 36
##
function [fname,fcode] = inline (str,varargin)

## Choose a name (naive way : won't work zillions of times)
while 1
  fname = sprintf ("inline_func_%06i",floor (rand()*1e6));
  if exist (fname), break; end
end

## construct arg list
if nargin == 1
  argstr = "x";
else
  argstr = sprintf ("%s,",all_va_args);
  argstr = argstr(1:length(argstr)-1);
end

fcode = sprintf (["function r = %s (%s)\n",\
		  "  r = ",str,";\n",\
		  "endfunction;"],\
		 fname, argstr);
eval (fcode);
endfunction