[Maxima-bugs] [ maxima-Bugs-2922933 ] Defining function from expression doesn't relate arguments

[SourceForge.net <no...@so...>]

Bugs item #2922933, was opened at 2009-12-29 19:35
Message generated for change (Comment added) made by alex108
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=104933&aid=2922933&group_id=4933

Please note that this message will contain a full copy of the comment thread,
including the initial issue submission, for this request,
not just the latest update.
Category: Lisp Core
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Rui Maciel (rui_maciel)
Assigned to: Nobody/Anonymous (nobody)
Summary: Defining function from expression doesn't relate arguments

Initial Comment:
Let's say we have the following expression:

a: (x - 1)*x*(y - 1)*y*(z - 1)*z/8;

and let's say we declare the following function:

f(x,y,z) := a;

If we pass arguments to that function, the function fails to replace the expression's variables with the value of the arguments passed to the function. For example:

(%i387) f(0,0,0);
                         (x - 1) x (y - 1) y (z - 1) z
(%o387)                  -----------------------------
                                       8

Yet, if the expression's variables are substituted in the function declaration then everything works as expected:

(%i388) f(b,c,d) := subst([x=b,y=c,z=d],a);
(%o388)          f(b, c, d) := subst([x = b, y = c, z = d], a)
(%i389) f(0,0,0);
(%o389)                                0

That extra call to subst() should not be needed in order to successfully declare a function from an expression.

----------------------------------------------------------------------

Comment By: Aleksas Domarkas (alex108)
Date: 2009-12-30 07:56

Message:
You can  successfully
declare a function from an expression:

(%i1) (x - 1)*x*(y - 1)*y*(z - 1)*z/8;
(%o1) ((x-1)*x*(y-1)*y*(z-1)*z)/8
(%i2) define(f(x,y,z),%);
(%o2) f(x,y,z):=((x-1)*x*(y-1)*y*(z-1)*z)/8
(%i3) f(0,0,0);
(%o3) 0

----------------------------------------------------------------------

You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=104933&aid=2922933&group_id=4933