[MUG] Function argument name

[MUG] Re: Function argument name
Author: Maple Group    Posted: 01/12/2000 20:14:10 GMT
>> From: Maple Group >> From: Guy-Armand Kamendje | I have somewhere the expression | Myexp=x[1]^2+x[1]*x[2]+x[3].... x[n]in the variable x[1], x[2] ..x[n] | I will like to use this expresion in oder to let maple define a function | of the form | f1:=(x[1],x[2],...x[x])->y | when passing the subscript x[i] to the function's definition, an error | message is displayed requiring a name as funtions argument. How can I | get Maple interpret the subscripts in the correct way and also evalue | the expression Myexp in the correct way within the function? | | It looks like | > v_vect[1]:= | | 2 | 1 + x[1] + x[1] x[3] + x[2] x[1] + x[4] + x[4] x[5] + x[1] x[4] | | 2 | + x[2] x[4] + x[1] + x[2] + x[2] + x[3] x[5] | | | f1:=(x[1],x[2],x[3],x[4],x[5])->v_vect; | | Error, name expected in argument list | What I'am doing wrong? | Thanks for any hint -=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=- Date: Wed, 29 Nov 2000 11:00:27 -0800 (PST) From: Robert Israel To: Subject: Function argument name There are actually two problems here. One is that you must use non-subscripted names as formal parameters of a function. The other is that you should use "unapply", not a construction such as "f:= x -> y", to make an expression into a function. The reason the latter construction won't work is the difference between global variables and formal parameters. For example: > y:= x+1; > f:= x -> y; > f(t); x+1 The x in "y:= x+1" is a global variable. This looks the same as the formal parameter x in the definition of f, but it is treated as completely different. In particular, when you say "f(t)", Maple won't substitute t for the global variable x in the value of y. Instead, you should use > f:= unapply(y, x); f(t); t+1 "unapply" does allow the use of subscripted variables (automatically changing them to non-subscripted forms). For example: > y:= x[1]^2 + x[2]*x[3]; f:= unapply(y, x[1],x[2],x[3]); 2 f := (x_1, x_2, x_3) -> x_1 + x_2 x_3 Robert Israel Department of Mathematics http://www.math.ubc.ca/~israel University of British Columbia Vancouver, BC, Canada V6T 1Z2 -=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=- Date: Wed, 29 Nov 2000 16:25:38 -0600 (CST) From: Andrzej Pindor To: Subject: Function argument name It seems that a subscripted variable cannot appear in a function definition. However, you could do something like this: breeze{60}: maple |\^/| Maple 6 (SUN SPARC SOLARIS) ._|\| |/|_. Copyright (c) 2000 by Waterloo Maple Inc. \ MAPLE / All rights reserved. Maple is a registered trademark of <____ ____> Waterloo Maple Inc. | Type ? for help. > v_vect[1]:=1 + x[1]^2+x[1]*x[3] + x[2]*x[1] + x[4] + x[4]*x[5] + x[1]*x[4] > + x[2]*x[4] + x[1] + x[2]^2 + x[2] + x[3]*x[5]; 2 v_vect[1] := 1 + x[1] + x[1] x[3] + x[2] x[1] + x[4] + x[4] x[5] + x[1] x[4] 2 + x[2] x[4] + x[1] + x[2] + x[2] + x[3] x[5] > f1:=unapply(subs(seq(x[i]=x||i,i=1..5),v_vect[1]),seq(x||i,i=1..5)); 2 f1 := (x1, x2, x3, x4, x5) -> 1 + x1 + x1 x3 + x2 x1 + x4 + x4 x5 + x1 x4 2 + x2 x4 + x1 + x2 + x2 + x3 x5 > f1(x[1],x[2],x[3],x[4],x[5]); 2 1 + x[1] + x[1] x[3] + x[2] x[1] + x[4] + x[4] x[5] + x[1] x[4] + x[2] x[4] 2 + x[1] + x[2] + x[2] + x[3] x[5] > Regards Andrzej -- Dr. Andrzej Pindor The foolish reject what they see and not what University of Toronto think; the wise reject what they think and not Information Commons what they see. Huang Po Phone: (416) 978-5045 Fax: (416) 978-7705 -=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=- Date: Wed, 29 Nov 2000 16:40:59 -0500 (EST) From: Denis Sevee To: Subject: Function argument name Just use x as the input parameter. For example, >f:=x->x[1]+x[2]: >y:=[3,8]: >f(y); 11 If you tried f:=(x[1],x[2])->x[1]+x[2] ; you would get the same error message that you reported. Denis Sevee -=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=- Date: Thu, 30 Nov 2000 12:44:13 +0100 From: Barsuhn Subject: Function argument name To: Dear Guy-Armand, use "unapply" to build up your function f1. "unapply" automatically transforms the indexed names (illegal) into "concatinated" names (legal). When you later on call your function, you may of course also use indexed names as actual parameters. This piece of code works for Maple 6 and Maple V R5.1: > v_vect[1]:=1 + x[1]^2 + x[1]* x[3] + x[2]* x[1] + x[4] + x[4]* x[5] + x[1] *x[4]+ x[2]* x[4] + x[1] + x[2]^2 + x[2] + x[3]*x[5]; > f1:=unapply(v_vect[1],x[1],x[2],x[3],x[4],x[5]); > f1(y[1],y[2],y[3],y[4],y[5]); > The error message you got is indeed somewhat misleading, as names are allowed to have index expressions. Maple 6 correctly asks for symbols (i.e. names without any index expression) as formal parameters. All the best Jurgen -- ------------------- Prof. Dr. Jurgen Barsuhn Fachhochschule Bielefeld University of Applied Sciences Fachbereich Elektrotechnik und Informationstechnik Wilhelm-Bertelsmann-Str. 10 D-33602 Bielefeld ----------- -=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=- Date: Fri, 01 Dec 2000 09:21:04 +0900 To: From: tanaka Subject: Function argument name I think that Maple qualifies that [ ] is not a suffix but a "list". So parameter list is required. Another method to make a function is to use "unapply" command. >restart: >v_vect[1]:=1+x[1]^2+x[1]*x[3]+x[2]*x[1]+x[4]+x[4]*x[5]+x[1]*x[4] > +x[2]*x[4]+x[1]^2+x[2]+x[2]+x[3]*x[5]: >unapply( v_vect[1],x[1],x[2],x[3],x[4],x[5]); In this case, we have (x_1, x_2, x_3, x_4, x_5) -> 1+2*x_1^2+x_1*x_3+x_2*x_1+x_4+x_4*x_5 +x_1*x_4+x_2*x_4+2*x_2+x_3*x_5 Even though, the expression [ ] is ,somehow, changed to "underbar", this is a function of x[1],x[2],x[3],x[4] and x[5]. For example, a process >diff(v_vect[1],x[1]); yields 4*x[1]+x[3]+x[2]+x[4]. Dr.TANAKA, Kazuo, Canon Inc., Tokyo, JAPAN

Previous by date: [MUG] Re: Stopping integration due to what?, Allan Wittkopf
Next by date: [MUG] Simplification problem, Carl Eberhart
Previous thread: [MUG] Integration bug, i think, Halvor Mehlum
Next thread: [MUG] Simplification problem, Carl Eberhart