h43r.html

Function: fixD - prepare a function for differentiation with D

Calling sequence:

fixD(f)

Parameters:

f - a procedure name

Description:

This procedure is a work-around for a weakness in the differentiation operator D : when a function f is defined using a second user-defined function g , D(f) doesn't work. What is needed is a procedure named `diff/g` that performs the differentiation of g .

The command fixD(f) applies makediff to all user-defined procedures g referenced in f , defining a procedure `diff/g` for each of them, and thus allowing D(f) to work.

This works only for global procedures, not local procedures or module exports.

If some of the procedures g referenced in f can't be differentiated with respect to all their arguments, you should use the two-argument form of makediff on those procedures.

This function is part of the Maple Advisor Database.

Examples:

Defining f using defined function g :

> f:= x -> x*g(x^2);
g:= x -> 1 + x^2;

D(f) does not work:

> D(f);

Using fixD(f) to make this work:

> fixD(f); D(f);

Another function h defined using both f and g .

> h:= (x,y) -> f(x) + g(y); D[1](h);

Using fixD(h) to make D[1](h) work:

> fixD(h); D[1](h);

See also:

D , diff , makediff , Problems with D

Maple Advisor Database R. Israel, 2001