CODEWITHSUNDEEP
prolog
kkh
kkh

Reputation: 4869

algebraic simplification in prolog

I'm reading up on prolog simplifcation of algebraic expressions and there are some parts I dont understand.

So these are the basic simplications

  x+0, x-0, 0+x, 0-x   --> x.
  x*1, x/1, 1*x        --> x.
  -1*x, x*(-1), x/(-1) --> –x.
  x+(-x)               --> x–x.

so given an expression 

 (x+4)*(2-x)

how do I make the derivation 

  (1+0)*(2-x)+(x+4)*(0-1)

?

I dont understand how the derivation came about. Help is much appreciated.

Upvotes: 1

Views: 1331

Answers (1)

user502187
user502187

Reputation:

I guess by derivation you mean the mathematical derivative of the function f(x) = (x+4)*(2-x). This is a very famous old and not so hard computer algebra problem, solutions have been initially written for example in lisp.

A Prolog version is straight forward. You implement derivation rules such as:

d/dx (f + g) = d/dx f + d/dx g  
d/dx (f * g) = d/dx f * g + d/dx g * f
etc..

I suggest you give it first a try by yourself bevor you check for example deriv.p. A computer algebra based autodiff is here deriv.p.

Bye

Upvotes: 2

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