Functions: Using Patterns in Delayed Assignment (:=)

Defining Functions with Patterns

Defining functions with patterns probably combines the most useful aspects of Mathematica.  Define a function that takes patten matching x as its first argument and an argument matching n as its second argument and returns x to the power:

This works fine, but suppose we had defined  x ahead of time

RHS evaluated, it is x^(second argument) which is currently 4^(second argument)

Delayed Assignmet (:=)

The problem with the above functions is that the evaluation is made immediately.  For a function, the argument serves as a placeholder for a future calculation.  You do not wish to have the right–hand–side evaluated until the actual values of left–hand–side are specified.  The remedy is to use delayed assignment :=

Created by Wolfram Mathematica 6.0  (06 September 2007)