cs381k p. 84

Pattern Matching

Given a pattern and an input, matching must:

Test whether the input matches the pattern. A common convention is to let pattern variables begin with `` ?''.
Keep variable bindings: for each pattern variable, the corresponding input.

Consider the example:


Pattern:      (- ?x (- ?y))

Input:        (- (sin theta) (- w))

The input matches the pattern; the bindings should be:


 ( (?x . (sin theta))
   (?y . w) )

This format is called an association list, or alist. The form ( x . y) , called a dotted pair, is produced by (cons x y) .