Dabscm Library Reference

Overview

(scm match) is a pattern-matching library: match tests a value against a series of patterns and evaluates the body of the first that fits, binding pattern variables along the way. There are also match-lambda, match-let, and friends.

Common uses

(import (scm match))

(match 42
  (0 'zero)
  (x x))                        ;; => 42  (x binds the value)

(match '(1 2 3)
  ((a b c) (+ a b c)))          ;; => 6

(match (cons 1 2)
  ((x . y) (list y x)))         ;; => (2 1)

(match '(1 2 3)
  ((first . rest) rest))        ;; => (2 3)

Patterns include literals, the wildcard _, variables, and pair/list destructuring. match-lambda builds a procedure that matches its argument, and match-let / match-let* / match-letrec destructure in bindings.