Case-lambda · Husk 3.2

(case-lambda {clause} ... ) case-lambda library syntax

Syntax: Each clause is of the form (formals body), where formals and body have the same syntax as in a lambda expression.

Semantics: A case-lambda expression evaluates to a procedure that accepts a variable number of arguments and is lexically scoped in the same manner as a procedure resulting from a lambda expression. When the procedure is called, the first clause for which the arguments agree with formals is selected, where agreement is specified as for the formals of a lambda expression. The variables of formals are bound to fresh locations, the values of the arguments are stored in those locations, the body is evaluated in the extended environment, and the results of body are returned as the results of the procedure call.

It is an error for the arguments not to agree with the formals of any clause.

(define range
  (case-lambda
    ((e) (range 0 e))
    ((b e) (do ((r '() (cons e r))
                (e (- e 1) (- e 1)))
             ((< e b) r)))))

(range 3) ==> (0 1 2)
(range 3 5) ==> (3 4)