Case-Lambda Library

The (scheme case-lambda) library exports the case-lambda syntax.

For more information see the R⁷RS Scheme Specification.

• case-lambda

case-lambda

Syntax

(case-lambda {clause} ...)

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)