|(require ( untyped/unlib/parameter))|
Convenience forms for working with parameters.
|( pred type-message) → (any -> any)|
|pred : (any -> )|
Creates a procedure that may be used as a parameter’s guard procedure. The guard only allows values for which pred returns #t. If an invalid value is supplied, the guard raises with an error message based on the supplied type-message.
has been superseded by the parameter/c contract in PLT 4.
|> (param 1)|
|> (param #f)|
|> (param #t)|
Expected (U integer #f), received #t
|( id initial-value guard-proc with-form-id)|
Convenience form that expands into two definitions:
id is bound to a parameter with the supplied initial-value and guard-proc;
with-form-id is bound to a syntax of the form:
(with-form-id expr body )
that expands to:
( ([id expr]) body )
|> (with-foo 10 (foo))|
|> (with-foo "bar" 10)|
Expected (U integer #f), received "bar"