Convenience forms for working with parameters.
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 exn:fail:contract 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has been superseded by the parameter/c contract in PLT 4.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
|> (with-foo 10 (foo))|
|> (with-foo "bar" 10)|
Expected (U integer #f), received "bar"