link usage
July 19, 1991; Ralph E. Griswold
This file is in the public domain.
These procedures provide various common services:
Usage(s) stops executions with a message concerning the
expected form of usage of a program.
Error(L[]) writes arguments to &errout and returns.
ErrorCheck(l,f) reports an error that has been converted to
failure.
Feature(s) succeeds if feature s is available in the running
implementation of Icon.
Requires(s) terminates execution is feature s is not available.
Signature() writes the version, host, and features support in
the running implementation of Icon.