14.5 Whole-module Signatures and Units
In programs that use units, modules like "toy-factory-sig.rkt" and "simple-factory-unit.rkt" are common. The racket/signature and racket/unit module names can be used as languages to avoid much of the boilerplate module, signature, and unit declaration text.
For example, "toy-factory-sig.rkt" can be written as
|build-toys ; (integer? -> (listof toy?))|
|repaint ; (toy? symbol? -> toy?)|
|toy? ; (any/c -> boolean?)|
|toy-color ; (toy? -> symbol?)|
The signature toy-factory^ is automatically provided from the module, inferred from the filename "toy-factory-sig.rkt" by replacing the "-sig.rkt" suffix with ^.
Similarly, "simple-factory-unit.rkt" module can be written
|(printf "Factory started.\n")|
|(define-struct toy (color) #:transparent)|
|(define (build-toys n)|
|(for/list ([i (in-range n)])|
|(define (repaint t col)|
The unit simple-factory@ is automatically provided from the module, inferred from the filename "simple-factory-unit.rkt" by replacing the "-unit.rkt" suffix with @.