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Static typable EP solution
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| (defpackage :fwoar.extend | |
| (:use :cl ) | |
| (:export )) | |
| (in-package :fwoar.extend) | |
| #| ------------- Begin Library ------------- |# | |
| (defclass animal () | |
| ()) | |
| (defclass operation () | |
| ()) | |
| (defgeneric operate (animal operation) | |
| #| This method ensures type safety: as long as we're given something in the domain of the function | |
| (animal, operation) => effect}, we'll get a result. |# | |
| (:method ((animal animal) (operation operation)) | |
| (format *standard-output* "the animal is unresponsive~%"))) | |
| (defclass turtle (animal) | |
| ()) | |
| #| -------------- End Library -------------- |# | |
| (defclass cat (animal) | |
| (#| cat-specific members here |#)) | |
| (defclass dog (animal) | |
| (#| dog-specific members here |#)) | |
| (defclass greet (operation) | |
| ()) | |
| (defclass leave (operation) | |
| ()) | |
| (defmethod operate ((animal cat) (operation greet)) | |
| (format *standard-output* "the cat stands aloof~%")) | |
| (defmethod operate ((animal cat) (operation leave)) | |
| (format *standard-output* "the cat purs happily~%")) | |
| (defmethod operate ((animal dog) (operation greet)) | |
| (format *standard-output* "the dog wags its tail joyfully~%")) | |
| (defmethod operate ((animal dog) (operation leave)) | |
| (format *standard-output* "the dog looks very sad~%")) | |
| (defun main () | |
| (dolist (animal (list (make-instance 'cat) | |
| (make-instance 'dog) | |
| (make-instance 'turtle))) | |
| (dolist (action (list (make-instance 'greet) | |
| (make-instance 'leave))) | |
| (visit animal action)))) #| ===> | |
| FWOAR.EXTEND> (main) | |
| the cat stands aloof | |
| the cat purs happily | |
| the dog wags its tail joyfully | |
| the dog looks very sad | |
| the animal is unresponsive | |
| the animal is unresponsive | |
| |# |
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