Created
July 2, 2013 16:12
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This is an example of how Python's features get misused in ways that hint at symbolic programming in Lisp.
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| # In Python it is common (though probably inadvisable) to | |
| # use Exceptions for flow control in situations that are | |
| # really not that exceptional. The Exception classes | |
| # function as symbols for what is essentially symbolic | |
| # programming using the exception handling machinery | |
| # for the actual flow control. | |
| class ValidationError(Exception): | |
| pass | |
| class RouteNotFound(Exception): | |
| pass | |
| def handler(request): | |
| try: | |
| validate_request(request) | |
| except ValidationError: | |
| handle_validation_error(request) | |
| except RouteNotFound: | |
| handle_route_not_found(request) | |
| ;; in Common Lisp or similar you could do something like this | |
| ;; where the validate-request function just returns a symbol | |
| ;; instead of raising an exception, and normal case matching | |
| ;; on the symbol for flow control. | |
| (defun handler (request) | |
| (let ((result (validate-request request))) | |
| (case request | |
| (validation-error (handle-validation-error request)) | |
| (route-not-found (handle-route-not-found request))))) |
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