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Pre- and postconditions made easy
This egg implements some routines, which are outsourced from simple-exceptions. In particular macros << and >>, which accept an argument or result, checks it against zero or more predicates and returns it in case of success unchanged. Otherwise it prints a meaningful error message, showing i.a. the offending predicate and the argument's or result's name. They are implemented as macros instead of procedures, because I didn't want an extra parameter with the argument's or result's name. In reimplementing those routines, I changed the syntax a bit, so be careful, if you used the eqally named routines from simple-expressions.
Interface
assert*
[syntax] (assert* loc xpr ....)checks the expressions xpr .... in sequence and raises an exception for the first failing expression with location property loc and arguments property the failing expression quoted.
<<<
[syntax] (<<< loc arg arg? ...)precondition test: returns arg unchanged only if all predicates arg? return #t on it, otherwise an error message with the offending predicate and the location loc is printed.
<<
[syntax] (<< arg arg? ...)precondition test: returns arg unchanged only if all predicates arg? return #t on it, otherwise an error message with the offending predicate is printed.
>>>
[syntax] (>>> loc result result? ...)postcondition test: returns result unchanged only if all predicates result? return #t on it, otherwise an error message with the offending predicate and the location loc is printed.
>>
[syntax] (>> result result? ...)postcondition test: passes result unchanged only if all predicates result? return #t on it otherwise an error message with the offending predicate is printed.
true?
[procedure] (true? xpr)returns always #t
false?
[procedure] (false? xpr)returns always #f
Examples
(define x 5)
(<< x positive? odd?)
- -> 5
(<< x zero? odd?)
- -> error
(<< x positive? even?)
- -> error
Last update
Jan 30, 2019
Author
License
Copyright (c) 2014-2019, Juergen Lorenz All rights reserved.
Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. Neither the name of the author nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
Version History
- 1.0
- extracted and modified from simple-exceptions