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Datei: MMParser.vdmsl Sprache: VDM

Original von: VDM^©

module MMParser
/***
MMParser
Author: Tomohiro Oda
Version: 0.01
License: the MIT License

Copyright (c) 2013 Tomohiro Oda and Software Research Associates, Inc.

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
***/
imports from VCParser all
exports functions eval : seq of char -> [int];
definitions
types
     TREE = VCParser`TREE;

values
     series = VCParser`series;
     either = VCParser`either;
     star = VCParser`star;
     trimBlanks = VCParser`trimBlanks;
     integer = VCParser`integer;
     takeChar = VCParser`takeChar;
     transtree = VCParser`transtree;
     parseInt = trimBlanks(integer);
     parseMul = series([takeChar('*'), parseInt]);
     parseDiv = series([takeChar('/'), parseInt]);
     parseTerm =
        transtree(
            liftOperator, series([parseInt, star(either([parseMul, parseDiv]))]));
     parseAdd = series([takeChar('+'), parseTerm]);
     parseSub = series([takeChar('-'), parseTerm]);
     parseExpression =
        transtree(
            liftOperator, series([parseTerm, star(either([parseAdd, parseSub]))]));

functions
    liftOperator : VCParser`TREE -> VCParser`TREE
    liftOperator(tree) ==
        let mk_VCParser`TREE(-, [left, right]) = tree
        in
            let mk_VCParser`TREE(-, rights) = right
            in
                cases rights:
                    [] -> left,
                    [mk_VCParser`TREE(-, [mk_VCParser`TREE(-, operator), operand])] ^ rest ->
                        liftOperator(
                            mk_VCParser`TREE(
                                nil,
                                [mk_VCParser`TREE(operator, [left, operand]),
                                mk_VCParser`TREE(nil, rest)]))
                    end;

    evalInt : seq of char -> int
    evalInt(string) ==
        cases string:
            "-" ^ rest -> evalInt(rest) * -1,
            [] -> 0,
            others ->
                evalInt([string(i) | i in set {1, ..., len string - 1}]) * 10
                + {'0' |-> 0, '1' |-> 1, '2' |-> 2, '3' |-> 3, '4' |-> 4, '5' |-> 5,
                '6' |-> 6, '7' |-> 7, '8' |-> 8, '9' |-> 9}(
                    string(len string))
            end
    measure lenChar;

    lenChar : seq of char -> nat
    lenChar(x) == len x;

    evalTree : TREE -> int
    evalTree(tree) ==
        cases tree:
            mk_VCParser`TREE("int", contents) -> evalInt(contents),
            mk_VCParser`TREE(nil, contents) -> evalInt(contents),
            mk_VCParser`TREE("*", [e1, e2]) -> evalTree(e1) * evalTree(e2),
            mk_VCParser`TREE("/", [e1, e2]) -> evalTree(e1) div evalTree(e2),
            mk_VCParser`TREE("+", [e1, e2]) -> evalTree(e1) + evalTree(e2),
            mk_VCParser`TREE("-", [e1, e2]) -> evalTree(e1) - evalTree(e2)
            end;

    hasDivZero : VCParser`TREE -> bool
    hasDivZero(tree) == cases tree:
        mk_VCParser`TREE("/", [-, mk_VCParser`TREE("int", "0")]) -> true,
        mk_VCParser`TREE("/", [-, mk_VCParser`TREE("int", "-0")]) -> true,
        mk_VCParser`TREE("int", -),
        mk_VCParser`TREE(nil, -) -> false,
        mk_VCParser`TREE(-, [tree1, tree2]) -> hasDivZero(tree1) or hasDivZero(tree2)
        end;

    eval : seq of char -> [int]
    eval(string) ==
        cases parseExpression(string):
            mk_VCParser`PARSED(tree, []) -> if hasDivZero(tree) then nil else evalTree(tree),
            others -> nil
            end;

end MMParser

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