Examples of org.jnode.shell.syntax.MuParser$ChoicePoint

org.jnode.shell.syntax.MuParser
This class implements parsing of a token stream against a MuSyntax graph. The parser binds token values against Argument instances as it goes, and does full backtracking when it reaches a point where it cannot make forward progress. The backtracking mechanism manages the parser state and also records the Arguments that have been 'set', and therefore need to be 'unset' when we backtrack.
When we are doing a normal parse, the various alternatives in the MuSyntax graph are explored until either there is a successful parse (consuming all tokens), or we run out of alternatives. The latter case results in an exception and a failed parse.
When we are doing a completion parse, all alternatives are explored irrespective of parse success.
A MuSyntax may contain "infinite" loops, or other pathologies that trigger excessive backtracking. To avoid problems, the 'parse' method takes a 'stepLimit' parameter that causes the parse to fail if it has not terminated soon enough.
The MuParser uses the SharedStack class to record syntax stacks for backtracking. This is a special purpose Deque that avoids unnecessary copying of the stack state. If you suspect that this is causing problems, replace {@code new SharedStack(...)}with {@code new LinkedList(...)}. @author crawley@jnode.org

        FileArgument fileArg = new FileArgument("fileArg", Argument.MULTIPLE);
        ArgumentBundle bundle = new ArgumentBundle(intArg, fileArg);


        // <start> :: = <<intArg>> | <<fileArg>>
        MuSyntax syntax = new MuAlternation(new MuArgument("intArg"), new MuArgument("fileArg"));
        MuParser parser = new MuParser();
        CommandLine cl;


        cl = new CommandLine(new String[] {"1"});
        parser.parse(syntax, null, cl.tokenIterator(), bundle);
        Assert.assertEquals(new Integer(1), intArg.getValue());
        Assert.assertEquals(false, fileArg.isSet());


        cl = new CommandLine(new String[] {"x"});
        parser.parse(syntax, null, cl.tokenIterator(), bundle);
        Assert.assertEquals(new File("x"), fileArg.getValue());
        Assert.assertEquals(false, intArg.isSet());


    }

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        MuSyntax syntax =
                new MuAlternation("root", new MuArgument("fileArg"), new MuSequence(new MuArgument(
                        "intArg"), new MuBackReference("root")));
        syntax.resolveBackReferences();


        MuParser parser = new MuParser();
        CommandLine cl;


        cl = new CommandLine(new String[] {"x"});
        parser.parse(syntax, null, cl.tokenIterator(), bundle);
        Assert.assertEquals(1, fileArg.getValues().length);
        Assert.assertEquals(0, intArg.getValues().length);


        cl = new CommandLine(new String[] {"1", "x"});
        parser.parse(syntax, null, cl.tokenIterator(), bundle);
        Assert.assertEquals(1, fileArg.getValues().length);
        Assert.assertEquals(1, intArg.getValues().length);


        cl = new CommandLine(new String[] {"1", "2", "x"});
        parser.parse(syntax, null, cl.tokenIterator(), bundle);
        Assert.assertEquals(1, fileArg.getValues().length);
        Assert.assertEquals(2, intArg.getValues().length);


        try {
            cl = new CommandLine(new String[] {"1", "2", ""});
            parser.parse(syntax, null, cl.tokenIterator(), bundle);
            Assert.fail("expected SEE");
        } catch (CommandSyntaxException ex) {
            // expected
        }
    }

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        // <root> ::= ( <<intArg>> <root> ) | <<fileArg>>
        MuSyntax syntax =
                new MuAlternation("root", new MuSequence(new MuArgument("intArg"),
                        new MuBackReference("root")), new MuArgument("fileArg"));
        syntax.resolveBackReferences();
        MuParser parser = new MuParser();
        CommandLine cl;


        cl = new CommandLine(new String[] {"x"});
        parser.parse(syntax, null, cl.tokenIterator(), bundle);
        Assert.assertEquals(1, fileArg.getValues().length);
        Assert.assertEquals(0, intArg.getValues().length);


        cl = new CommandLine(new String[] {"1", "x"});
        parser.parse(syntax, null, cl.tokenIterator(), bundle);
        Assert.assertEquals(1, fileArg.getValues().length);
        Assert.assertEquals(1, intArg.getValues().length);


        cl = new CommandLine(new String[] {"1", "1", "x"});
        parser.parse(syntax, null, cl.tokenIterator(), bundle);
        Assert.assertEquals(1, fileArg.getValues().length);
        Assert.assertEquals(2, intArg.getValues().length);


        try {
            cl = new CommandLine(new String[] {"1", "1", ""});
            parser.parse(syntax, null, cl.tokenIterator(), bundle);
            Assert.fail("expected SEE");
        } catch (CommandSyntaxException ex) {
            // expected
        }
    }

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            new MuBackReference("root")), new MuSequence(new MuArgument("bigArg"), new MuArgument("smallArg"))),
            new MuAlternation(new MuSequence(new MuArgument("intArg"), new MuBackReference("root")),
                new MuArgument("bigArg")));
        syntax.resolveBackReferences();


        MuParser parser = new MuParser();
        CommandLine cl;


        cl = new CommandLine(new String[] {"BIG"});
        parser.parse(syntax, null, cl.tokenIterator(), bundle);
        Assert.assertEquals(1, bigArg.getValues().length);
        Assert.assertEquals(0, smallArg.getValues().length);
        Assert.assertEquals(0, intArg.getValues().length);


        cl = new CommandLine(new String[] {"1", "LARGE"});
        parser.parse(syntax, null, cl.tokenIterator(), bundle);
        Assert.assertEquals(1, bigArg.getValues().length);
        Assert.assertEquals(0, smallArg.getValues().length);
        Assert.assertEquals(1, intArg.getValues().length);


        cl = new CommandLine(new String[] {"1", "2", "BIG"});
        parser.parse(syntax, null, cl.tokenIterator(), bundle);
        Assert.assertEquals(1, bigArg.getValues().length);
        Assert.assertEquals(0, smallArg.getValues().length);
        Assert.assertEquals(2, intArg.getValues().length);


        cl = new CommandLine(new String[] {"1", "2", "3", "BIG", "SMALL"});
        parser.parse(syntax, null, cl.tokenIterator(), bundle);
        Assert.assertEquals(1, bigArg.getValues().length);
        Assert.assertEquals(1, smallArg.getValues().length);
        Assert.assertEquals(3, intArg.getValues().length);


        try {
            cl = new CommandLine(new String[] {"1", "2", "TINY"});
            parser.parse(syntax, null, cl.tokenIterator(), bundle);
            Assert.fail("expected SEE");
        } catch (CommandSyntaxException ex) {
            // expected
        }
    }

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Related Classes of org.jnode.shell.syntax.MuParser$ChoicePoint

org.jnode.shell.syntax.CommandSyntaxException.Context

org.jnode.test.shell.syntax.MuParserTest

org.jnode.test.shell.syntax.MuParserTest2

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