java - Parsing negative numbers with jparsec -

java - Parsing negative numbers with jparsec -

using jparsec, i'm trying parse numbers may or may not negative:

@test public void canparseintegervalues() { assertequals(0, valueparser.parser.parse("0")); assertequals(276, valueparser.parser.parse("276")); assertequals(-3874, valueparser.parser.parse("-3874")); }

i've not been able figure out how declare parser. i've tried:

private static final parser<integer> integer_value_parser = terminals.integerliteral.tokenizer .map(new map<fragment, integer>() { @override public integer map(fragment from) { homecoming integer.valueof(from.text()); } });

this doesn't work because terminals.integerliteral.tokenizer not accommodate minus sign. next, tried:

private static final parser<integer> integer_value_parser = parsers.sequence( scanners.string("-").optional().token(), terminals.integerliteral.tokenizer .map(new map<fragment, integer>() { @override public integer map(fragment from) { homecoming integer.valueof(from.text()); } }));

this doesn't work because negative sign discarded , map function never sees it.

can tell me how correctly parse integers may or may not positive using jparsec?

edit: found way it, find hard believe best way:

private static final parser<integer> integer_value_parser = parsers.sequence( scanners.string("-").many(), terminals.integerliteral.tokenizer, new map2<list<void>, fragment, integer>() { @override public integer map(list<void> from1, fragment from2) { boolean isnegative = (from1.size() % 2) == 1; if (isnegative) { homecoming -1 * integer.valueof(from2.text()); } else { homecoming integer.valueof(from2.text()); } } });

you can have @ calculator class in jparsec's examples: https://github.com/abailly/jparsec/blob/master/jparsec-examples/src/main/java/org/codehaus/jparsec/examples/calculator/calculator.java here negative integers handled integers on prefix - operator has been applied.

alternatively can declare pattern comprising minus sign:

public void test() { pattern regex = patterns.regex("-?\\d+"); parser<integer> integer = scanners.pattern(regex, "integer").source().map(new map<string, integer>() { @override public integer map(string s) { homecoming integer.parseint(s); } }); assertequals(-42, (int) integer.parse("-42")); }

hth

arnaud

java parsing jparsec