public void ParseEngineLexemeShouldConsumeCharacterSequence()
{
ProductionExpression sequence = "sequence";
sequence.Rule = (Expr)'a' + 'b' + 'c' + '1' + '2' + '3';
var grammar = new GrammarExpression(sequence, new[] { sequence }).ToGrammar();
var lexerRule = new GrammarLexerRule(new TokenType("sequence"), grammar);
var lexeme = new ParseEngineLexeme(lexerRule);
var input = "abc123";
for (int i = 0; i < input.Length; i++)
Assert.IsTrue(lexeme.Scan(input[i]));
Assert.IsTrue(lexeme.IsAccepted());
}
public void ParseEngineLexemeShouldMatchLongestAcceptableTokenWhenGivenAmbiguity()
{
var lexemeList = new List<ParseEngineLexeme>();
ProductionExpression There = "there";
There.Rule = (Expr)'t' + 'h' + 'e' + 'r' + 'e';
var thereGrammar = new GrammarExpression(There, new[] { There })
.ToGrammar();
var thereLexerRule = new GrammarLexerRule(new TokenType(There.ProductionModel.LeftHandSide.NonTerminal.Value), thereGrammar);
var thereLexeme = new ParseEngineLexeme(thereLexerRule);
lexemeList.Add(thereLexeme);
ProductionExpression Therefore = "therefore";
Therefore.Rule = (Expr)'t' + 'h' + 'e' + 'r' + 'e' + 'f' + 'o' + 'r' + 'e';
var thereforeGrammar = new GrammarExpression(Therefore, new[] { Therefore })
.ToGrammar();
var thereforeLexerRule = new GrammarLexerRule(new TokenType(Therefore.ProductionModel.LeftHandSide.NonTerminal.Value), thereforeGrammar);
var thereforeLexeme = new ParseEngineLexeme(thereforeLexerRule);
lexemeList.Add(thereforeLexeme);
var input = "therefore";
var i = 0;
for (; i < input.Length; i++)
{
var passedLexemes = lexemeList
.Where(l => l.Scan(input[i]))
.ToList();
// all existing lexemes have failed
// fall back onto the lexemes that existed before
// we read this character
if (passedLexemes.Count() == 0)
break;
lexemeList = passedLexemes;
}
Assert.AreEqual(i, input.Length);
Assert.AreEqual(1, lexemeList.Count);
var remainingLexeme = lexemeList[0];
Assert.IsNotNull(remainingLexeme);
Assert.IsTrue(remainingLexeme.IsAccepted());
}
public void Test_Lexeme_That_Consumes_Whitespace()
{
var grammar = new GrammarBuilder("S")
.Production("S", r=>r
.Rule("W")
.Rule("W", "S"))
.Production("W", r => r
.Rule(new WhitespaceTerminal()))
.ToGrammar();
var lexerRule = new GrammarLexerRule(
"whitespace",
grammar);
var parseEngine = new ParseEngine(lexerRule.Grammar);
var lexeme = new ParseEngineLexeme(parseEngine, new TokenType("whitespace"));
var input = "\t\r\n\v\f ";
for (int i = 0; i < input.Length; i++)
Assert.IsTrue(lexeme.Scan(input[i]));
Assert.IsTrue(lexeme.IsAccepted());
}
public void ParseEngineLexemeShouldConsumeWhitespace()
{
ProductionExpression
S = "S",
W = "W";
S.Rule = W | W + S;
W.Rule = new WhitespaceTerminal();
var grammar = new GrammarExpression(S, new[] { S, W }).ToGrammar();
var lexerRule = new GrammarLexerRule(
"whitespace",
grammar);
var lexeme = new ParseEngineLexeme(lexerRule);
var input = "\t\r\n\v\f ";
for (int i = 0; i < input.Length; i++)
Assert.IsTrue(lexeme.Scan(input[i]), $"Unable to recognize input[{i}]");
Assert.IsTrue(lexeme.IsAccepted());
}
