private void LexChar(char characterToMatch, Token context)
{
int characterInt = PeekChar();
if (characterInt == -1)
{
return;
}
char character = (char)characterInt;
if (character != characterToMatch)
{
throw UnexpectedCharException.Create(character, context, characterToMatch);
}
AdvanceChar();
}
public Lexeme <Token> LexOne()
{
int characterInt;
char character;
Start:
do
{
characterInt = AdvanceChar();
if (characterInt == -1)
{
return(MakeLexeme(Token.EoF));
}
character = (char)characterInt;
}while (char.IsWhiteSpace(character));
if (character == '/' && PeekChar() == '/')
{
characterInt = AdvanceChar();
while (characterInt != -1 && characterInt != '\n')
{
characterInt = AdvanceChar();
}
if (characterInt == -1)
{
return(MakeLexeme(Token.EoF));
}
goto Start;
}
TokenBuffer.Append(character);
switch (character)
{
case '+':
return(MakeLexeme(SwitchOnNextCharacter(
Token.Add,
('+', Token.Increment),
('=', Token.AddCompoundAssign))));
case '-':
return(MakeLexeme(SwitchOnNextCharacter(
Token.Subtract,
('-', Token.Decrement),
('=', Token.SubtractCompoundAssign))));
case '*':
return(MakeLexeme(SwitchOnNextCharacter(
Token.Multiply,
('=', Token.MultiplyCompoundAssign))));
case '/':
return(MakeLexeme(SwitchOnNextCharacter(
Token.Divide,
('=', Token.DivideCompoundAssign))));
case '%':
return(MakeLexeme(SwitchOnNextCharacter(
Token.Remainder,
('=', Token.RemainderCompoundAssign))));
case '!':
return(MakeLexeme(
SwitchOnNextCharacter(Token.LogicalNot,
('=', Token.ComparisonNotEqual))));
case '~':
return(MakeLexeme(
Token.BitwiseNot));
case '^':
return(MakeLexeme(SwitchOnNextCharacter(
Token.BitwiseXor,
('=', Token.BitwiseXorCompoundAssign))));
case '=':
return(MakeLexeme(SwitchOnNextCharacter(
Token.Assign,
('=', Token.ComparisonEqual),
('>', Token.Arrow))));
case ':':
return(MakeLexeme(SwitchOnNextCharacter(
Token.Colon,
(':', Token.StaticAccessor))));
case '&':
var andType = SwitchOnNextCharacter(
Token.BitwiseAnd,
('=', Token.BitwiseAndCompoundAssign),
('&', Token.LogicalAnd));
if (andType == Token.LogicalAnd)
{
andType = SwitchOnNextCharacter(
Token.LogicalAnd,
('=', Token.LogicalAndCompoundAssign));
}
return(MakeLexeme(andType));
case '|':
var orType = SwitchOnNextCharacter(
Token.BitwiseOr,
('=', Token.BitwiseOrCompoundAssign),
('|', Token.LogicalOr));
if (orType == Token.LogicalOr)
{
orType = SwitchOnNextCharacter(
Token.LogicalOr,
('=', Token.LogicalOrCompoundAssign));
}
return(MakeLexeme(orType));
case '<':
var lessType = SwitchOnNextCharacter(
Token.ComparisonLessThan,
('=', Token.ComparisonLessThanOrEqual),
('-', Token.ReferenceAssign),
('<', Token.BitshiftLeft));
if (lessType == Token.BitshiftLeft)
{
lessType = SwitchOnNextCharacter(
Token.BitshiftLeft,
('=', Token.BitshiftLeftCompoundAssign));
}
return(MakeLexeme(lessType));
case '>':
var greaterType = SwitchOnNextCharacter(
Token.ComparisonGreaterThan,
('=', Token.ComparisonGreaterThanOrEqual),
('>', Token.BitshiftRight));
if (greaterType == Token.BitshiftRight)
{
greaterType = SwitchOnNextCharacter(
Token.BitshiftRight,
('=', Token.BitshiftRightCompoundAssign));
}
return(MakeLexeme(greaterType));
case '\'':
LexEscapableChar(Token.CharacterLiteral);
LexChar('\'', Token.CharacterLiteral);
return(MakeLexeme(Token.CharacterLiteral));
case '\"':
while (true)
{
int nextCharacterInt = PeekChar();
if (nextCharacterInt == -1)
{
throw UnexpectedCharException.Create(null, Token.StringLiteral, "a char or a string delimiter");
}
char nextCharacter = (char)nextCharacterInt;
if (nextCharacter == '\"')
{
AdvanceChar();
TokenBuffer.Append(nextCharacter);
break;
}
LexEscapableChar(Token.StringLiteral);
}
return(MakeLexeme(Token.StringLiteral));
case '{':
return(MakeLexeme(Token.LBraces));
case '}':
return(MakeLexeme(Token.RBraces));
case '[':
return(MakeLexeme(Token.LBrackets));
case ']':
return(MakeLexeme(Token.RBrackets));
case '(':
return(MakeLexeme(Token.LParens));
case ')':
return(MakeLexeme(Token.RParens));
case ';':
return(MakeLexeme(Token.Semicolon));
case '?':
return(MakeLexeme(Token.QuestionMark));
case ',':
return(MakeLexeme(Token.Comma));
}
// Identifier or keyword
if (char.IsLetter(character) || character == '_')
{
while (true)
{
int nextCharacterInt = PeekChar();
if (nextCharacterInt == -1)
{
break;
}
char nextCharacter = (char)nextCharacterInt;
if (!char.IsLetterOrDigit(nextCharacter) && nextCharacter != '_')
{
break;
}
AdvanceChar();
TokenBuffer.Append(nextCharacter);
}
return(MakeLexeme(_keywords.TryGetValue(TokenBuffer.ToString(), out Token keyword) ? keyword : Token.Identifier));
}
// Numerical literal
{
bool reachedDot = false;
if (character == '.')
{
reachedDot = true;
int nextCharacterInt = PeekChar();
if (nextCharacterInt == -1)
{
throw UnexpectedCharException.Create(null, Token.FloatLiteral, "Digit");
}
character = (char)nextCharacterInt;
if (!char.IsDigit(character))
{
return(MakeLexeme(Token.Accessor));
//throw UnexpectedCharException.Create(character, Token.FloatLiteral, "Digit");
}
}
if (char.IsDigit(character))
{
LexNumber(ref reachedDot);
return(reachedDot
? MakeLexeme(Token.FloatLiteral)
: MakeLexeme(Token.IntegerLiteral));
}
}
throw UnexpectedCharException.Create(character, Token.EoF, "EoF");
}
