//this is very similar to parseFunctionParameters. Difference being in parseFunctionParameters, we expect the parameters to be
//identifiers wherease here when we are calling/invoking that function the arguments passed to those parameters can be Expressions such as
//(5, foobar, foobar+5)
private List <AST_Helper.Expression> parseExpressionList(TokenHelper.TokenType endToken)
{
List <AST_Helper.Expression> args = new List <AST_Helper.Expression>();
if (this.peekTokenIs(endToken))
{
this.nextToken();
return(args);
}
this.nextToken();
args.Add(this.parseExpression(Parser_Helper.precedence.LOWEST));
while (this.peekTokenIs(TokenHelper.TokenType.COMMA))
{
this.nextToken();
this.nextToken();
args.Add(this.parseExpression(Parser_Helper.precedence.LOWEST));
}
if (!this.expectPeek(endToken))
{
return(null);
}
return(args);
}
private bool expectPeek(TokenHelper.TokenType t) //if the expected token is present, this also advances the cursor to next token
{
if (this.peekTokenIs(t)) //and this should be reflected in the func name.
{
this.nextToken();
return(true);
}
else
{
this.peekError(t);
return(false);
}
}
public Token(TokenHelper.TokenType type, string literal)
{
Type = type; Literal = literal;
}
void registerInfix(TokenHelper.TokenType t, Parser_Helper.infixParseFn fn)
{
this.infixParseFns[t] = fn;
}
void registerPrefix(TokenHelper.TokenType t, Parser_Helper.prefixParserFn fn)
{
this.prefixParseFns[t] = fn;
}
void peekError(TokenHelper.TokenType t)
{
string message = string.Format("expected next token to be {0}, got {1} instead", t, this.peekToken.Type);
this.errors.Add(message);
}
private bool curTokenIs(TokenHelper.TokenType t)
{
return(this.curToken.Type == t);
}
private bool peekTokenIs(TokenHelper.TokenType t)
{
return(this.peekToken.Type == t);
}
private void noPrefixParseFnError(TokenHelper.TokenType type)
{
string message = string.Format("no prefix parse function for {0} found", type);
this.errors.Add(message);
}
public Token NextToken()
{
Token tok;
this.skipWhiteSpace();
switch (this.ch)
{
case '"':
tok = new Token(TokenHelper.TokenType.STRING, this.readString());
//even though we have already read the next char in readString, we still want to call readchar() again(below). Therefore, in this case, do not return here.
break;
case '=':
if (this.peekChar() == '=')
{
var temp_ch = this.ch;
this.readChar();
string literal = temp_ch.ToString() + this.ch.ToString();
tok = new Token(TokenHelper.TokenType.EQ, literal);
}
else
{
tok = new Token(TokenHelper.TokenType.ASSIGN, this.ch.ToString());
}
break;
case ';':
tok = new Token(TokenHelper.TokenType.SEMICOLON, this.ch.ToString());
break;
case ':':
tok = new Token(TokenHelper.TokenType.COLON, this.ch.ToString());
break;
case '(':
tok = new Token(TokenHelper.TokenType.LPAREN, this.ch.ToString());
break;
case ')':
tok = new Token(TokenHelper.TokenType.RPAREN, this.ch.ToString());
break;
case ',':
tok = new Token(TokenHelper.TokenType.COMMA, this.ch.ToString());
break;
case '+':
tok = new Token(TokenHelper.TokenType.PLUS, this.ch.ToString());
break;
case '{':
tok = new Token(TokenHelper.TokenType.LBRACE, this.ch.ToString());
break;
case '}':
tok = new Token(TokenHelper.TokenType.RBRACE, this.ch.ToString());
break;
case '[':
tok = new Token(TokenHelper.TokenType.LBRACKET, this.ch.ToString());
break;
case ']':
tok = new Token(TokenHelper.TokenType.RBRACKET, this.ch.ToString());
break;
case '-':
tok = new Token(TokenHelper.TokenType.MINUS, this.ch.ToString());
break;
case '!':
if (this.peekChar() == '=')
{
var temp_ch = this.ch;
this.readChar();
string literal = temp_ch.ToString() + this.ch.ToString();
tok = new Token(TokenHelper.TokenType.NOT_EQ, literal);
}
else
{
tok = new Token(TokenHelper.TokenType.BANG, this.ch.ToString());
}
break;
case '/':
tok = new Token(TokenHelper.TokenType.SLASH, this.ch.ToString());
break;
case '*':
tok = new Token(TokenHelper.TokenType.ASTERISK, this.ch.ToString());
break;
case '<':
tok = new Token(TokenHelper.TokenType.LT, this.ch.ToString());
break;
case '>':
tok = new Token(TokenHelper.TokenType.GT, this.ch.ToString());
break;
case '\0':
tok = new Token(TokenHelper.TokenType.EOF, this.ch.ToString()); //todo:??
break;
default:
if (this.isLetter(this.ch))
{
string literal = this.readIdentifier();
TokenHelper.TokenType type = TokenHelper.LookupIdent(literal);
tok = new Token(type, literal);
//we don't want to call readchar() again(below) as we have already read the next char in readIdentifier. Therefore return here.
return(tok);
}
else if (this.isDigit(this.ch))
{
string literal = this.readNumber();
TokenHelper.TokenType type = TokenHelper.TokenType.INT;
tok = new Token(type, literal);
//we don't want to call readchar() again(below) as we have already read the next char in readNumber. Therefore return here.
return(tok);
}
else
{
tok = new Token(TokenHelper.TokenType.ILLEGAL, this.ch.ToString());
}
break;
}
this.readChar();
return(tok);
}