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using System;
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using System.Collections.Generic;
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using System.Text;
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public sealed class Parser
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{
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private int currentToken;
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private readonly Statement parsingOutput;
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private IList<object> listTokens;
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public Parser(IList<object> tokens)
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{
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listTokens = tokens;
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currentToken = 0;
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parsingOutput = ParseStatement();
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}
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public Statement GetParsedStatement
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{
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get { return parsingOutput; }
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}
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public void ExceptionHandler(string strException)
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{
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throw new Exception(strException);
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}
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private Statement ParseStatement()
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{
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Statement parsedStatement;
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if (currentToken == listTokens.Count)
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{
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ExceptionHandler("statement was expected before end of file");
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}
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if (listTokens[currentToken].Equals("print"))
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{
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currentToken++;
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Write _Write = new Write();
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_Write.Expression = ParseExpression();
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parsedStatement = _Write;
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}
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else if (listTokens[currentToken].Equals("var"))
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{
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currentToken++;
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DeclareVariable _DeclareVariable = new DeclareVariable();
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if (currentToken < listTokens.Count && listTokens[currentToken] is string)
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{
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_DeclareVariable.Identifier = (string)listTokens[currentToken];
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}
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else
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{
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ExceptionHandler("variable name was expected after 'var'");
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}
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currentToken++;
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if (currentToken == listTokens.Count || listTokens[currentToken].ToString() != Lexer.Tokens.EqualTo.ToString())
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{
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ExceptionHandler("= sign was expected after 'var identifier'");
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}
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currentToken++;
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_DeclareVariable.Expression = ParseExpression();
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parsedStatement = _DeclareVariable;
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}
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else if (listTokens[currentToken].Equals("call"))
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{
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currentToken++;
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CallFunction _CallFunction = new CallFunction();
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if (currentToken < listTokens.Count && listTokens[currentToken] is string)
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{
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_CallFunction.FunctionName = (string)listTokens[currentToken];
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}
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else
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{
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ExceptionHandler("function name is expected after 'call'");
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}
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currentToken++;
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_CallFunction.Parameter1 = ParseExpression();
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//index++;
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if (currentToken == listTokens.Count || listTokens[currentToken].ToString() != Lexer.Tokens.Comma.ToString())
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{
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ExceptionHandler("',' sign was expected after first parameter");
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}
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currentToken++;
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_CallFunction.Parameter2 = ParseExpression();
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//index++;
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if (currentToken == listTokens.Count || listTokens[currentToken].ToString() != Lexer.Tokens.Comma.ToString())
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{
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ExceptionHandler("',' sign was expected after second parameter");
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}
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currentToken++;
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_CallFunction.Parameter3 = ParseExpression();
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//index++;
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if (currentToken == listTokens.Count || listTokens[currentToken].ToString() != Lexer.Tokens.Terminator.ToString())
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{
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ExceptionHandler("';' sign was expected after third parameter");
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}
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parsedStatement = _CallFunction;
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}
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else if (listTokens[currentToken].Equals("string") || listTokens[currentToken].Equals("numeric") || listTokens[currentToken].Equals("void"))
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{
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DeclareFunction _DeclareFunction = new DeclareFunction();
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_DeclareFunction.ReturnType = listTokens[currentToken].ToString();
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currentToken++;
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if (currentToken < listTokens.Count && listTokens[currentToken] is string)
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{
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_DeclareFunction.FunctionName = (string)listTokens[currentToken];
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}
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else
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{
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ExceptionHandler("function name is expected after return type");
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}
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currentToken++;
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if (listTokens[currentToken].Equals("var"))
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{
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currentToken++;
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DeclareVariable _DeclareVariable = new DeclareVariable();
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if (currentToken < listTokens.Count && listTokens[currentToken] is string)
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{
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_DeclareVariable.Identifier = (string)listTokens[currentToken];
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}
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else
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{
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ExceptionHandler("variable name was expected after 'var'");
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}
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currentToken++;
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if (currentToken == listTokens.Count || listTokens[currentToken].ToString() != Lexer.Tokens.EqualTo.ToString())
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{
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ExceptionHandler("= sign was expected after 'var identifier'");
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}
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currentToken++;
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_DeclareVariable.Expression = ParseExpression();
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_DeclareFunction.Parameter1 = _DeclareVariable;
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}
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currentToken++;
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if (listTokens[currentToken].Equals("var"))
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{
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currentToken++;
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DeclareVariable _DeclareVariable = new DeclareVariable();
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if (currentToken < listTokens.Count && listTokens[currentToken] is string)
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{
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_DeclareVariable.Identifier = (string)listTokens[currentToken];
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}
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else
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{
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ExceptionHandler("variable name was expected after 'var'");
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}
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currentToken++;
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if (currentToken == listTokens.Count || listTokens[currentToken].ToString() != Lexer.Tokens.EqualTo.ToString())
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{
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ExceptionHandler("= sign was expected after 'var identifier'");
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}
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currentToken++;
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_DeclareVariable.Expression = ParseExpression();
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_DeclareFunction.Parameter2 = _DeclareVariable;
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}
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currentToken++;
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if (listTokens[currentToken].Equals("var"))
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{
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currentToken++;
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DeclareVariable _DeclareVariable = new DeclareVariable();
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if (currentToken < listTokens.Count && listTokens[currentToken] is string)
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{
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_DeclareVariable.Identifier = (string)listTokens[currentToken];
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}
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else
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{
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ExceptionHandler("variable name was expected after 'var'");
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}
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currentToken++;
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if (currentToken == listTokens.Count || listTokens[currentToken].ToString() != Lexer.Tokens.EqualTo.ToString())
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{
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ExceptionHandler("= sign was expected after 'var identifier'");
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}
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currentToken++;
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_DeclareVariable.Expression = ParseExpression();
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_DeclareFunction.Parameter3 = _DeclareVariable;
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}
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if (currentToken == listTokens.Count || !listTokens[currentToken].Equals("begin"))
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{
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ExceptionHandler("expected 'begin' after input parameters");
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}
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currentToken++;
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_DeclareFunction.Body = ParseStatement();
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parsedStatement = _DeclareFunction;
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if (currentToken == listTokens.Count || !listTokens[currentToken].Equals("endfunc"))
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{
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ExceptionHandler("unterminated function', 'endfunc' expected at the end");
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}
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currentToken++;
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}
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else if (listTokens[currentToken].Equals("read"))
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{
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currentToken++;
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ReadInput _ReadInput = new ReadInput();
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if (currentToken < listTokens.Count && listTokens[currentToken] is string)
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{
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_ReadInput.Identifier = (string)listTokens[currentToken++];
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parsedStatement = _ReadInput;
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}
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else
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{
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ExceptionHandler("variable name is expected after 'read'");
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parsedStatement = null;
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}
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}
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// IfThenElse ifThenElse = new IfThenElse();
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// RelationalExpression relExpr = new RelationalExpression();
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// relExpr.Left = ParseExpression();
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// if (listTokens[index] == Scanner.EqualTo)
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// relExpr.Operand = RelationalOperands.EqualTo;
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// else if (listTokens[index] == Scanner.LessThan)
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// relExpr.Operand = RelationalOperands.LessThan;
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// else if (listTokens[index] == Scanner.GreaterThan)
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// relExpr.Operand = RelationalOperands.GreaterThan;
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// else
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// {
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// ExceptionHandler("expected relational operand");
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// }
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// index++;
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// relExpr.Right = ParseExpression();
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// ifThenElse.If = relExpr;
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// index++;
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// ifThenElse.Then = ParseStatement();
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// parsedStatement = ifThenElse;
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// //index++;
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else if (listTokens[this.currentToken].Equals("while"))
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{
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currentToken++;
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While _while = new While();
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_while.LeftExpression = ParseExpression();
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if (listTokens[currentToken].ToString() == Lexer.Tokens.EqualTo.ToString())
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_while.Operand = RelationalOperands.EqualTo;
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else if (listTokens[currentToken].ToString() == Lexer.Tokens.LessThan.ToString())
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_while.Operand = RelationalOperands.LessThan;
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else if (listTokens[currentToken].ToString() == Lexer.Tokens.GreaterThan.ToString())
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_while.Operand = RelationalOperands.GreaterThan;
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currentToken++;
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_while.RightExpression = ParseExpression();
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if (currentToken == listTokens.Count || !listTokens[currentToken].Equals("do"))
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{
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ExceptionHandler("expected 'do' after while");
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}
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currentToken++;
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_while.Body = ParseStatement();
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parsedStatement = _while;
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if (currentToken == listTokens.Count || !listTokens[currentToken].Equals("endwhile"))
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{
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ExceptionHandler("unterminated 'while', endwhile expected at the end");
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}
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currentToken++;
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}
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else if (listTokens[this.currentToken].Equals("if"))
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{
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currentToken++;
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IfThen _IfThen = new IfThen();
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_IfThen.LeftExpression = ParseExpression();
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if (listTokens[currentToken].ToString() == Lexer.Tokens.EqualTo.ToString())
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_IfThen.Operand = RelationalOperands.EqualTo;
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else if (listTokens[currentToken].ToString() == Lexer.Tokens.LessThan.ToString())
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_IfThen.Operand = RelationalOperands.LessThan;
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else if (listTokens[currentToken].ToString() == Lexer.Tokens.GreaterThan.ToString())
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_IfThen.Operand = RelationalOperands.GreaterThan;
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currentToken++;
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_IfThen.RightExpression = ParseExpression();
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if (currentToken == listTokens.Count || !listTokens[currentToken].Equals("then"))
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{
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ExceptionHandler("expected 'then' after if");
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}
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currentToken++;
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_IfThen.ThenBody = ParseStatement();
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if (currentToken == listTokens.Count || !listTokens[currentToken].Equals("else"))
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{
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ExceptionHandler("'else' is expected");
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}
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currentToken++;
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_IfThen.ElseBody = ParseStatement();
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parsedStatement = _IfThen;
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if (currentToken == listTokens.Count || !listTokens[currentToken].Equals("endif"))
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{
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ExceptionHandler("unterminated 'if', endif expected at the end");
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}
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currentToken++;
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}
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else if (listTokens[currentToken].Equals("for"))
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{
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currentToken++;
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For _For = new For();
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if (currentToken < listTokens.Count && listTokens[currentToken] is string)
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{
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_For.Identifier = (string)listTokens[currentToken];
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}
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else
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{
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ExceptionHandler("expected identifier after 'for'");
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}
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currentToken++;
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if (currentToken == listTokens.Count || listTokens[currentToken].ToString() != Lexer.Tokens.EqualTo.ToString())
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{
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ExceptionHandler("for missing '='");
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}
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currentToken++;
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_For.From = ParseExpression();
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if (currentToken == listTokens.Count || !listTokens[currentToken].Equals("to"))
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{
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ExceptionHandler("expected 'to' after for");
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}
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currentToken++;
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_For.To = ParseExpression();
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if (currentToken == listTokens.Count || !listTokens[currentToken].Equals("do"))
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{
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ExceptionHandler("expected 'do' after from expression in for loop");
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}
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currentToken++;
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_For.Body = ParseStatement();
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parsedStatement = _For;
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if (currentToken == listTokens.Count || !listTokens[currentToken].Equals("end"))
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{
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ExceptionHandler("unterminated 'for' loop body");
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}
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currentToken++;
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}
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else if (listTokens[currentToken] is string)
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{
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// assignment
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Assignment _Assignment = new Assignment();
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_Assignment.Identifier = (string)listTokens[currentToken++];
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if (currentToken == listTokens.Count || listTokens[currentToken].ToString() != Lexer.Tokens.EqualTo.ToString())
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{
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ExceptionHandler("expected '='");
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}
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currentToken++;
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_Assignment.Expression = ParseExpression();
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parsedStatement = _Assignment;
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}
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else
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{
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ExceptionHandler("parse error at token " + currentToken + ": " + listTokens[currentToken]);
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parsedStatement = null;
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}
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if (currentToken < listTokens.Count && listTokens[currentToken].ToString() == Lexer.Tokens.Terminator.ToString())
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{
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currentToken++;
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if (currentToken < listTokens.Count && !listTokens[currentToken].Equals("end")
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&& !listTokens[currentToken].Equals("else") && !listTokens[currentToken].Equals("endif")
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&& !listTokens[currentToken].Equals("endwhile") && !listTokens[currentToken].Equals("endfunc"))
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{
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StatementSequence sequence = new StatementSequence();
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sequence.Left = parsedStatement;
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sequence.Right = ParseStatement();
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parsedStatement = sequence;
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}
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}
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return parsedStatement;
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}
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455 |
private Expression ParseExpression()
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456 |
{
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457 |
Expression parsedExpression;
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458 |
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459 |
if (currentToken == listTokens.Count)
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460 |
{
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461 |
ExceptionHandler("expected expression, got EOF");
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}
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463 |
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464 |
if (listTokens[currentToken] is StringBuilder)
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465 |
{
|
|
466 |
string value = ((StringBuilder)listTokens[currentToken++]).ToString();
|
|
467 |
AlphaNumericValue _AlphaNumericValue = new AlphaNumericValue();
|
|
468 |
_AlphaNumericValue.Value = value;
|
|
469 |
parsedExpression = _AlphaNumericValue;
|
|
470 |
}
|
|
471 |
else if (listTokens[currentToken] is int)
|
|
472 |
{
|
|
473 |
int intValue = (int)listTokens[currentToken++];
|
|
474 |
NumericValue _NumericValue = new NumericValue();
|
|
475 |
_NumericValue.Value = intValue;
|
|
476 |
parsedExpression = _NumericValue;
|
|
477 |
}
|
|
478 |
else if (listTokens[currentToken] is string)
|
|
479 |
{
|
|
480 |
string identifier = (string)listTokens[currentToken++];
|
|
481 |
Identifier _Identifier = new Identifier();
|
|
482 |
_Identifier.IdentifierName = identifier;
|
|
483 |
parsedExpression = _Identifier;
|
|
484 |
}
|
|
485 |
else
|
|
486 |
{
|
|
487 |
ExceptionHandler("expected string literal, int literal, or variable");
|
|
488 |
return null;
|
|
489 |
}
|
|
490 |
|
|
491 |
//if (index < listTokens.Count && listTokens[index] != Scanner.Terminator && listTokens[index].GetType() != typeof(StringBuilder))
|
|
492 |
if (listTokens[currentToken].ToString() != Lexer.Tokens.Terminator.ToString())
|
|
493 |
{
|
|
494 |
if (listTokens[currentToken].ToString() == Lexer.Tokens.Add.ToString() || listTokens[currentToken].ToString() == Lexer.Tokens.Subtract.ToString()
|
|
495 |
|| listTokens[currentToken].ToString() == Lexer.Tokens.Multiply.ToString() || listTokens[currentToken].ToString() == Lexer.Tokens.Divide.ToString())
|
|
496 |
{
|
|
497 |
ArithmaticExpression arithmaticExpression = new ArithmaticExpression();
|
|
498 |
arithmaticExpression.Left = parsedExpression;
|
|
499 |
if (listTokens[currentToken].ToString() == Lexer.Tokens.Add.ToString())
|
|
500 |
arithmaticExpression.Operand = ArithmaticOperands.Add;
|
|
501 |
else if (listTokens[currentToken].ToString() == Lexer.Tokens.Subtract.ToString())
|
|
502 |
arithmaticExpression.Operand = ArithmaticOperands.Subtract;
|
|
503 |
else if (listTokens[currentToken].ToString() == Lexer.Tokens.Multiply.ToString())
|
|
504 |
arithmaticExpression.Operand = ArithmaticOperands.Multiply;
|
|
505 |
else if (listTokens[currentToken].ToString() == Lexer.Tokens.Divide.ToString())
|
|
506 |
arithmaticExpression.Operand = ArithmaticOperands.Division;
|
|
507 |
currentToken++;
|
|
508 |
|
|
509 |
arithmaticExpression.Right = ParseExpression();
|
|
510 |
parsedExpression = arithmaticExpression;
|
|
511 |
}
|
|
512 |
}
|
|
513 |
return parsedExpression;
|
|
514 |
}
|
|
515 |
}
|