/// <summary>
/// Check if parse point reach end point or not.
/// </summary>
/// <param name="statement">input</param>
/// <param name="data"></param>
/// <returns>true:reach end point , false:not reach end point.</returns>
private bool isExit(string statement , ParsedData data)
{
return statement.Length <= data.INDEX;
}
/// <summary>
///
/// </summary>
/// <param name="statement">input expression's statement</param>
/// <param name="data"></param>
/// <returns></returns>
private ParsedData factor(string statement, ParsedData data)
{
var token = statement.ElementAt(data.INDEX);
if(token == Token.Parenthesis.BEGIN )
{
data.INDEX++;
if(isExit(statement,data))
{
throw new SyntaxException("'('と')'の対応が合いません。",data.INDEX);
}
var rExpr = expr(statement, data);
if (isExit(statement, rExpr))
{
throw new SyntaxException(")の対応が合わず、終端に到達しました。",data.INDEX);
}
if (statement.ElementAt(rExpr.INDEX) != Token.Parenthesis.END)
{
throw new SyntaxException(")が合わない",data.INDEX);
}
rExpr.INDEX++;
return rExpr;
}
else
{
string strNumber = "";
if (isMinusSign(token))
{
data.INDEX = data.INDEX + 1;
token = statement.ElementAt(data.INDEX);
strNumber = Token.Num.MINUS.ToString();
}
// 数字が一文字以上連続している場合は、数字として認識する。
if (!isNumber(token))
throw new SyntaxException("????",data.INDEX);
strNumber += token.ToString();
var idxBegin = data.INDEX;
var idxEnd = idxBegin;
for (int idx = idxBegin + 1; idx < statement.Length; idx++ )
{
var numWrk = statement.ElementAt(idxEnd + 1);
if (!isNumber(numWrk))
break;
idxEnd++;
strNumber += numWrk.ToString();
}
try
{
var number = long.Parse(strNumber);
idxEnd++;
return new ParsedData(number, idxEnd, data.MESSAGE);
}
catch(OverflowException ex)
{
throw new ParseOverflowException(ex.Message, idxBegin, strNumber);
}
}
}
/// <summary>
///
/// </summary>
/// <param name="statement">input expression's statement</param>
/// <param name="data"></param>
/// <returns></returns>
private ParsedData expr(string statement , ParsedData data)
{
var rLeft = term(statement , data);
if (isExit(statement, rLeft))
{
return rLeft;
}
while (true)
{
var tokenCurrent = statement.ElementAt(rLeft.INDEX);
if (tokenCurrent == Token.Operator.ADD)
{
var rRight = term(statement, new ParsedData(rLeft.NUMBER, rLeft.INDEX + 1, rLeft.MESSAGE));
rLeft.INDEX = rRight.INDEX;
rLeft.NUMBER = rLeft.NUMBER + rRight.NUMBER;
}
else if (tokenCurrent == Token.Operator.SUB)
{
var rRight = term(statement, new ParsedData(rLeft.NUMBER, rLeft.INDEX + 1, rLeft.MESSAGE));
rLeft.INDEX = rRight.INDEX;
rLeft.NUMBER = rLeft.NUMBER - rRight.NUMBER;
}
else
{
break;
}
if (isExit(statement, rLeft))
break;
}
return rLeft;
}
/// <summary>
///
/// </summary>
/// <param name="statement">input expression's statement</param>
/// <param name="data"></param>
/// <returns></returns>
private ParsedData term(string statement, ParsedData data)
{
var rLeft = factor(statement, data);
if (isExit(statement, rLeft))
{
return rLeft;
}
while (true)
{
var token = statement.ElementAt(rLeft.INDEX);
if (token == Token.Operator.MUL)
{
var rRight = factor(statement, new ParsedData(rLeft.NUMBER, rLeft.INDEX + 1, rLeft.MESSAGE));
rLeft.INDEX = rRight.INDEX;
rLeft.NUMBER = rLeft.NUMBER * rRight.NUMBER;
}
else if (token == Token.Operator.DIV)
{
var rRight = factor(statement, new ParsedData(rLeft.NUMBER, rLeft.INDEX + 1, rLeft.MESSAGE));
rLeft.INDEX = rRight.INDEX;
rLeft.NUMBER = rLeft.NUMBER / rRight.NUMBER;
}
else
{
break;
}
if (isExit(statement, rLeft))
break;
}
return rLeft;
}
/// <summary>
/// 計算機の入力式を解析する実行部
/// </summary>
/// <param name="statement"></param>
/// <returns></returns>
private ParserResult parse_exec( string statement)
{
var data = new ParsedData(0, 0, "");
var result = expr(statement,data);
// Check Syntax Accept Condition
if (isExit(statement, result))
{
return new ParserResult(result.NUMBER, result.MESSAGE);
}
else
{
//statementの終端に達する前に解析終了しました。
//文法エラーが発生しています。
throw new SyntaxException(string.Format("{0}文字目近辺で異常終了しました。",result.INDEX),result.INDEX);
}
}
