commonlisptokenizer.java

计算机代数系统

package net.sf.yacas;


class CommonLispTokenizer extends LispTokenizer
{
    String NextToken(LispInput aInput, LispHashTable aHashTable)
	{
		char c;
		int firstpos;

REDO://TODO FIXME
		firstpos = aInput.Position();

		// End of stream: return empty string
		if (aInput.EndOfStream())
			goto FINISH;

		c = aInput.Next();
		//printf("%c",c);

		//Parse brackets
		if (c == '(')      {}
		else if (c == ')') {}
		else if (c == '{') {}
		else if (c == '}') {}
		else if (c == '[') {}
		else if (c == ']') {}
		else if (c == ',') {}
		else if (c == '\'') {}
		else if (c == '%') {}
	//    else if (c == '\'') {}
		else if (c == '.' && !IsDigit(aInput.Peek()) )
		{
			while (aInput.Peek() == '.')
			{
				aInput.Next();
			}
		}
		// parse comments
		else if (c == '/' && aInput.Peek() == '*')
		{
			aInput.Next(); //consume *
FALSEALARM://TODO FIXME
			while (aInput.Next() != '*' && !aInput.EndOfStream());
			Check(!aInput.EndOfStream(),KLispErrCommentToEndOfFile);
			if (aInput.Peek() == '/')
			{
				aInput.Next();  // consume /
				goto REDO;
			}
			goto FALSEALARM;
		}
		else if (c == ';')
		{
			while (aInput.Next() != '\n' && !aInput.EndOfStream());
			goto REDO;
		}
		// parse literal strings
		else if (c == '\"')
		{
			LispString aResult;
			aResult.SetNrItems(0);
			aResult.Append(c);
			while (aInput.Peek() != '\"')
			{
				if (aInput.Peek() == '\\')
				{
					aInput.Next();
					Check(!aInput.EndOfStream(),KLispErrParsingInput);
				}
				aResult.Append(aInput.Next());
				Check(!aInput.EndOfStream(),KLispErrParsingInput);
			}
			aResult.Append(aInput.Next()); // consume the close quote
			aResult.Append('\0');
			return aHashTable.LookUp(aResult.String());
		}
		//parse atoms
		else if (IsAlpha(c) || IsSymbolic(c))
		{
			while (IsAlNum( aInput.Peek()) || IsSymbolic( aInput.Peek()))
			{
				aInput.Next();
			}
		}
		else if (c == '_')
		{
			while (aInput.Peek() == '_')
			{
				aInput.Next();
			}
		}
		else if (IsDigit(c) || c == '.')
		{
			while (IsDigit( aInput.Peek())) aInput.Next();
			if (aInput.Peek() == '.')
			{
				aInput.Next();
				while (IsDigit( aInput.Peek())) aInput.Next();
			}
			if (NumericSupportForMantissa())
			{
				if (aInput.Peek() == 'e' || aInput.Peek() == 'E')
				{
					aInput.Next();
					if (aInput.Peek() == '-' || aInput.Peek() == '+')
						aInput.Next();
					while (IsDigit( aInput.Peek())) aInput.Next();
				}
			}
		}
		// Treat the char as a space.
		else
		{
			goto REDO;
		}

FINISH://TODO FIXME
		return aHashTable.LookUpCounted(&aInput.StartPtr()[firstpos],aInput.Position()-firstpos);
	}
};