public FunctionHighlighter(StyledDocument document) {
			
			document.addDocumentListener(this);
			// ׼ɫʹõʽ
			keywordStyle =document.addStyle("Keyword_Style", null);
			normalStyle = document.addStyle("Keyword_Style", null);
			//ɫ
			StyleConstants.setForeground(keywordStyle, new Color(148,0,85));
			StyleConstants.setForeground(normalStyle, Color.BLACK);

			// ׼ؼ
			keywords = new HashSet<String>();
			String[] key={
					"sin","cos","tan","arcsin","arccos","arctan",
					"sinh","cosh","tanh","log","log10","ln",
					"pow","exp","fact","mod","sqrt","cuberoot","yroot",
					"avg","sum","var","varp","stdev","stdevp",
					"clear","exit"
					};
			for(int i=0;i<key.length;++i){
				keywords.add(key[i]);
			}
		}