private static Vector<Token> prewortDetermineUnaryOperators(Vector<Token> postfixTokens) {
		Vector<Token> outVector = postfixTokens;
		Expressions expr = Calculator.expressions;

		int tokenCount = outVector.size();
		for(int i=0;i<tokenCount;i++) {
			Token currentToken = outVector.get(i);
			String currentText = currentToken.getTokenText();
			int tokenType = currentToken.getTokenType();

			boolean isFirstToken 		 	= i==0;
			boolean canBeValidUnaryOperator = expr.matchesUnaryOperator(currentText);

			if(canBeValidUnaryOperator) {
				if(isFirstToken) {
					currentToken.setTokenType(Token.TOKEN_UNARY_OPERATOR);
				} else {
					Token prevToken = outVector.get(i-1);
					int prevType = prevToken.getTokenType();

					boolean isValidUnaryOperator = prevType==Token.TOKEN_ARGUMENT_SEPERATOR || prevType==Token.TOKEN_OPEN_BRACKET || prevType==Token.TOKEN_OPERATOR ||prevType==Token.TOKEN_UNARY_OPERATOR;
					if(isValidUnaryOperator) {
						currentToken.setTokenType(Token.TOKEN_UNARY_OPERATOR);
					}

				}
			}
		}

		return outVector;
	}