Token lookahead = st.lookahead();
if(lookahead.getType().equals(Token.Type.SYMBOL)) {
SymbolToken sym = (SymbolToken)lookahead;
if(Character.isUpperCase(sym.getSymbol().charAt(0))) {
st.eat();
return new FaspVariable(sym.getSymbol());
} else {
throw new ParseException(st,"variable","constant");
}
} else {
throw new ParseException(st,"variable",st.lookahead().toString());