parseIf = do reserved "if"
             t1 <- parseTerm
             reserved "then"
             t2 <- parseTerm
             reserved "else"
             liftM (TmIf t1 t2) parseTerm
parseIf = do reserved "if"
             t1 <- parseTerm
             reserved "then"
             t2 <- parseTerm
             reserved "else"
             liftM (TmIf t1 t2) parseTerm
parseIf = do reserved "if"
             t1 <- parseTerm
             reserved "then"
             t2 <- parseTerm
             reserved "else"
             liftM (TmIf t1 t2) parseTerm