输入一个文法，可得到文法的FIRST集、FOLLOW集、SELECT集，可以判断文法是否为LL（1）文法，并可求出文法的预测分析表，以及串的自顶向下的分析过程。输出很清晰。-Enter a grammar, the grammar of the FIRST sets available, FOLLOW sets, SELECT set, you can determine whether the grammar LL (1) grammar, and can find the grammar of the prediction of the table, and the string of top-down analysis. Output is very clear.