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我想应用 BNF 语法的规则来产生推导:a_Num
你的问题有点含糊。但下面是整数的 BNF (ish) 语法。
nz_digit = '1' | ... | '9'; digit = '0' | nz_digit; digitseq = digit | digitseq, digit; num = '0' | nz_digit, digitseq;