Let ∑~* be the free monoid generated by (finite) alphabet ∑. An dement of ∑ is called a letter, an dement of ∑~* and a subset of ∑~* are respectively called a word and a language. The identity of ∑~* is called a...Let ∑~* be the free monoid generated by (finite) alphabet ∑. An dement of ∑ is called a letter, an dement of ∑~* and a subset of ∑~* are respectively called a word and a language. The identity of ∑~* is called an empty word which is denoted by A; we use the notation ∑^+=∑~*-{A}. For any word x, we define lg(x) as the number of letters in x, which is called the length of x.展开更多
基金Proiect supported by the National Natural Science Foundation of China
文摘Let ∑~* be the free monoid generated by (finite) alphabet ∑. An dement of ∑ is called a letter, an dement of ∑~* and a subset of ∑~* are respectively called a word and a language. The identity of ∑~* is called an empty word which is denoted by A; we use the notation ∑^+=∑~*-{A}. For any word x, we define lg(x) as the number of letters in x, which is called the length of x.
