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Mirrors > Home > MPE Home > Th. List > df-word | Structured version Visualization version Unicode version |
Description: Define the class of words over a set. A word (sometimes also called a string) is a finite sequence of symbols from a set (alphabet) . Definition in section 9.1 of [AhoHopUll] p. 318. The domain is forced to be an initial segment of so that two words with the same symbols in the same order be equal. The set Word is sometimes denoted by S*, using the Kleene star, although the Kleene star, or Kleene closure, is sometimes reserved to denote an operation on languages. The set Word is the free monoid over , where the monoid law is concatenation and the monoid unit is the empty word (see frmdval 17388). (Contributed by FL, 14-Jan-2014.) (Revised by Stefan O'Rear, 14-Aug-2015.) (Revised by Mario Carneiro, 26-Feb-2016.) |
Ref | Expression |
---|---|
df-word | Word ..^ |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | cS | . . 3 | |
2 | 1 | cword 13291 | . 2 Word |
3 | cc0 9936 | . . . . . 6 | |
4 | vl | . . . . . . 7 | |
5 | 4 | cv 1482 | . . . . . 6 |
6 | cfzo 12465 | . . . . . 6 ..^ | |
7 | 3, 5, 6 | co 6650 | . . . . 5 ..^ |
8 | vw | . . . . . 6 | |
9 | 8 | cv 1482 | . . . . 5 |
10 | 7, 1, 9 | wf 5884 | . . . 4 ..^ |
11 | cn0 11292 | . . . 4 | |
12 | 10, 4, 11 | wrex 2913 | . . 3 ..^ |
13 | 12, 8 | cab 2608 | . 2 ..^ |
14 | 2, 13 | wceq 1483 | 1 Word ..^ |
Colors of variables: wff setvar class |
This definition is referenced by: iswrd 13307 wrdval 13308 nfwrd 13333 csbwrdg 13334 |
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