1
$\begingroup$

In relation to set theory and given a set U, what does U* mean? I'm working on homework for a programming language theory class (section on types) and one of the questions asks for the size of U*. I don't need the answer, just some help on what U* means :)

  • 3
    I believe that is the Kleene star: http://en.wikipedia.org/wiki/Kleene_star.2012-09-18

1 Answers 1

0

It means a set including every countable $U$

as a example define:

$U=\{a,b\}$

so we have:

$U^0 = \{\} = \lambda $

$U^1 = \{a,b\} = \lambda $

$U^2 = \{aa,ab,ba,bb\} = \lambda $

. . .

$U^* = \{U^0,U^1,U^2,U^3,... \}$

$U^+ = \{U^1,U^2,U^3,U^4,... \}$

  • 0
    @Henning Makholm: I meant empty a set without element do not care with notation this was why I put a equal $\lambda$ at the end of that anyway thank for notification2012-09-18