regular expression syntax

i'm wondering why * means 0 or more matches and + means 1 or more matches

i know this notation comes from formal language work and math (kleene star) but is there any reason * and + were chosen? or are they just random symbols?

j

3

w

5

Sounds like you need etymology-man to the rescue, or in this case Wikipedia.

The origins of regular expressions lie in automata theory and formal language theory, both of which are part of theoretical computer science. These fields study models of computation (automata) and ways to describe and classify formal languages. In the 1950s, mathematician Stephen Cole Kleene described these models using his mathematical notation called regular sets.[1] The SNOBOL language was an early implementation of pattern matching, but not identical to regular expressions. Ken Thompson built Kleene's notation into the editor QED as a means to match patterns in text files. He later added this capability to the Unix editor ed, which eventually led to the popular search tool grep's use of regular expressions ("grep" is a word derived from the command for regular expression searching in the ed editor: g/re/p where re stands for regular expression[2]). Since that time, many variations of Thompson's original adaptation of regular expressions have been widely used in Unix and Unix-like utilities including expr, AWK, Emacs, vi, and lex.

Also look here http://www.rand.org/pubs/research_memoranda/2008/RM704.pdf

on page 50(54 in pdf) it first defines the asterisk as a unary operator instead of a binary in 'Regular Events' in (neural) nerve nets

j3w5

Why is * for complex conjugates? Why is a bar over x indicate that x is a mean of other x's?

Why is the kanji for house a roof over a pig?

>>9
That makes me wonder, would we have a different symbol for addition if Christianity never happened?

We do have the middle dot for multiplication. For addition it seems initially people just used spaces or placing numbers side by side: http://en.wikipedia.org/wiki/History_of_mathematical_notation

Euler was the first to use the notation f(x) to represent a function of x.

I don't know about other routes, but Michiru route explains why Michiru route acts like a cliched comic relief character. I'm assuming the other characters also are who they are because of what happened in their pasts.

 That slut will take it.

 i will give you that shes in top 10

The usual, as usual. Sixth installment, for the posting of giant and tiny Touhou characters or anything similarly fitting the theme/interests here.