blank in regular expression in flex

Question

I have the following regular expression in a flex file. (.l file)

  doctype [[:blank:] \r\n]*<!DOCTYPE[^\[]*\[[[:blank:] \r\n]*

From a flex tutorial, in the pattern chapiter, I saw that flex defines '[:blank:]' as a blank or a tab.
But in the expression above, why do we need another blank after [:blank:] ?

Answer 1

The [:blank:] POSIX character class matches a space or a tab (even in the FLEX patterns manual ).

Thus, the [[:blank:] \\r\\n] character class equals [[:blank:]\\r\\n] .

Same as [rr] = [r] .