Hello,
Relating to my previous message, I am wondering whether Stata's
implementation of NFA regular expressions has been documented
publicly. It is said that they are "based on Henry Spenser's NFA
algorithm, and hence are almost identical to POSIX.2 regular
expressions".
This obviously isn't a statement of equivalence, and has some
implications for writing programs that are supposed to work in the
general case.
The best thing would be a publicly available formal syntax definition
of Stata's implementation, or a statement of equivalence with a
current implementation that does have a publicly available formal
syntax definition. At minimum, a comparison of the difference between
Stata RE's and POSIX.2 or Henry Spenser's algorithm could do.
Cheers
James
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