Also reuse of *Regexp nodes.
I believe this is the end of the parser.
The only non-execution code that remains is
the code to expand x{3,5} into simpler operations.
R=sam.thorogood, r
CC=golang-dev
https://golang.org/cl/4629078
Still TODO: parsing optimizations
make_perl_groups.pl is copied with minimal modifications
(just to generate Go syntax instead of C++) from RE2.
Google Inc is "The RE2 Author" of that file and is one of
the Go Authors, so copyright changed to the Go Authors instead.
R=sam.thorogood, r, fvbommel, robert.hencke
CC=golang-dev
https://golang.org/cl/4612041
Parser is a work in progress but can populate most of the
interesting parts of the data structure, so a good checkpoint.
All the complicated Perl syntax is missing, as are various
important optimizations made during parsing to the
syntax tree.
The plan is that exp/regexp's API will mimic regexp,
and exp/regexp/syntax provides the parser directly
for programs that need it (and for implementing exp/regexp).
Once finished, exp/regexp will replace regexp.
R=r, sam.thorogood, kevlar, edsrzf
CC=golang-dev
https://golang.org/cl/4538123
