Added note on PCRE backreferences

noteOnPCREBackreferences.txt

@@ -0,0 +1,7 @@
+In PCRE, following a backreference by _any_ number seems to turn it into an octal value. Why is this?
+
+Eg.
+`(a)\1` <-- Backreference
+`(a)\17` <-- Octal '17'
+`(a)\19` <-- Octal 1, then literal 9
+`(a)\1a` <-- Backreference, then 'a'

re_test.go

@@ -280,6 +280,18 @@ var reTests = []struct {
 	{`ab*`, nil, `xabyabbbz`, []Group{{1, 3}, {4, 8}}},
 	{`ab*`, nil, `xayabbbz`, []Group{{1, 2}, {3, 7}}},
 	{`[abhgefdc]ij`, nil, `hij`, []Group{{0, 3}}},
+	{`a[bcd]*dcdcde`, nil, `adcdcde`, []Group{{0, 7}}},
+	{`a[bcd]+dcdcde`, nil, `adcdcde`, []Group{}},
+	{`[a-zA-Z_][a-zA-Z0-9_]*`, nil, `alpha`, []Group{{0, 5}}},
+	{`multiple words of text`, nil, `uh-uh`, []Group{}},
+	{`multiple words`, nil, `multiple words, yeah`, []Group{{0, 14}}},
+	{`[k]`, nil, `ab`, []Group{}},
+	{`a[-]?c`, nil, `ac`, []Group{{0, 2}}},
+	{`^(.+)?B`, nil, `AB`, []Group{{0, 2}}},
+
+	// At this point, the python test suite has a bunch
+	// of backreference tests. Since my engine doesn't
+	// implement backreferences, I've skipped those tests.
 
 	// Todo - add numeric range tests
 }
@@ -326,6 +338,37 @@ var groupTests = []struct {
 	{`(abc|)ef`, nil, `abcdef`, []Match{[]Group{{4, 6}, {4, 4}}}},
 	{`(a|b)c*d`, nil, `abcd`, []Match{[]Group{{1, 4}, {1, 2}}}},
 	{`(ab|ab*)bc`, nil, `abc`, []Match{[]Group{{0, 3}, {0, 1}}}},
+	{`a([bc]*)c*`, nil, `abc`, []Match{[]Group{{0, 3}, {1, 3}}}},
+	{`a([bc]*)(c*d)`, nil, `abcd`, []Match{[]Group{{0, 4}, {1, 3}, {3, 4}}}},
+	{`a([bc]+)(c*d)`, nil, `abcd`, []Match{[]Group{{0, 4}, {1, 3}, {3, 4}}}},
+	{`a([bc]*)(c+d)`, nil, `abcd`, []Match{[]Group{{0, 4}, {1, 2}, {2, 4}}}},
+	{`(ab|a)b*c`, nil, `abc`, []Match{[]Group{{0, 3}, {0, 2}}}},
+	{`((a)(b)c)(d)`, nil, `abcd`, []Match{[]Group{{0, 4}, {0, 3}, {0, 1}, {1, 2}, {3, 4}}}},
+	{`^a(bc+|b[eh])g|.h$`, nil, `abh`, []Match{[]Group{{1, 3}}}},
+	{`(bc+d$|ef*g.|h?i(j|k))`, nil, `effgz`, []Match{[]Group{{0, 5}, {0, 5}}}},
+	{`(bc+d$|ef*g.|h?i(j|k))`, nil, `ij`, []Match{[]Group{{0, 2}, {0, 2}, {1, 2}}}},
+	{`(bc+d$|ef*g.|h?i(j|k))`, nil, `effg`, []Match{}},
+	{`(bc+d$|ef*g.|h?i(j|k))`, nil, `bcdd`, []Match{}},
+	{`(bc+d$|ef*g.|h?i(j|k))`, nil, `reffgz`, []Match{[]Group{{1, 6}, {1, 6}}}},
+	{`(((((((((a)))))))))`, nil, `a`, []Match{[]Group{{0, 1}, {0, 1}, {0, 1}, {0, 1}, {0, 1}, {0, 1}, {0, 1}, {0, 1}, {0, 1}, {0, 1}}}},
+	{`(.*)c(.*)`, nil, `abcde`, []Match{[]Group{{0, 5}, {0, 2}, {3, 5}}}},
+	{`\((.*), (.*)\)`, nil, `(a, b)`, []Match{[]Group{{0, 6}, {1, 2}, {4, 5}}}},
+
+	// At this point, the python test suite has a bunch
+	// of backreference tests. Since my engine doesn't
+	// implement backreferences, I've skipped those tests.
+
+	{`(a)(b)c|ab`, nil, `ab`, []Match{[]Group{{0, 2}}}},
+	{`(a)+x`, nil, `aaax`, []Match{[]Group{{0, 4}, {2, 3}}}},
+	{`([ac])+x`, nil, `aacx`, []Match{[]Group{{0, 4}, {2, 3}}}},
+	{`([^/]*/)*sub1/`, nil, `d:msgs/tdir/sub1/trial/away.cpp`, []Match{[]Group{{0, 17}, {7, 12}}}},
+	{`([^.]*)\.([^:]*):[T ]+(.*)`, nil, `track1.title:TBlah blah blah`, []Match{[]Group{{0, 28}, {0, 6}, {7, 12}, {14, 28}}}},
+	{`([^N]*N)+`, nil, `abNNxyzN`, []Match{[]Group{{0, 8}, {4, 8}}}},
+	{`([^N]*N)+`, nil, `abNNxyz`, []Match{[]Group{{0, 4}, {3, 4}}}},
+	{`([abc]*)x`, nil, `abcx`, []Match{[]Group{{0, 4}, {0, 3}}}},
+	{`([abc]*)x`, nil, `abc`, []Match{}},
+	{`([xyz]*)x`, nil, `abcx`, []Match{[]Group{{3, 4}, {3, 3}}}},
+	{`(a)+b|aac`, nil, `aac`, []Match{[]Group{{0, 3}}}},
 }
 
 func TestFindAllMatches(t *testing.T) {