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Allow back references to refer to a capture that hasn't happened yet ("forward reference").

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Fixes https://github.com/boostorg/regex/issues/133.
This commit is contained in:
jzmaddock
2021-10-08 14:51:01 +01:00
parent 732d9755bd
commit 74347b95af
5 changed files with 29 additions and 73 deletions
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14
test/regress/test_backrefs.cpp
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@ -19,13 +19,15 @@ void test_backrefs()
{
using namespace boost::regex_constants;
TEST_INVALID_REGEX("a(b)\\2c", perl);
TEST_INVALID_REGEX("a(b\\1)c", perl);
//TEST_INVALID_REGEX("a(b\\1)c", perl);
TEST_REGEX_SEARCH("a(b*)c\\1d", perl, "abbcbbd", match_default, make_array(0, 7, 1, 3, -2, -2));
TEST_REGEX_SEARCH("a(b*)c\\1d", perl, "abbcbd", match_default, make_array(-2, -2));
TEST_REGEX_SEARCH("a(b*)c\\1d", perl, "abbcbbbd", match_default, make_array(-2, -2));
TEST_REGEX_SEARCH("^(.)\\1", perl, "abc", match_default, make_array(-2, -2));
TEST_REGEX_SEARCH("a([bc])\\1d", perl, "abcdabbd", match_default, make_array(4, 8, 5, 6, -2, -2));
TEST_REGEX_SEARCH("a\\([bc]\\)\\1d", basic, "abcdabbd", match_default, make_array(4, 8, 5, 6, -2, -2));
TEST_REGEX_SEARCH("(\\2two|(one))+", perl, "oneonetwo", match_default, make_array(0, 9, 3, 9, 0, 3, -2, -2));
TEST_INVALID_REGEX("(\\3two|(one))+", perl);
// strictly speaking this is at best ambiguous, at worst wrong, this is what most
// re implimentations will match though.
TEST_REGEX_SEARCH("a(([bc])\\2)*d", perl, "abbccd", match_default, make_array(0, 6, 3, 5, 3, 4, -2, -2));
@ -59,7 +61,7 @@ void test_backrefs()
// Now test the \g version:
//
TEST_INVALID_REGEX("a(b)\\g2c", perl);
TEST_INVALID_REGEX("a(b\\g1)c", perl);
//TEST_INVALID_REGEX("a(b\\g1)c", perl);
TEST_INVALID_REGEX("a(b\\g0)c", perl);
TEST_REGEX_SEARCH("a(b*)c\\g1d", perl, "abbcbbd", match_default, make_array(0, 7, 1, 3, -2, -2));
TEST_REGEX_SEARCH("a(b*)c\\g1d", perl, "abbcbd", match_default, make_array(-2, -2));
@ -67,8 +69,10 @@ void test_backrefs()
TEST_REGEX_SEARCH("^(.)\\g1", perl, "abc", match_default, make_array(-2, -2));
TEST_REGEX_SEARCH("a([bc])\\g1d", perl, "abcdabbd", match_default, make_array(4, 8, 5, 6, -2, -2));
TEST_INVALID_REGEX("a(b)\\g{2}c", perl);
TEST_INVALID_REGEX("a(b\\g{1})c", perl);
//TEST_INVALID_REGEX("a(b\\g{1})c", perl);
TEST_INVALID_REGEX("a(b\\g{0})c", perl);
TEST_REGEX_SEARCH("(\\g{2}two|(one))+", perl, "oneonetwo", match_default, make_array(0, 9, 3, 9, 0, 3, -2, -2));
TEST_INVALID_REGEX("(\\g{3}two|(one))+", perl);
TEST_REGEX_SEARCH("a(b*)c\\g{1}d", perl, "abbcbbd", match_default, make_array(0, 7, 1, 3, -2, -2));
TEST_REGEX_SEARCH("a(b*)c\\g{1}d", perl, "abbcbd", match_default, make_array(-2, -2));
TEST_REGEX_SEARCH("a(b*)c\\g{1}d", perl, "abbcbbbd", match_default, make_array(-2, -2));
@ -76,7 +80,7 @@ void test_backrefs()
TEST_REGEX_SEARCH("a([bc])\\g{1}d", perl, "abcdabbd", match_default, make_array(4, 8, 5, 6, -2, -2));
// And again but with negative indexes:
TEST_INVALID_REGEX("a(b)\\g-2c", perl);
TEST_INVALID_REGEX("a(b\\g-1)c", perl);
//TEST_INVALID_REGEX("a(b\\g-1)c", perl);
TEST_INVALID_REGEX("a(b\\g-0)c", perl);
TEST_REGEX_SEARCH("a(b*)c\\g-1d", perl, "abbcbbd", match_default, make_array(0, 7, 1, 3, -2, -2));
TEST_REGEX_SEARCH("a(b*)c\\g-1d", perl, "abbcbd", match_default, make_array(-2, -2));
@ -84,7 +88,7 @@ void test_backrefs()
TEST_REGEX_SEARCH("^(.)\\g1", perl, "abc", match_default, make_array(-2, -2));
TEST_REGEX_SEARCH("a([bc])\\g1d", perl, "abcdabbd", match_default, make_array(4, 8, 5, 6, -2, -2));
TEST_INVALID_REGEX("a(b)\\g{-2}c", perl);
TEST_INVALID_REGEX("a(b\\g{-1})c", perl);
//TEST_INVALID_REGEX("a(b\\g{-1})c", perl);
TEST_REGEX_SEARCH("a(b*)c\\g{-1}d", perl, "abbcbbd", match_default, make_array(0, 7, 1, 3, -2, -2));
TEST_REGEX_SEARCH("a(b*)c\\g{-1}d", perl, "abbcbd", match_default, make_array(-2, -2));
TEST_REGEX_SEARCH("a(b*)c\\g{-1}d", perl, "abbcbbbd", match_default, make_array(-2, -2));