On Saturday, 19 December 2020 at 23:16:18 UTC, kdevel wrote:
On Saturday, 19 December 2020 at 12:52:54 UTC, Виталий Фадеев
wrote:
Goal:
size_t pos = findRegexBackward( r"abc"d );
assert( pos == 4 );
module LastOccurrence;
size_t findRegexBackward_1 (dstring s, dstring pattern)
{
import std.regex : matchAll;
auto results = matchAll (s, pattern);
if (results.empty)
throw new Exception ("could not match");
size_t siz;
foreach (rm; results)
siz = rm.pre.length;
return siz;
}
size_t findRegexBackward_2 (dstring s, dstring pattern)
// this does not work with irreversible patterns ...
{
import std.regex : matchFirst;
import std.array : array;
import std.range: retro;
auto result = matchFirst (s.retro.array,
pattern.retro.array);
if (result.empty)
throw new Exception ("could not match");
return result.post.length;
}
unittest {
import std.exception : assertThrown;
static foreach (f; [&findRegexBackward_1,
&findRegexBackward_2]) {
assert (f ("abc3abc7", r""d) == 8);
assert (f ("abc3abc7", r"abc"d) == 4);
assertThrown (f ("abc3abc7", r"abx"d));
assert (f ("abababababab", r"ab"d) == 10);
}
}
Thanks.
But, not perfect.
We can't use reverse, becausу "ab\w" will be "w\ba" ( expect
matching "abc". revesed is "cba" ).
size_t findRegexBackward_2 (dstring s, dstring pattern)
...
assert (f ("abc3abc7", r"ab\w"d) == 4);
...
Of course, I using matchAll. But it scan all text in forward
direction.
size_t findRegexBackward_1 (dstring s, dstring pattern)
/** */
size_t findRegexBackwardMatchCase( dstring s, dstring needle,
out size_t matchedLength )
{
auto matches = matchAll( s, needle );
if ( matches.empty )
{
return -1;
}
else
{
auto last = matches.front;
foreach ( m; matches )
{
last = m;
}
matchedLength = last.hit.length;
return last.pre.length;
}
}
Thank!
Fastest solution wanted!
May be... some like a "RightToLeft" in Win32 API...
https://docs.microsoft.com/en-us/dotnet/api/system.text.regularexpressions.regexoptions?view=net-5.0#System_Text_RegularExpressions_RegexOptions_RightToLeft
but how on Linux? MS-regex and Linux-regex is identical ?
