[Issue 11765] New: std.regex: Negation of character class is not applied to base class first

[d-bugmail at puremagic.com]

https://d.puremagic.com/issues/show_bug.cgi?id=11765

           Summary: std.regex: Negation of character class is not applied
                    to base class first
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Phobos
        AssignedTo: nobody at puremagic.com
        ReportedBy: andrej.mitrovich at gmail.com


--- Comment #0 from Andrej Mitrovic <andrej.mitrovich at gmail.com> 2013-12-18 11:37:06 PST ---
-----
import std.regex;
import std.stdio;

void main()
{
    // expected: [["3"]] - but got: [["2"]]]
    writeln("123456789".match("[^1--[2]]"));

    // the above is *currently* equivalent to:
    writeln("123456789".match("[^[1--[2]]]"));

    // which means: subtract "1 - 2" (equals 1),
    // and then negate it (so "2" will match first in the string)

    // but I expect the first case to be equivalent to:
    writeln("123456789".match("[[^1]--[2]]"));

    // which means: negate 1 (for discussion assume 2-9 range),
    // subtract 2 and you get 3-9, which means "3" will match first.
}
-----

I'm not sure whether this is just how ECMAScript does it (since std.regex
references it), but e.g. .NET does negation on the base class first (The "1"
class above) and *then* it does subtraction with another class.

You can test this behavior here:

http://refiddle.com/

Using .net syntax:
[^01-[2]]
0123456789

It matches "3".

Either way if this report is invalid (e.g. expected behavior) then I think we
should update the docs so they state the precedence of the negation.

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