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Asked: 2026-06-11T11:21:21+00:00

I’m trying to split the following (Delphi RTTI output) by the namespace delimiter .

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I’m trying to split the following (Delphi RTTI output) by the namespace delimiter .:

System.Generics.Collections.TEnumerator<Utils.TPair<System.string,System.string>>

The correct split should be [System, Generics, Collections, TEnumerator<Utils.TPair<System.string,System.string>>].

First I tried a negative lookahead \.(?!\<*[a-zA-Z0-9_.,]*\>), but that matched both the period in Utils.TPair and the leftmost System.string. I am a little surprised, I might add, that it (correctly) matched the period in Collections.TEnumerator. I guess this is a testament to my command of the regex language.

So I tried making it “greedier” by saying this: \.(?!\<*[a-zA-Z0-9_.,<>]*\>), but then no match was found. (I know this isn’t what regexers usually mean when they say “greedy”, but I couldn’t come up with a more suitable description.)

So I decided to go back to scratch. As far as I understand, I should be able to use negative lookarounds to solve my case. In particular: any match following < can effectively be ignored. So I decided (?<!\<[a-zA-Z0-9_]*)\. should solve my problem. It doesn’t. Which probably is due to the fact that (many) negative lookbehind implementations don’t support variable length strings. (To be specific, PCRE – which is basically what Delphi uses, apparently support variable length alternates. Every alternate has to be fixed at execution, though.)

And thus I turn to you, the Community.

Can anyone please shed some light on this problem, which actually should be quite simple? Would be great!

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1 Answer

  1. Editorial Team

    Try this regex:

    \.(?![^.]*[\w_.,]*>)

    It basically means: Match all . that are not followed by a . that is before a > und thus inside a <>.
    It is actually very limited to your example.

    See on rubular

    A negativ lookbehind can solve this task better:

    (?<!<.{0,1000})\.

    It means match any . that does not have a < before it.

    I tried this in java and it works. Java does not allow to have unlimited lookbehinds, thats why I used a limit of 1000 {0,1000} instead of *. I don’t know if PCRE supports it.

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