Proposal: Add a splitBy / splitOn in Data.List

Vanessa McHale vanessa.mchale at
Fri Nov 2 12:01:35 UTC 2018

cabal now has the ability to be used for
which I think addresses your use case (at least, it's easier than
forking base...).

On 11/2/18 6:38 AM, Elliot Cameron wrote:
> Despite these subtleties, I must confess I've often wanted to whip up
> a quick script and been frustrated that these functions are missing
> from base. For example using Haskell as a sed/awk alternative can be
> pleasant *if* the functions you need are in base. What's more, in many
> years I've only really wanted one or two versions of this.
> What if we added the most flexible of versions and included only that?
> This version would accept multicharacter delimiters, always throw them
> away, and always produce a new entry in the result for every
> occurrence of the delimiter. If you don't want the empty entries, you
> can filter. If you don't want leading, you can dropWhile. If you want
> the delimiters back, you can map. This seems like a nice trade-off for
> just being available in base.
> On Fri, Nov 2, 2018, 1:51 AM Edward Kmett <ekmett at
> <mailto:ekmett at> wrote:
>     The main thing that prevented it from going into base is the
>     number of subtleties about what precisely it means to properly
>     "split" something.
>     Most languages make fairly arbitrary calls on topics such as:
>     * Do you split on list elements (e.g. ',') or list of elements, so
>     you can multi-character delimiters ", "? What about multiple types
>     of thing that are all delimiters, e.g. any whitespace character?
>     * What do you do with the delimiters?
>     * What happens with runs of delimiters? 
>     * What about initial or final runs of delimiters (e.g. leading
>     spaces)?
>     The end result was that a split package was written by Brent
>     Yorgey back in 2008 or so that rather comprehensively covers the
>     design space, and it was incorporated into the Haskell Platform.
>     -Edward
>     On Thu, Nov 1, 2018 at 1:34 PM Saurabh Nanda
>     <saurabhnanda at <mailto:saurabhnanda at>> wrote:
>         This has certainly been discussed before. A quick Google
>         search turned up the following past discussions:
>           *
>           *
>         Is there anything blocking this discussion & implementation?
>         Anything that can be done to unblock it?
>         -- Saurabh.
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*Vanessa McHale*
Functional Compiler Engineer | Chicago, IL

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