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haskellbytestring

Idiomatic way to take a substring of a ByteString

I need to make extensive use of:

slice :: Int -> Int -> ByteString -> ByteString
slice start len = take len . drop start

Two part question:

  1. Does this already have a name? I can't find anything searching for that type on Hoogle, but it seems like it should be a really common need. I also tried searching for (Int, Int) -> ByteString -> ByteString and some flip'd versions of same. I also tried looking for [a] versions to see if there was a name in common use.
  2. Is there a better way to write it?

I'm suspicious that I'm doing something wrong because I strongly expected to find lots of people having gone down the same road, but my google-fu isn't finding anything.

Solution

  • The idiomatic way is via take and drop, which has O(1) complexity on strict bytestrings.

    slice is not provided, to discourage the reliance on unsafe indexing operations.