substring search api

[Malcolm Wallace]

haskell at list.mightyreason.com wrote:

> Users may very well need the offsets, though.
> That means one needs to call some "length" function to get the
> offsets.

'length' of a ByteString is extremely cheap.

>  This requires forcing the whole input string to get the
> length of the second found location.

I don't see why it should force the whole input: only as much as is
needed to find the desired substring.  There is no need to call 'length'
on the tail, since it doesn't yield any interesting information.

Regards,
    Malcolm