Discussion: lookups in maps

Keith keith.wygant at gmail.com
Tue Jun 9 12:02:01 UTC 2020

I usually end up writing your 'lurkup' when I use maps, so I'd like see it included.

 I don't have a better name than 'lookupWith'.

And, yeah, lookupDefault has not been useful in practice.
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On June 8, 2020 7:07:13 PM UTC, David Feuer <david.feuer at gmail.com> wrote:
>Discussion has gotten going again about harmonizing between the names
>findWithDefault and lookupDefault in containers and unordered-containers:
>    findWithDefault :: Ord k
>      => a -> k -> Map k a -> a
>    lookupDefault :: (Eq k, Hashable k)
>      => a -> k -> HashMap k a -> a
>I've been fairly unenthusiastic about adding extra names for this function
>in one package or the other, in large part because I don't like the
>function. I'd much rather have something in the spirit of `either`,
>`maybe`, `bool`, etc.:
>    lurkup :: Ord k
>       => r -> (a -> r) -> k -> Map k a -> r
>    lurkup r f k = maybe r f . lookup k
>    lookup k = lurkup Nothing Just k
>Unfortunately, I haven't been able to come up with a decent name for this
>function. Can anyone help?
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