Functional way to compare things inside a list

[Chris Rebert]

On Thu, Sep 20, 2012 at 3:58 PM,  <thorsopia at lavabit.com> wrote:
> Hi,
>
> list = [{'1': []}, {'2': []}, {'3': ['4', '5']}]

Are the dictionaries each guaranteed to only contain a single
key-value pair? (Or is your example just simplistic?)

> I want to check for a value (e.g. '4'), and get the key of the dictionary
> that contains that value.

And what if there is no such dictionary? Or what if there are multiple
such dictionaries?

> (Yep, this is bizarre.)
>
> some_magic(list, '4')
> => '3'
>
> What's the functional way to do it?

Why do you care about the paradigm used?

> Is it possible to do it with a one-liner?

Who cares? It's possible to implement more complicated things in one
line of APL, but most people probably wouldn't recommend it.

Regards,
Chris R.