List Commands Library for 50g

[pier4r]

2b.

For me I would choose actually 1 but for a practical perspective a lot of people do Stack acrobatics so the 2b would be the most reasonable:
L2: second split
L1: first split



Aside from that, I did not yet test KSORT and other overlooked commands but I am going to request commands to handle a sort of "associative" list.

Given a list of sublists that follows a certain format (when not, it is the user fault, the program has not to check the entire input), in particular:
{ {k1 v1} {k2 v2} ... {kn vn}}

Where k1 is the key and v1 is the value (the position may be also inverted, the important part is that it is well defined in the documentation).

Could be possible to have commands that sorts this list by value or by key?
A command that returns if a key exists (and how many times)?
A command that returns if a value exists (and how many times)?

Of course those are heavily nice to have commands, but since the library is already so beautiful, I ask.

edit: I am already happy if the above commands are done for keys as integers/string/reals and values only as reals.