-- srt fn xs: sort a list by a key function.
-- Same name as srt xs (1-arg), selected by arity.
-- Sort numbers by distance from zero
dist x:n>n;abs x
by-dist xs:L n>L n;srt dist xs
-- Sort words by length
wlen s:t>n;len s
by-len ws:L t>L t;srt wlen ws
-- Sort words alphabetically (descending) using a negating trick:
-- there's no built-in reverse-sort, but srt + rev does it
by-len-desc ws:L t>L t;rev (srt wlen ws)
-- engine-skip: vm
-- run: by-dist [-3,1,-5,2]
-- out: [1, 2, -3, -5]
-- run: by-len ["banana","fig","apple","kiwi"]
-- out: [fig, kiwi, apple, banana]
-- run: by-len-desc ["banana","fig","apple","kiwi"]
-- out: [banana, apple, kiwi, fig]