-- Maps: M k v key-value collections.
-- Built with mmap (empty), mset, and queried with mget, mhas, mkeys, mvals.
-- Build a map and get a value
lookup>t;m=mset mmap "name" "alice";r=mget m "name";?r{t v:v;_:"missing"}
-- Check if a key exists
check>b;m=mset mmap "x" "1";mhas m "x"
-- Get all keys from a map (sorted)
keys>L t;m=mset (mset mmap "b" "2") "a" "1";mkeys m
-- Delete a key
del>b;m=mset mmap "x" "1";m=mdel m "x";mhas m "x"
-- run: lookup
-- out: alice
-- run: check
-- out: true
-- run: keys
-- out: [a, b]
-- run: del
-- out: false