lassoc Òlooks upÓ a value in an association list.
lIf found, the entire pair is returned.
lIf not found, [ ] is returned.
lassoc(ÒcÓ, [[ÒaÓ, 3], [ÒbÓ, 5], [ÒcÓ, 7]]) ==> [ÒcÓ, 7]
lassoc(ÒdÓ, [[ÒaÓ, 3], [ÒbÓ, 5], [ÒcÓ, 7]]) ==> [ ]
lType signature of assoc?