bfs
BUTFIRSTS list
BFS list
outputs a list containing the BUTFIRST of each member of the input
list. It is an error if any member of the input list is empty or an
array. (The input itself may be empty, in which case the output is
also empty.) This could be written as
to butfirsts :list
output map "butfirst :list
end
but is provided as a primitive in order to speed up the iteration
tools MAP, MAP.SE, and FOREACH.