# Function using lambda argument. map from standard library:
def map(f): [.[] | f];
> [1,2,3] | map(. * 2)
[
  2,
  4,
  6
]
# select from standard library:
def select(f): if f then . else empty end;
> [1,2,3] | map(select(. % 2 == 0))
[
  2
]

# Function using argument binding and recursion to output multiple values
def down($n):
  if $n >= 0 then $n, down($n-1)
  else empty
  end;