filter.md

filter, filter-out

Filters a collection

Expects a function in its arguments and a collection to filter in its arguments or as the incoming "ret".

Fails if the collection or the function is missing.

filter [ 1, 2, 3, 4, 5 ]
  def x
    = (x % 2) 1

# f.ret --> [ 1, 3, 5 ]

with objects (hashes)

filter { a: 'A', b: 'B', c: 'C', d: 'D' }
  def k v i
    #or (k == 'a') (v == 'C') (i == 3)
    k == 'a' or v == 'C' or i == 3

# f.ret --> { 'a' => 'A', 'c' => 'C', 'd' => 'D' }

filter-out

Is the negative sibling of "filter".

filter-out [ 1, 2, 3, 4, 5 ]
  def x
    = (x % 2) 0

# f.ret --> [ 1, 3, 5 ]

incoming ret

When not given directly a collection, filter takes it from the incoming "ret"

{ a: 'A', b: 'B', c: 'C', d: 'D' }
filter
  def k v i l # key, value, index, length
    i = (l - 1) or i = (l - 2)
# f.ret --> { 'c' => 'C', 'd' => 'D' }

iterating and functions

Iterating functions accept 0 to 3 arguments when iterating over an array and 0 to 4 arguments when iterating over an object.

Those arguments are [ value, index, length ] for arrays. They are [ key, value, index, length ] for objects.

The corresponding key, val, idx and len variables are also set in the closure for the function call.

see also

map, select, and reject.

• source
• filter spec