module: Enumerable: {
  all?: test :=
    { return |
      collect: { v | (return yield: False) when: test (call: v) not }
      True
    } call/cc

  any?: test :=
    { return |
      collect: { v | (return yield: True) when: test (call: v) not }
      False
    } call/cc

  none? := all?: @(/= True)
  none?: test := (any?: test) not

  one? := count: @(== True) == 1
  one?: test := count: test == 1

  map: action := collect: action

  count :=
    { n = 0
      collect: { super n += 1 }
      n
    } call

  count: test :=
    { n = 0
      collect: { v | (super n += 1) when: (test in-context call: v) }
      n
    } call

  cycle: action :=
    { collect: { v | action in-context call: v }
    } repeat

  cycle: action times: (n: Integer) :=
    { collect: { v | action in-context call: v }
    } repeat: n

  detect: test :=
    { return |
      collect: { v | (return yield: @(ok: v)) when: (test call: v) }
      @none
    } call/cc

  detect: test or: default :=
    { return |
      collect: { v | (return yield: v) when: (test call: v) }
      default
    } call/cc

  find: test := detect: test
  find: test or: default := detect: test or: default

  find-all: test :=
    { result = []
      collect: { v |
        (super result << v) when: (test call: v)
      }
      result
    } call

  select: test := find-all: test
  filter: test := find-all: test

  reject: test :=
    { result = []
      collect: { v |
        (super result << v) unless: (test call: v)
      }
      result
    } call

  partition: test :=
    @(yes: (select: test) no: (reject: test))

  find-index: test :=
    { return |
      n = 0
      collect: { v |
        (return yield: @(ok: n)) when: (test call: v)
        super n += 1
      }
      @none
    } call/cc

  find-indices: test :=
    { return |
      is = []
      n = 0
      collect: { v |
        (super is << n) when: (test call: v)
        super n += 1
      }
      is
    } call/cc

  drop: n := (as: List) drop: n

  drop-while: test := (as: List) drop-while: test

  grep: pattern &do: { v | v } :=
    { result = []
      collect: { v |
        (super super result << do call: v) when: (pattern === v)
      }
      result
    } call

  group-by: action :=
    { result = []
      collect: { v |
        res = action call: v
        result (lookup: res) match: {
          @none ->
            (super super result =
              result set: res to: [v])

          @(ok: vs) ->
            (super super result =
              result set: res to: (vs push: v))
        }
      }
      result
    } call

  include?: v := any?: @(== v)
  includes?: v := any?: @(== v)
  member?: v := any?: @(== v)
  contains?: v := any?: @(== v)

  take: n := (as: List) take: n

  first: n := take: n

  take-while: test :=
    { done |
      result = []

      collect: { v |
        (done yield: result) unless: (test call: v)
        super result << v
      }

      result
    } call/cc

  each: action :=
    { collect: action in-context
      me
    } call

  each-consecutive: n do: action :=
    { next = me as: List
      until: { next count < n } do: {
        cur = next take: n
        next = next tail
        action in-context call: cur
      }
      me
    } call

  each-slice: n do: action :=
    { next = me
      { cur = next take: n
        next = next drop: n
        action in-context call: cur
      } until: { next empty? }
      me
    } call

  each-with-index: action :=
    { n = 0
      collect: { v |
        action in-context call: (v, n)
        super n += 1
      }
      me
    } call

  reverse-each: action :=
    { (as: List) reverse each: action
      me
    } call

  sort &comparison: @<=> :=
    (as: List) sort &comparison: comparison
  sort-by: something &comparison: @<=> :=
    (as: List) sort-by: something &comparison: comparison

  zip: b &zipper: @id :=
    (as: List) zip: (b as: List) &zipper: zipper

  first :=
    { done |
      collect: { v | done yield: v }
      error: @empty
    } call/cc

  reduce: a &initial: @undefined :=
    { collect: { v |
        super initial =
          if: (initial == @undefined)
            then: { v }
            else: { a call: (v, initial) }
      }

      if: (initial == @undefined)
        then: { error: @empty }
        else: { initial }
    } call

  inject: a &initial: @undefined :=
    reduce: a &initial: initial

  maximum &comparison: @<=> :=
    reduce: { a b |
      if: (comparison call: (a, b) > 0)
        then: { a }
        else: { b }
    }

  maximum-by: comparing :=
    reduce: { a b |
      if: (comparing call: a <=> comparing call: b > 0)
        then: { a }
        else: { b }
    }

  minimum &comparison: @<=> :=
    reduce: { a b |
      if: (comparison call: (a, b) < 0)
        then: { a }
        else: { b }
    }

  minimum-by: comparing :=
    reduce: { a b |
      if: (comparing call: a <=> comparing call: b < 0)
        then: { a }
        else: { b }
    }

  minimum-maximum &comparison: @<=> :=
    @(minimium: (minimum &comparison: comparison)
        maximum: (maximum &comparison: comparison))

  minimum-maximum-by: comparing :=
    @(minimum: (minimum-by: comparing)
        maximum: (maximum-by: comparing))

  as: List :=
    { list = []
      collect: { v | super list << v }
      list
    } call

  entries := as: List
}