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lib/kitchen-sink/function.ex
defmodule KitchenSink.Function do
@moduledoc """
this module is for higher order functions
"""
@doc """
reverses the arguments of a function.
"""
def reverse(fun) when is_function(fun, 2) do
fn(arg1, arg2) -> fun.(arg2, arg1) end
end
@doc """
returns the objects you give it. useful in Enum.flat_map, or Enum.filter
"""
def identity(x), do: x
@doc """
executes a value over a list of functions (this is functional composition without macros)
"""
def pipe(functions) when is_list(functions) do
fn(input) ->
Enum.reduce(functions, input, fn (fun, acc) ->
fun.(acc)
end)
end
end
@doc """
executes a value over a list of functions in reverse order (this is functional composition without macros)
"""
def compose(functions) when is_list(functions) do
functions
|> Enum.reverse
|> pipe
end
@doc """
from clojure. takes in a list of functions, outputs a function that takes in a list of values, then applies the
functions to each value. sorta like a super Enum.map
"""
def juxt(functions) when is_list(functions) do
#good for optimiztion
super_fun = fn x -> Enum.map(functions, fn fun -> fun.(x) end) end
fn(input_list) ->
Enum.map(input_list, super_fun)
end
end
end