aivi.core.fn

Higher-order function combinators. This module provides building blocks for working with functions as first-class values — composing, flipping, and applying them in pipelines.

use aivi.core.fn (
    identity
    const
    flip
    compose
    andThen
    always
    on
    applyTo
    applyTwice
)

At a glance

Function	Type	Use it for
identity	A -> A	Return a value unchanged
const	A -> B -> A	Ignore the second argument and keep the first
flip	(A -> B -> C) -> B -> A -> C	Reverse the first two arguments of a function
compose	(B -> C) -> (A -> B) -> A -> C	Right-to-left composition
andThen	(A -> B) -> (B -> C) -> A -> C	Left-to-right composition
always	A -> B -> A	Constant function with a more intention-revealing name
on	(B -> B -> C) -> (A -> B) -> A -> A -> C	Compare or combine after projecting both sides
applyTo	A -> (A -> B) -> B	Value-first application
applyTwice	(A -> A) -> A -> A	Apply the same transform two times

---

identity

Returns its argument unchanged. Useful as a no-op transformer in pipelines.

use aivi.core.fn (identity)

type Int -> Int
func keepAsIs = n =>
    identity n

---

const

Returns a function that always returns its first argument, ignoring the second. Useful for discarding an input in a pipeline step.

use aivi.core.fn (const)

type Text -> Int
func alwaysForty = ignored =>
    const 42 ignored

---

flip

Reverses the order of the first two arguments of a two-argument function.

use aivi.core.fn (flip)

use aivi.math (clamp)

type Int -> Int -> Int -> Int
func clampFlipped = high low n =>
    flip clamp high low n

---

compose

Composes two functions, applying g first and then f. compose f g x is equivalent to f (g x).

use aivi.core.fn (compose)

use aivi.math (
    negate
    abs
)

type Int -> Int
func negAbs = n =>
    compose negate abs n

---

andThen

Applies f first and then g. The reverse of compose. andThen f g x is equivalent to g (f x). Often called "left-to-right composition" or >>>.

use aivi.core.fn (andThen)

use aivi.math (
    abs
    negate
)

type Int -> Int
func absNeg = n =>
    andThen abs negate n

---

always

Returns a function that ignores its argument and always returns the given value. Equivalent to const with argument order swapped.

use aivi.core.fn (always)

type Text -> Int
func constantZero = ignored =>
    always 0 ignored

---

on

Applies a transformation f to both arguments before combining them with combine. Useful for comparing or combining values after mapping.

use aivi.core.fn (on)

use aivi.math (abs)

type Int -> Int -> Bool
func byInt = left right =>
    left < right

type Int -> Int -> Bool
func absCompare = x y =>
    on byInt abs x y

---

applyTo

Applies a function to a value. applyTo x f is equivalent to f x. Useful for making value-first pipelines.

use aivi.core.fn (applyTo)

use aivi.math (abs)

type Int -> Int
func applyAbs = n =>
    applyTo n abs

---

applyTwice

Applies a function to itself twice: applyTwice f x is equivalent to f (f x).

use aivi.core.fn (applyTwice)

use aivi.math (square)

type Int -> Int
func fourthPower = n =>
    applyTwice square n