nAry, take, unary

README.md

@@ -9,7 +9,7 @@
 <p align="center">
   <a href="https://www.npmjs.com/package/tinyfunk"><img src="https://img.shields.io/npm/v/tinyfunk.svg" alt="npm version" style="max-width:100%;"></a>
   <a href="https://www.npmjs.com/package/tinyfunk"><img src="https://img.shields.io/npm/dm/tinyfunk.svg" alt="npm downloads" style="max-width:100%;"></a>
-  <a href="#"><img src="https://img.shields.io/badge/gzip--size-1.36%20kB-blue.svg" alt="gzip-size" style="max-width:100%;"></a>
+  <a href="#"><img src="https://img.shields.io/badge/gzip--size-1.4%20kB-blue.svg" alt="gzip-size" style="max-width:100%;"></a>
   <br />
   <a href="https://travis-ci.org/flintinatux/tinyfunk"><img src="https://travis-ci.org/flintinatux/tinyfunk.svg?branch=master" alt="Build Status" style="max-width:100%;"></a>
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@@ -105,6 +105,7 @@ If you've lived with FP long enough, you are likely familiar with most of the fu
 | `match` | `RegExp -> String -> [String]` |
 | `merge` | `{ k: v } -> { k: v } -> { k: v }` |
 | `multiply` | `Number -> Number -> Number` |
+| `nAry` | `Number -> (a... -> b) -> (a... -> b)` |
 | `not` | `a -> a` |
 | `objOf` | `k -> v -> { k: v }` |
 | `omit` | `[k] -> { k: v } -> { k: v }` |
@@ -128,10 +129,12 @@ If you've lived with FP long enough, you are likely familiar with most of the fu
 | `sortBy` | `Ord b => (a -> b) -> [a] -> [a]` |
 | `split` | `RegExp -> String -> [String]` |
 | `tail` | `[a] -> [a]` |
+| `take` | `Number -> [a] -> [a]` |
 | `tap` | `(a -> b) -> a -> a` |
 | `then` | `(a -> Promise b) -> a -> Promise b` |
 | `thrush` | `a -> (a -> b) -> b` |
 | `unapply` | `([a] -> b) -> a... -> b` |
+| `unary` | `(a... -> b) -> (a -> b)` |
 | `unit` | `a -> ()` |
 | `unless` | `(a -> Boolean) -> (a -> a) -> a -> a` |
 | `useWith` | `(b... -> c) -> [(a -> b)] -> a... -> c` |

src.js

@@ -180,6 +180,11 @@ const multiply = curry((a, b) =>
   a * b
 )
 
+// nAry :: Number -> (a... -> b) -> (a... -> b)
+const nAry = curry((n, f) =>
+  unapply(compose(apply(f), take(n)))
+)
+
 // not :: a -> a
 const not = a => !a
 
@@ -290,6 +295,9 @@ const thrush = curry((x, f) =>
   f(x)
 )
 
+// unary :: (a... -> b) -> (a -> b)
+const unary = nAry(1)
+
 // unit :: a -> ()
 const unit = () => {}
 
@@ -347,6 +355,9 @@ const last = compose(head, slice(-1, void 0))
 // tail :: [a] -> [a]
 const tail = slice(1, Infinity)
 
+// take :: Number -> [a] -> [a]
+const take = slice(0)
+
 // keys :: { k: v } -> [k]
 const keys = reduceObj(_appendKey, [])
 
@@ -389,6 +400,7 @@ _assign(exports, {
   match,
   merge,
   multiply,
+  nAry,
   not,
   objOf,
   omit,
@@ -412,10 +424,12 @@ _assign(exports, {
   sortBy,
   split,
   tail,
+  take,
   tap,
   then,
   thrush,
   unapply,
+  unary,
   unit,
   unless,
   useWith,

test/nAry.js

@@ -0,0 +1,19 @@
+const { expect } = require('chai')
+
+const { nAry } = require('..')
+
+describe('nAry', () => {
+  const f = (a=0, b=0, c=0, d=0) =>
+    a + b + c + d
+
+  it('limits the args passed to the wrapped function', () => {
+    expect(nAry(0, f)(1, 1, 1, 1)).to.equal(0)
+    expect(nAry(1, f)(1, 1, 1, 1)).to.equal(1)
+    expect(nAry(2, f)(1, 1, 1, 1)).to.equal(2)
+    expect(nAry(3, f)(1, 1, 1, 1)).to.equal(3)
+  })
+
+  it('is curried', () =>
+    expect(nAry(1)(f)(1, 1, 1, 1)).to.equal(1)
+  )
+})

test/take.js

@@ -0,0 +1,20 @@
+const { expect } = require('chai')
+
+const { take } = require('..')
+
+describe('take', () => {
+  const arr = [1, 2, 3, 4]
+
+  it('takes the first n items in a list', () => {
+    expect(take(0, arr)).to.eql([])
+    expect(take(1, arr)).to.eql([1])
+    expect(take(2, arr)).to.eql([1, 2])
+    expect(take(3, arr)).to.eql([1, 2, 3])
+    expect(take(4, arr)).to.eql([1, 2, 3, 4])
+    expect(take(5, arr)).to.eql([1, 2, 3, 4])
+  })
+
+  it('is curried', () =>
+    expect(take(1)(arr)).to.eql([1])
+  )
+})

test/unary.js

@@ -0,0 +1,15 @@
+const { expect } = require('chai')
+
+const { unary } = require('..')
+
+describe('unary', () => {
+  const f = unary((a=0, b=0) =>
+    a + b
+  )
+
+  it('only passes one arg to wrapped function', () => {
+    expect(f()).to.equal(0)
+    expect(f(1)).to.equal(1)
+    expect(f(1, 2)).to.equal(1)
+  })
+})