gabejohnson

<!-- Please do not remove or change this AfD message until the discussion has been closed. -->
{{Article for deletion/dated|page=PureScript (programming language)|timestamp=20171220235206|year=2017|month=December|day=20|substed=yes|help=off}}
<!-- Once discussion is closed, please place on talk page: {{Old AfD multi|page=PureScript (programming language)|date=20 December 2017|result='''keep'''}} -->
<!-- End of AfD message, feel free to edit beyond this point -->
{{multiple issues|
{{notability|Products|date=December 2017}}
{{refimprove|date=December 2017}}
{{third-party|date=December 2017}}

}}

gabejohnson

Types

In Fantasy Land, types are specified by an object containing a catamorphic method cata. cata has an arity matching the number of constructor functions belonging to each type. Each argument to cata is either:

1. a value
2. a function with an arity matching the number of arguments to the constructor function.
   1. Each function argument to cata must return a value of the same type as

gabejohnson

function _(x) {
  if (x instanceof _) return new _(x._);
  if (!(this instanceof _)) return new _(x);
  this._ = x;
}

_.mixfix = function mixfix(pattern, f) {
  const [name, ...names] = pattern.split('_');

  let startIndex = name === '' ? 1 : 0;

gabejohnson

// fix.js

//  _has :: String => Boolean
var _has = k => _[k] != null;

//  last :: Array a => a?
var last = xs => xs[xs.length-1];

//  copyArray :: Array a => Array a
var copyArray = xs => xs.slice(0);

gabejohnson

var isWrapper = Symbol('isWrapper');

function _(arg, args=[], ops=[]) {
  const myArgs = args.concat([arg]);
  const myOps = ops.slice(0);

  const f = ([op]) => (
    myOps.push(op),
    wrap(arg2 => _(arg2, myArgs, myOps), myArgs, myOps)
  );

gabejohnson

Ramda	Sanctuary
add(a, b)	add(a, b)
addIndex(f)	``
adjust(f, i, xs)	``
all(f, xs)	``
allPass(fs, x)	allPass(fs, x)
always(x)	K(x)
and(a, b)	and(a, b)
any(f, x)	``

gabejohnson

module Main where
import Prelude
import Record.Unsafe (unsafeDelete)
import Effect (Effect)
import TryPureScript (h1, text, render)

r :: forall t. Record (x :: Boolean, x :: Int, x :: String, x :: t)
r = { x: [3] } { x = true }

r2 :: forall t. Record (x :: Boolean, x :: Int, x :: String, x :: t)

gabejohnson

/* 
Calling _.foo.bar with a value returns the value at the end of that path (if it exists), `undefined` otherwise.

Constructing _.foo.bar with a function returns a function that immutably updates a value if the path matches, returns the original otherwise.

Usage:

> [{foo: {bar: 1}}, {foo: {bar: 2}}, {foo: {bar: 3}}, {foo: {bur: 4}}].map(_.foo.bar)

[1, 2, 3, undefined]

gabejohnson

// Adapted from https://github.com/russellmcc/fantasydo/blob/master/index.js
// The `monad` argument has been added to avoid modifying the prototype of
// the yielded value to provide `pure` and `bind`.
// Note:
//   This algorithm is not stack safe, and is inefficient due to the
//   requirement that we bring the generator up to the previous state on each
//   iteration.
//   I suspect it's particularly bad for arrays. I may come back to this at
//   some point to calculate just how bad it really is.
const Do = monad => genFn => {

gabejohnson

module Main where

import Prelude

import Effect (Effect)
import Data.Array (snoc)
import Data.Foldable (fold)
import Data.Tuple.Nested (type (/\), (/\))
import TryPureScript (h1, render, text)