PureScript Night recap

• Tuesday night, we had our first PureScript Meetup!

Here are some of my notes!

JS issues … why PureScript

• JS had for Phil, an inability to reason about code
• scaling up/ getting up to speed with a large code-base is often difficult
• PureScript produces minimal and easily readable JS
• it doesn’t contain bloated libraries; you use more of only what you need
• Haskell beginners can contribute
• it has a fast runtime system
• strong expressive types
• there is more predictability of code from PureScript to JS

Why he wrote a language vs taking it off the shelf

• TypeScript/Flow vs PureScript
  • real row polymorphism from type checker
  • ADTs
• Haste/Fay
  • Fay didn’t include typeclasses support
  • GHCJS was not easy to read for JS team
  • didn’t have runtime
  • Roy (programming language) was the closest that satisfied what he wanted

Resources

• Pursuit - PureScript documentation (built with Yesod)
  • PureScript Contrib
  • PureScript Node
  • PureScript web
• Core libraries
  • !!YPER (server side rendered), uses type system to enforce certain things
  • Pux (for front end applications)
  • PureScript Halogen (100% PureScript)

Applications

• Slamdata has 100% PureScript on front end (developed Halogen)
• Quicktype -IDL
• Insect (a personal favourite of mine! )

Getting Started

• install pureScript contrib
• most people use pulp
• book (PureScript by example)
• Getting started with PureScript (pureScript documentation)

Future Work

• ApplicativeDo
• SAT Solvers (constraints/ solutions)
• parsing JSON
• argonaut
• simple generics

CodeGen talk

• Brady did a talk on using CodeGen in PureScript from Haskell Types

After Meetup-hangout

• We went out for drinks afterwards at the Arts District Brewery. It was really fun! Phil was also kind enough to give two of us a ride home. :) I have a lot of great expectations for this group!

This led to my writing my first PureScript programme!

• I started a repo with such projects, as I continue attending the Meetup and work on PureScript on my own.

On my own

• started going through the documentation

Easy to get set up

• It’s surprisingly easy to get up and running with PureScript. Here is checking the type of “map”.

• They have you do Euler question number 1. I’ve done it in Python before, so that was my comparison

• The prompt upon leaving

• Obligatory “Hello World” in PureScript

• installing pureScript-global and browsing the module

• solution for my exercise from my first programme

Katas

• Find number of non-even substrings in a string integer

def solve(s):
  arr = []
  import itertools
  a = (s[i:j] for i, j in itertools.combinations(xrange(len(s)+1), 2))
  for i in a:
    if int(i) % 2 != 0:
      arr.append(i)
  return len(arr)

• Find number in word and return its integer equivalent

function findNum(n){
  result = 0
  n = n.toLowerCase()
  var a = n.replace(/[^\w\s!.]/g,'');
  var b = a.replace(/ /g,'')
  for (var i = 0; i < b.length; i++){
    if (b.indexOf('one') !== -1){
      result = 1
    }
    else if (b.indexOf('two') !== -1){
      result = 2 
    }
    else if (b.indexOf('three') !== -1){
      result = 3
    }
    else if (b.indexOf('four') !== -1){
      result = 4
    }
    else if (b.indexOf('five') !== -1){
      result = 5
    }
    else if (b.indexOf('six') !== -1){
      result = 6
    }
    else if (b.indexOf('seven') !== -1){
      result = 7
    }
    else if (b.indexOf('eight') !== -1){
      result = 8
    }
    else if (b.indexOf('nine') !== -1){
      result = 9
    }
    else if (b.indexOf('ten') !== -1){
      result = 10
    }
  }
  return result
}

• take an array, sort it in desc order and add liftoff essentially

function liftoff(instructions){
    instructions = instructions.sort((a, b) => a - b);
    var a = instructions.reverse()
    var b  = a.join(' ') + ' liftoff!'
    return(b)
}

• collatz conjecture..count how long it takes number to reach it…

def get_collatz(n):
    #print n 
    count = 0 
    while (not n == 1):
      if n % 2 == 0:
        n = n / 2 
        count = count + 1 
      else:
        n = (3 * n) + 1 
        count = count + 1 
    return count

• return day given digit eg 1 == Monday, etc

function whatday(num) { 
  if ((num) == 1){
    return 'Sunday'
  }
  else if ((num == 2)){
    return 'Monday'
  }
  else if ((num == 3)){
    return 'Tuesday'
  }
    else if ((num == 4)){
    return 'Wednesday'
  }
  else if ((num == 5)){
    return 'Thursday'
  }
    else if ((num == 6)){
    return 'Friday'
  }
    else if ((num == 7)){
    return 'Saturday'
  }
  else{
    return 'Wrong, please enter a number between 1 and 7'
  }

• check if string includes ‘tree fiddy’ or ‘3.50’ or ‘three fifty’

function isLockNessMonster(s) {
    var a = 'tree fiddy'
    var b = '3.50'
    var c = 'three fifty'
    
    if (s.includes(a) || s.includes(b) || s.includes(c)){
      return true
    }
      else{
        return false
      }
    return
}

• Armstrong number. If for each digit raised to pow 3, total/sum is the number, return true

function armstrong(num){
  var a = num.toString()
  var b = a.split("")
  var total = 0
  for (var i = 0; i < b.length; i++)
  {
    var c = Math.pow(parseInt(b[i]), 3)
    total = total + c
  }
  if (total == num){
    return(true)
  }
  else{
    return(false)
  }
  return
}

• turn num to binary string

def int_to_bin(x):
	z = str(bin(x));
	return z[2:]