loop

loop is a little language for the jvm. it takes advanced functional features and makes them easy and fun to use!

see for yourself

hello world →
pointer to call your attention to examples
click for more
 
  1. greet(name) ->
  print("hi, @{name}!")
  2. [1, 3, 3, 4]   # a list

{3, 3, 4, 4}   # a set => {3, 4}
  3. # a hashmap
{ 'name'    : 'Harry Potter',
  'nemesis' : 'Voldemort' }

# a tree => { 'l','o','o','p' }
[ 'o' : 2,
  'p' : 4 ,
  'l' : 1 ,
  'o' : 3 ].keySet()
  4. # a map, with symbols
{ @name    : 'Harry Potter',
  @nemesis : 'Voldemort' }

# a set, similarly => false
{ @sprinkles, @syrup, @cherry }.contains(@fudge)

  5. # transform list => [ 'STEVE', 'WOZ', 'RANDY' ]
i.toUpperCase() for i in ['steve', 'woz', 'randy']


# filter list => [ 'ipod', 'ipad', 'iphone' ]
('i' + p) for p in ['mac',
                    'pod',
                    'pad',
                    'phone'] if p.startsWith('p')

  6. # local variables, private to function
minutes(num) ->
  "@{num * year} minutes in @{num} years"
  where
    hour: 60
    day : 24 * hour
    week: 7 * day
    year: 52 * week

  7. # reverses a list => [3, 14, 15, 268]
reverse(ls) =>
  []      : []
  [x:xs]  : reverse(xs) + [x]

reverse([268, 15, 14, 3])

  8. # pattern matching + guards => 'qi'
show(host) =>
  ('Stephen ' : sur)  | sur == 'Fry'      : @qi
                      | sur == 'Colbert'  : @report
                      | else              : @boo


show('Stephen Fry')

  9. # exceptions handled with pattern matching
cleanup(file) except handler ->
  file.open().truncate()


handler(e) =>
  FileNotFoundException  : "no harm, no file"
  IOException            : "failed: @{e.message}"

  10. # sorts a list => [3, 14, 15, 268]
quicksort(ls) =>
  []      : []
  [x:xs]  : (quicksort(i for i in xs if i > x) + [x] +
             quicksort(i for i in xs if i < x))


quicksort([15, 268, 3, 14])

  11. # creates instance of Star with default age
class Star ->
  name
  mass
  age  : '4 billion years'

new Star(name: 'Proxima Centauri'
         mass: 0.123)

  12. # instance method => 'mostly'
'They mostly come at night, mostly'.substring(28)

# static method => 133434532556
`java.lang.System`.currentTimeMillis()

# constructor => Sun 15 Apr 2012 14:22:50 UTC
new java.util.Date()

# property => 1 (getTime)
new java.util.Date(1).time

here I am "adding" a method to a simple java string 

greet(name) ->
  "hi, @{name}!"

'Zaphod Beeblebrox'.greet()

loop produces clear, useful stack traces when things go wrong 

java.lang.RuntimeException: i'm complaining
    at prelude.raise(prelude.loop:9)
    at myapp.func3(my_app.loop:3)
    at myapp.func2(my_app.loop:6)
    at myapp.func1(my_app.loop:9)
    at myapp.main(my_app.loop:13)

other fun stuff