sunday_bed.elm

import Either
 
--main = asText (filterrr (\x -> x > 2) [1, 2, 3, 4])
main = asText (map squirtWithError [-2, -1, 0, 16, 36])
 
 
-- types
 
data Option a = None | Some a
-- Option String = None | Some String
-- Option Int = None | Some Int
-- Option [Int] = None | Some [Int]
 
-- Some 3      => [3] : has type Option Int
-- None        => [] : Option a (a is a wildcard)
-- Some "foo"  => ["foo"] : has type Option String
 
 
data TwoChoices a b = First a | Second b
 
type IntString = TwoChoices Int String
a = First 10
b = Second "hello"
 
mixedList = [First 10, Second "Romy", First 0, First 2]
sandwich = [Second "jelly", Second "bread", Second "peanut butter"]
 
-- use Either String Number, to store error messages
-- for failed computation
 
squirtWithError x =
  if x < 0
  then Either.Left "No negatives you doofus!"
  else Either.Right (sqrt x)
 
-- functions and recursion
 
sqqquare : Int -> Int
sqqquare x = x * x
 
lennngth xs =
  case xs of
    [] -> 0
    (x::rest) -> 1 + (lennngth rest)
    
mappp : (a -> b) -> [a] -> [b]
mappp funccc xs =
  case xs of
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