Entry.purs

module App.Diff.Entry where

import Prelude

import Data.Either (either)
import Data.Function.Uncurried (Fn2, mkFn2)
import Data.Maybe (Maybe(..))
import Data.Pair (fst, (~))
import Foreign (Foreign)
import App.Diff.Class (Diff, recordDiff)
import Simple.JSON (E, read, write)

type Entry = { id ∷ Int, val ∷ String }

type DiffEntry = { id ∷ Diff Int, val ∷ Diff String }

diff ∷ Entry → Entry → DiffEntry
diff = recordDiff

diffEntry ∷ Fn2 Foreign Foreign (Maybe DiffEntry)
diffEntry = mkFn2 $ \left right → do
  let result = do
        left' ← read left ∷ E Entry
        right' ← read right ∷ E Entry
        diff <$> left' <*> right'
  either (const Nothing) (Just <<< fst) result

purs.txt

[1/1 TypesDoNotUnify] src/components/Diff/DiffEntry.purs:26:18

  26          diff <$> left' <*> right'
                       ^^^^^
  
  Could not match type
  
    ( id :: Int
    , val :: String
    )
  
  with type
  
    { id :: Int
    , val :: String
    }
  
  while trying to match type { id :: Int
                             , val :: String
                             }
    with type t0
                { id :: Int
                , val :: String
                }
  while checking that expression left'
    has type t0
               { id :: Int
               , val :: String
               }
  in value declaration diffEntry
  
  where t0 is an unknown type