Step by Step solution about How to resolve the algorithm Associative array/Merging step by step in the Haskell programming language

The provided Haskell code defines a data type called Item which has the following fields:

• name: An optional string representing the name of the item.
• price: An optional float representing the price of the item.
• color: An optional string representing the color of the item.
• year: An optional integer representing the year the item was manufactured.

The itemFromMerge function takes two Item values as input and returns a new Item value that combines the data from both input items. For each field, if one of the input items has a value for that field, that value is used in the output item. If both input items have values for a field, the value from the first input item is used. If neither input item has a value for a field, the output item has the value Nothing.

The main function demonstrates the use of the itemFromMerge function by merging two Item values and printing the resulting value. In the example provided in the main function, the first Item value has a name, price, and color, but no year. The second Item value has no name, a different price, a different color, and a year. The itemFromMerge function combines these values to create a new Item value with a name of "Rocket Skates", a price of 12.75, a color of "yellow", and a year of 1974.

data Item = Item
  { name :: Maybe String
  , price :: Maybe Float
  , color :: Maybe String
  , year :: Maybe Int
  } deriving (Show)

itemFromMerge :: Item -> Item -> Item
itemFromMerge (Item n p c y) (Item n1 p1 c1 y1) =
  Item (maybe n pure n1) (maybe p pure p1) (maybe c pure c1) (maybe y pure y1)

main :: IO ()
main =
  print $
  itemFromMerge
    (Item (Just "Rocket Skates") (Just 12.75) (Just "yellow") Nothing)
    (Item Nothing (Just 15.25) (Just "red") (Just 1974))