Haskell, Aeson - Is there a better way of getting the info I need from USDA database?









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I'm a Haskell beginner trying to learn JSON parsing by going through USDA database.



I want to get the value of "ndbno" key from this link
https://api.nal.usda.gov/ndb/search/?format=json&q=potato+salad&sort=n&max=25&offset=0&api_key=DEMO_KEY



The JSON file from that link looks like this:



{
"list": {
"q": "potato salad",
"sr": "1",
"ds": "any",
"start": 0,
"end": 25,
"total": 251,
"group": "",
"sort": "n",
"item": [

"offset": 0,
"group": "Branded Food Products Database",
"name": "AHOLD, DEVILED EGG POTATO SALAD, UPC: 688267141584",
"ndbno": "45044170",
"ds": "LI",
"manu": "Ahold USA, Inc."
,

"offset": 1,
"group": "Branded Food Products Database",
"name": "AHOLD, REDSKIN POTATO SALAD, UPC: 688267141591",
"ndbno": "45044169",
"ds": "LI",
"manu": "Ahold USA, Inc."
,
...


"nbdno" key is 4th in "item"



-# LANGUAGE DeriveGeneric #-

module Lib
( someFunc
) where


import Data.Aeson
import Data.HashMap.Strict as HS
import Data.List as L
import Data.Maybe
import Data.Text
import Data.Vector as V
import GHC.Generics
import Network.HTTP.Conduit
import Text.Pretty.Simple


data Food = Name (String, Text)
| Stuff (String, Int)
deriving (Eq, Read, Show, Generic)



someFunc :: IO ()
someFunc = putStrLn "Under Consruction!"


apiKey = "https://api.nal.usda.gov/ndb/search/?format=json&q=chana+dal&sort=n&max=25&offset=0&api_key=jJN9dsKFe507qjLVqbecijtrYB4AiojXVIt1EaEZ"


instance FromJSON Food


unString x = case x of
String x -> x

unObject x = case x of
Object x -> x

unArray x = case x of
Array x -> x


getParsed :: IO ()
getParsed = do
x <- simpleHttp apiKey
let y = (unObject . snd . L.head . HS.toList . fromJust) (decode x :: Maybe Object)
z = (unArray . snd . L.last . L.init) (HS.toList y)
a = V.map (unpack . unString . snd . L.head . L.drop 5 . HS.toList . unObject) z
b = V.map (x -> read x :: Int) a
pPrint b


The way I implemented it is quite messy, but it gets the job done.



It's just that the code looks really bad and almost impossible to read. So I was wondering if there's a better way of doing that.










share|improve this question



























    up vote
    2
    down vote

    favorite
    1












    I'm a Haskell beginner trying to learn JSON parsing by going through USDA database.



    I want to get the value of "ndbno" key from this link
    https://api.nal.usda.gov/ndb/search/?format=json&q=potato+salad&sort=n&max=25&offset=0&api_key=DEMO_KEY



    The JSON file from that link looks like this:



    {
    "list": {
    "q": "potato salad",
    "sr": "1",
    "ds": "any",
    "start": 0,
    "end": 25,
    "total": 251,
    "group": "",
    "sort": "n",
    "item": [

    "offset": 0,
    "group": "Branded Food Products Database",
    "name": "AHOLD, DEVILED EGG POTATO SALAD, UPC: 688267141584",
    "ndbno": "45044170",
    "ds": "LI",
    "manu": "Ahold USA, Inc."
    ,

    "offset": 1,
    "group": "Branded Food Products Database",
    "name": "AHOLD, REDSKIN POTATO SALAD, UPC: 688267141591",
    "ndbno": "45044169",
    "ds": "LI",
    "manu": "Ahold USA, Inc."
    ,
    ...


    "nbdno" key is 4th in "item"



    -# LANGUAGE DeriveGeneric #-

    module Lib
    ( someFunc
    ) where


    import Data.Aeson
    import Data.HashMap.Strict as HS
    import Data.List as L
    import Data.Maybe
    import Data.Text
    import Data.Vector as V
    import GHC.Generics
    import Network.HTTP.Conduit
    import Text.Pretty.Simple


    data Food = Name (String, Text)
    | Stuff (String, Int)
    deriving (Eq, Read, Show, Generic)



    someFunc :: IO ()
    someFunc = putStrLn "Under Consruction!"


    apiKey = "https://api.nal.usda.gov/ndb/search/?format=json&q=chana+dal&sort=n&max=25&offset=0&api_key=jJN9dsKFe507qjLVqbecijtrYB4AiojXVIt1EaEZ"


    instance FromJSON Food


    unString x = case x of
    String x -> x

    unObject x = case x of
    Object x -> x

    unArray x = case x of
    Array x -> x


    getParsed :: IO ()
    getParsed = do
    x <- simpleHttp apiKey
    let y = (unObject . snd . L.head . HS.toList . fromJust) (decode x :: Maybe Object)
    z = (unArray . snd . L.last . L.init) (HS.toList y)
    a = V.map (unpack . unString . snd . L.head . L.drop 5 . HS.toList . unObject) z
    b = V.map (x -> read x :: Int) a
    pPrint b


    The way I implemented it is quite messy, but it gets the job done.



    It's just that the code looks really bad and almost impossible to read. So I was wondering if there's a better way of doing that.










    share|improve this question

























      up vote
      2
      down vote

      favorite
      1









      up vote
      2
      down vote

      favorite
      1






      1





      I'm a Haskell beginner trying to learn JSON parsing by going through USDA database.



      I want to get the value of "ndbno" key from this link
      https://api.nal.usda.gov/ndb/search/?format=json&q=potato+salad&sort=n&max=25&offset=0&api_key=DEMO_KEY



      The JSON file from that link looks like this:



      {
      "list": {
      "q": "potato salad",
      "sr": "1",
      "ds": "any",
      "start": 0,
      "end": 25,
      "total": 251,
      "group": "",
      "sort": "n",
      "item": [

      "offset": 0,
      "group": "Branded Food Products Database",
      "name": "AHOLD, DEVILED EGG POTATO SALAD, UPC: 688267141584",
      "ndbno": "45044170",
      "ds": "LI",
      "manu": "Ahold USA, Inc."
      ,

      "offset": 1,
      "group": "Branded Food Products Database",
      "name": "AHOLD, REDSKIN POTATO SALAD, UPC: 688267141591",
      "ndbno": "45044169",
      "ds": "LI",
      "manu": "Ahold USA, Inc."
      ,
      ...


      "nbdno" key is 4th in "item"



      -# LANGUAGE DeriveGeneric #-

      module Lib
      ( someFunc
      ) where


      import Data.Aeson
      import Data.HashMap.Strict as HS
      import Data.List as L
      import Data.Maybe
      import Data.Text
      import Data.Vector as V
      import GHC.Generics
      import Network.HTTP.Conduit
      import Text.Pretty.Simple


      data Food = Name (String, Text)
      | Stuff (String, Int)
      deriving (Eq, Read, Show, Generic)



      someFunc :: IO ()
      someFunc = putStrLn "Under Consruction!"


      apiKey = "https://api.nal.usda.gov/ndb/search/?format=json&q=chana+dal&sort=n&max=25&offset=0&api_key=jJN9dsKFe507qjLVqbecijtrYB4AiojXVIt1EaEZ"


      instance FromJSON Food


      unString x = case x of
      String x -> x

      unObject x = case x of
      Object x -> x

      unArray x = case x of
      Array x -> x


      getParsed :: IO ()
      getParsed = do
      x <- simpleHttp apiKey
      let y = (unObject . snd . L.head . HS.toList . fromJust) (decode x :: Maybe Object)
      z = (unArray . snd . L.last . L.init) (HS.toList y)
      a = V.map (unpack . unString . snd . L.head . L.drop 5 . HS.toList . unObject) z
      b = V.map (x -> read x :: Int) a
      pPrint b


      The way I implemented it is quite messy, but it gets the job done.



      It's just that the code looks really bad and almost impossible to read. So I was wondering if there's a better way of doing that.










      share|improve this question















      I'm a Haskell beginner trying to learn JSON parsing by going through USDA database.



      I want to get the value of "ndbno" key from this link
      https://api.nal.usda.gov/ndb/search/?format=json&q=potato+salad&sort=n&max=25&offset=0&api_key=DEMO_KEY



      The JSON file from that link looks like this:



      {
      "list": {
      "q": "potato salad",
      "sr": "1",
      "ds": "any",
      "start": 0,
      "end": 25,
      "total": 251,
      "group": "",
      "sort": "n",
      "item": [

      "offset": 0,
      "group": "Branded Food Products Database",
      "name": "AHOLD, DEVILED EGG POTATO SALAD, UPC: 688267141584",
      "ndbno": "45044170",
      "ds": "LI",
      "manu": "Ahold USA, Inc."
      ,

      "offset": 1,
      "group": "Branded Food Products Database",
      "name": "AHOLD, REDSKIN POTATO SALAD, UPC: 688267141591",
      "ndbno": "45044169",
      "ds": "LI",
      "manu": "Ahold USA, Inc."
      ,
      ...


      "nbdno" key is 4th in "item"



      -# LANGUAGE DeriveGeneric #-

      module Lib
      ( someFunc
      ) where


      import Data.Aeson
      import Data.HashMap.Strict as HS
      import Data.List as L
      import Data.Maybe
      import Data.Text
      import Data.Vector as V
      import GHC.Generics
      import Network.HTTP.Conduit
      import Text.Pretty.Simple


      data Food = Name (String, Text)
      | Stuff (String, Int)
      deriving (Eq, Read, Show, Generic)



      someFunc :: IO ()
      someFunc = putStrLn "Under Consruction!"


      apiKey = "https://api.nal.usda.gov/ndb/search/?format=json&q=chana+dal&sort=n&max=25&offset=0&api_key=jJN9dsKFe507qjLVqbecijtrYB4AiojXVIt1EaEZ"


      instance FromJSON Food


      unString x = case x of
      String x -> x

      unObject x = case x of
      Object x -> x

      unArray x = case x of
      Array x -> x


      getParsed :: IO ()
      getParsed = do
      x <- simpleHttp apiKey
      let y = (unObject . snd . L.head . HS.toList . fromJust) (decode x :: Maybe Object)
      z = (unArray . snd . L.last . L.init) (HS.toList y)
      a = V.map (unpack . unString . snd . L.head . L.drop 5 . HS.toList . unObject) z
      b = V.map (x -> read x :: Int) a
      pPrint b


      The way I implemented it is quite messy, but it gets the job done.



      It's just that the code looks really bad and almost impossible to read. So I was wondering if there's a better way of doing that.







      json haskell aeson






      share|improve this question















      share|improve this question













      share|improve this question




      share|improve this question








      edited Nov 11 at 19:54









      Mark Seemann

      181k33323554




      181k33323554










      asked Nov 11 at 18:38









      atis

      504




      504






















          1 Answer
          1






          active

          oldest

          votes

















          up vote
          3
          down vote



          accepted










          Define the types you'd like to deserialise into, for example:



          -# LANGUAGE DeriveGeneric #-
          module Q53251928 where

          import Data.Aeson
          import GHC.Generics

          data Item = Item ndbno :: String deriving (Eq, Show, Generic)
          instance FromJSON Item

          data FoodStuff = FoodStuff item :: [Item] deriving (Eq, Show, Generic)
          instance FromJSON FoodStuff

          data RootJSON = RootJSON list :: FoodStuff deriving (Eq, Show, Generic)
          instance FromJSON RootJSON


          These types are the minimal types you'll need to access all the ndbno values. You can add other labels to the types to capture other data, e.g. group, start, end, etc.



          I downloaded the file in the link and attempted to decode it from GHCi, which worked fine:



          *Q53251928 Q53251928> decodeFileStrict "download.json" :: IO (Maybe RootJSON)
          Just (RootJSON list = FoodStuff item = [Item ndbno = "45044170",
          Item ndbno = "45044169",Item ndbno = "45287938",Item ndbno = "45314045",
          Item ndbno = "45036851",Item ndbno = "45036824",Item ndbno = "45198766",
          Item ndbno = "45270526",Item ndbno = "45270516",Item ndbno = "45374956",
          Item ndbno = "45215370",Item ndbno = "45225694",Item ndbno = "45225696",
          Item ndbno = "45217133",Item ndbno = "45053881",Item ndbno = "45270521",
          Item ndbno = "45226407",Item ndbno = "45218344",Item ndbno = "45225703",
          Item ndbno = "45335760",Item ndbno = "45221588",Item ndbno = "45193027",
          Item ndbno = "45194338",Item ndbno = "45194331",Item ndbno = "45256801"])





          share|improve this answer






















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            1 Answer
            1






            active

            oldest

            votes









            active

            oldest

            votes






            active

            oldest

            votes








            up vote
            3
            down vote



            accepted










            Define the types you'd like to deserialise into, for example:



            -# LANGUAGE DeriveGeneric #-
            module Q53251928 where

            import Data.Aeson
            import GHC.Generics

            data Item = Item ndbno :: String deriving (Eq, Show, Generic)
            instance FromJSON Item

            data FoodStuff = FoodStuff item :: [Item] deriving (Eq, Show, Generic)
            instance FromJSON FoodStuff

            data RootJSON = RootJSON list :: FoodStuff deriving (Eq, Show, Generic)
            instance FromJSON RootJSON


            These types are the minimal types you'll need to access all the ndbno values. You can add other labels to the types to capture other data, e.g. group, start, end, etc.



            I downloaded the file in the link and attempted to decode it from GHCi, which worked fine:



            *Q53251928 Q53251928> decodeFileStrict "download.json" :: IO (Maybe RootJSON)
            Just (RootJSON list = FoodStuff item = [Item ndbno = "45044170",
            Item ndbno = "45044169",Item ndbno = "45287938",Item ndbno = "45314045",
            Item ndbno = "45036851",Item ndbno = "45036824",Item ndbno = "45198766",
            Item ndbno = "45270526",Item ndbno = "45270516",Item ndbno = "45374956",
            Item ndbno = "45215370",Item ndbno = "45225694",Item ndbno = "45225696",
            Item ndbno = "45217133",Item ndbno = "45053881",Item ndbno = "45270521",
            Item ndbno = "45226407",Item ndbno = "45218344",Item ndbno = "45225703",
            Item ndbno = "45335760",Item ndbno = "45221588",Item ndbno = "45193027",
            Item ndbno = "45194338",Item ndbno = "45194331",Item ndbno = "45256801"])





            share|improve this answer


























              up vote
              3
              down vote



              accepted










              Define the types you'd like to deserialise into, for example:



              -# LANGUAGE DeriveGeneric #-
              module Q53251928 where

              import Data.Aeson
              import GHC.Generics

              data Item = Item ndbno :: String deriving (Eq, Show, Generic)
              instance FromJSON Item

              data FoodStuff = FoodStuff item :: [Item] deriving (Eq, Show, Generic)
              instance FromJSON FoodStuff

              data RootJSON = RootJSON list :: FoodStuff deriving (Eq, Show, Generic)
              instance FromJSON RootJSON


              These types are the minimal types you'll need to access all the ndbno values. You can add other labels to the types to capture other data, e.g. group, start, end, etc.



              I downloaded the file in the link and attempted to decode it from GHCi, which worked fine:



              *Q53251928 Q53251928> decodeFileStrict "download.json" :: IO (Maybe RootJSON)
              Just (RootJSON list = FoodStuff item = [Item ndbno = "45044170",
              Item ndbno = "45044169",Item ndbno = "45287938",Item ndbno = "45314045",
              Item ndbno = "45036851",Item ndbno = "45036824",Item ndbno = "45198766",
              Item ndbno = "45270526",Item ndbno = "45270516",Item ndbno = "45374956",
              Item ndbno = "45215370",Item ndbno = "45225694",Item ndbno = "45225696",
              Item ndbno = "45217133",Item ndbno = "45053881",Item ndbno = "45270521",
              Item ndbno = "45226407",Item ndbno = "45218344",Item ndbno = "45225703",
              Item ndbno = "45335760",Item ndbno = "45221588",Item ndbno = "45193027",
              Item ndbno = "45194338",Item ndbno = "45194331",Item ndbno = "45256801"])





              share|improve this answer
























                up vote
                3
                down vote



                accepted







                up vote
                3
                down vote



                accepted






                Define the types you'd like to deserialise into, for example:



                -# LANGUAGE DeriveGeneric #-
                module Q53251928 where

                import Data.Aeson
                import GHC.Generics

                data Item = Item ndbno :: String deriving (Eq, Show, Generic)
                instance FromJSON Item

                data FoodStuff = FoodStuff item :: [Item] deriving (Eq, Show, Generic)
                instance FromJSON FoodStuff

                data RootJSON = RootJSON list :: FoodStuff deriving (Eq, Show, Generic)
                instance FromJSON RootJSON


                These types are the minimal types you'll need to access all the ndbno values. You can add other labels to the types to capture other data, e.g. group, start, end, etc.



                I downloaded the file in the link and attempted to decode it from GHCi, which worked fine:



                *Q53251928 Q53251928> decodeFileStrict "download.json" :: IO (Maybe RootJSON)
                Just (RootJSON list = FoodStuff item = [Item ndbno = "45044170",
                Item ndbno = "45044169",Item ndbno = "45287938",Item ndbno = "45314045",
                Item ndbno = "45036851",Item ndbno = "45036824",Item ndbno = "45198766",
                Item ndbno = "45270526",Item ndbno = "45270516",Item ndbno = "45374956",
                Item ndbno = "45215370",Item ndbno = "45225694",Item ndbno = "45225696",
                Item ndbno = "45217133",Item ndbno = "45053881",Item ndbno = "45270521",
                Item ndbno = "45226407",Item ndbno = "45218344",Item ndbno = "45225703",
                Item ndbno = "45335760",Item ndbno = "45221588",Item ndbno = "45193027",
                Item ndbno = "45194338",Item ndbno = "45194331",Item ndbno = "45256801"])





                share|improve this answer














                Define the types you'd like to deserialise into, for example:



                -# LANGUAGE DeriveGeneric #-
                module Q53251928 where

                import Data.Aeson
                import GHC.Generics

                data Item = Item ndbno :: String deriving (Eq, Show, Generic)
                instance FromJSON Item

                data FoodStuff = FoodStuff item :: [Item] deriving (Eq, Show, Generic)
                instance FromJSON FoodStuff

                data RootJSON = RootJSON list :: FoodStuff deriving (Eq, Show, Generic)
                instance FromJSON RootJSON


                These types are the minimal types you'll need to access all the ndbno values. You can add other labels to the types to capture other data, e.g. group, start, end, etc.



                I downloaded the file in the link and attempted to decode it from GHCi, which worked fine:



                *Q53251928 Q53251928> decodeFileStrict "download.json" :: IO (Maybe RootJSON)
                Just (RootJSON list = FoodStuff item = [Item ndbno = "45044170",
                Item ndbno = "45044169",Item ndbno = "45287938",Item ndbno = "45314045",
                Item ndbno = "45036851",Item ndbno = "45036824",Item ndbno = "45198766",
                Item ndbno = "45270526",Item ndbno = "45270516",Item ndbno = "45374956",
                Item ndbno = "45215370",Item ndbno = "45225694",Item ndbno = "45225696",
                Item ndbno = "45217133",Item ndbno = "45053881",Item ndbno = "45270521",
                Item ndbno = "45226407",Item ndbno = "45218344",Item ndbno = "45225703",
                Item ndbno = "45335760",Item ndbno = "45221588",Item ndbno = "45193027",
                Item ndbno = "45194338",Item ndbno = "45194331",Item ndbno = "45256801"])






                share|improve this answer














                share|improve this answer



                share|improve this answer








                edited Nov 11 at 20:11

























                answered Nov 11 at 19:52









                Mark Seemann

                181k33323554




                181k33323554



























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