Json.Decode example

keyValuePairs.elm

import Graphics.Element exposing (Element, show)
import Task exposing (Task, andThen)
import Json.Decode exposing (Decoder, int, string, object3, (:=), at, keyValuePairs)

import Http

type alias Languages =
  List (String, Int)

mailbox =
  Signal.mailbox []


-- VIEW

main : Signal Element
main =
  Signal.map show mailbox.signal


-- TASK

fetchApi =
  Http.get decoder api 

handleResponse data =
  Signal.send mailbox.address data

decoder : Decoder (List (String, Int))
decoder =
  keyValuePairs int

port run : Task Http.Error ()
port run =
  fetchApi `andThen` handleResponse

api =
  "https://api.github.com/repos/elm-lang/elm-lang.org/languages"

listDecoder.elm

import Graphics.Element exposing (Element, show)
import Task exposing (Task, andThen)
import Json.Decode exposing (Decoder, int, string, list, at, (:=), object1)
import Dict exposing (Dict)

import Http

mailbox =
  Signal.mailbox []

-- VIEW

main : Signal Element
main =
  Signal.map show mailbox.signal


-- TASK

fetchApi =
  Http.get decoder api 

handleResponse data =
  Signal.send mailbox.address data

fullNameDecoder : Decoder String
fullNameDecoder =
  object1 identity ("full_name" := string)
  
decoder =
  at ["items"] (list fullNameDecoder)

port run : Task Http.Error ()
port run =
  fetchApi `andThen` handleResponse

api =
  "https://api.github.com/search/repositories?q=language:elm&sort=starts&language=elm"

repoRecord.elm

import Graphics.Element exposing (Element, show)
import Task exposing (Task, andThen)
import Json.Decode exposing (Decoder, int, string, object3, (:=))

import Http

type alias RepoRecord =
  { name : String
  , description : String
  , watchers_count : Int
  }

mailbox =
  Signal.mailbox (RepoRecord "" "" 0)


-- VIEW

main : Signal Element
main =
  Signal.map show mailbox.signal


-- TASK

fetchApi =
  Http.get repoRecordDecoder api 

handleResponse data =
  Signal.send mailbox.address data

repoRecordDecoder : Decoder RepoRecord
repoRecordDecoder =
    object3 RepoRecord
        ("name" := string)
        ("description" := string)
        ("watchers_count" := int)

port run : Task Http.Error ()
port run =
  fetchApi `andThen` handleResponse

api =
  "https://api.github.com/repos/elm-lang/core"

repoTuple.elm

import Graphics.Element exposing (Element, show)
import Task exposing (Task, andThen)
import Json.Decode exposing (Decoder, int, string, object3, (:=))

import Http

type alias RepoTuple = ( String, String, Int )

mailbox =
  Signal.mailbox ("", "", 0)


-- VIEW

main : Signal Element
main =
  Signal.map show mailbox.signal


-- TASK

fetchApi =
  Http.get repoTupleDecoder api 

handleResponse data =
  Signal.send mailbox.address data

-- decoder changes depends on our data type
repoTupleDecoder : Decoder RepoTuple
repoTupleDecoder =
    object3 (,,)
        ("name" := string)
        ("description" := string)
        ("watchers_count" := int)

port run : Task Http.Error ()
port run =
  fetchApi `andThen` handleResponse

api =
  "https://api.github.com/repos/elm-lang/core"

whats your elm-package look like?

what version of elm are you running?