Elm - Handling the Basics(Conditionals, Records, Functions, Pattern Matching)

Seven More Languages
in Seven Weeks

開発環境

• OS X El Capitan - Apple (OS)
• Emacs (Text Editor)
• Elm (プログラミング言語)

Seven More Languages in Seven Weeks (Bruce Tate (著)、Ian Dees (著)、Frederic Daoud (著)、Jack Moffitt (著)、Pragmatic Bookshelf)のChapter 3(Elm)、Day 1(Handling the Basics)、Do (Easy)(No. 3034).を取り組んでみる。

Do (Easy)(No. 3034)

入出力結果(Emacs, Terminal, elm repl)

$ elm-repl 
---- elm repl 0.16.0 -----------------------------------------------------------
 :help for help, :exit to exit, more at <https://github.com/elm-lang/elm-repl>
--------------------------------------------------------------------------------
> product list = case list of \
|   [] -> 1 \
|   head::tail -> head * product tail
<function> : List number -> number
> product [1..10]
3628800 : number
> xFields points = case points of \
|   [] -> [] \
|   head::tail -> head.x::xFields tail
<function> : List { b | x : a } -> List a
> xFields [{x=5, y=0}, {x=1, y=0}, {x=4, y=0}, {x=2, y=0}, {x=3, y=0}]
[5,1,4,2,3] : List number
> person = {name="elm", age=10, address={country="Japan", state="Tokyo"}}
{ name = "elm", age = 10, address = { country = "Japan", state = "Tokyo" } }
    : { address : { country : String, state : String }
      , age : number
      , name : String
      }
> person
{ name = "elm", age = 10, address = { country = "Japan", state = "Tokyo" } }
    : { address : { country : String, state : String }
      , age : number
      , name : String
      }
> person.name
"elm" : String
> person.address
{ country = "Japan", state = "Tokyo" } : { country : String, state : String }
> person.address.country
"Japan" : String
> person.address.state
"Tokyo" : String
> :exit
$