:PROPERTIES: :ID: ce613120-bb95-4488-82dc-6f2fcc144884 :mtime: 20231023024015 :ctime: 20231023024009 :END: #+title: list map #+filetags: :public:project: * Definition In the context of [[id:2dbb5e8a-32bf-49aa-ba92-9a98fe41c2fc][Functional Programming]], the *list map* function applies a function to each element of a list * Uses of List Map List map is very useful. You can use list map to implement [[id:bb1b3c8e-37fc-4121-b826-a221fd44dd79][matrix transpose.]] #+BEGIN_SRC ocaml let rec transpose = function | [] :: _ -> [] | rows -> (List.map List.hd rows) :: (transpose (List.map List.tl rows)) #+END_SRC * List Map in [[id:8952459c-5076-4e68-8a68-5f658209f39e][Ocaml]] #+BEGIN_SRC ocaml let rec map f = function | [] -> [] | x :: xs -> (f x) :: map f xs #+END_SRC #+RESULTS: : <fun> #+BEGIN_SRC ocaml :exports both map ((^) "hello ") ["John" ; "James"] #+END_SRC #+RESULTS: | hello John | hello James | * List Map in Haskell