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Maps

Access

Retrieve a value from a map

Given a map pets {joe:cat,mary:turtle,bill:canary} print the pet for "joe" ("cat")

clojure

(def pets '{joe cat mary turtle bill canary})

(println (get pets 'joe))

cpp C++/CLI .NET 2.0

if (pets->ContainsKey("joe")) Console::WriteLine(pets["joe"]);

cpp

cout << pets["joe"] << endl;

erlang

dict:is_key(joe, Pets) andalso begin io:format("~w~n", [dict:fetch(joe, Pets)]), true end.

erlang

case dict:find(joe, Pets) of error -> false ; {ok, Pet} -> io:format("~w~n", [Pet]) end.

erlang

IsMember = ets:member(Pets, joe), if (IsMember) -> io:format("~w~n", [ets:lookup_element(Pets, joe, 2)]) ; true -> false end.

erlang

case ets:match(Pets, {joe, '$1'}) of [] -> false ; [[Pet]] -> io:format("~w~n", [Pet]) end.

erlang

case gb_trees:lookup(joe, Pets) of none -> false ; {value, Pet} -> io:format("~w~n", [Pet]) end.

fantom

map := ["joe":"cat", "mary":"turtle", "bill":"canary"]
pet := map["joe"]
echo("pet=$pet")

fsharp

if (Map.mem "joe" pets) then printfn "%s" (Map.find "joe" pets)

fsharp

if (pets |> Map.exists (fun key _ -> key = "joe")) then printfn "%s" (Map.find "joe" pets)

fsharp

let key = "joe"
match (pets |> Map.tryfind key) with
| Some(value) -> printfn "%s" value
| None -> printfn "Key %s not found" key

fsharp

if pets.ContainsKey("joe") then printfn "%s" pets.["joe"]

fsharp

if pets.ContainsKey("joe") then printfn "%s" (pets.["joe"] :?> string)

fmt.Println(pets["joe"])

groovy

pets = [joe:'cat', mary:'turtle', bill:'canary']
assert pets['joe'] == 'cat'

groovy

assert pets.joe == 'cat'

haskell

import qualified Data.Map as M

pets = M.fromList [("joe", "cat"), ("mary", "turtle"), ("bill", "canary")]
retrieve = print $ M.findWithDefault "Not found" "joe" pets

java

String pet = pets.get("joe");

ocaml

module StringMap = Map.Make (String)

let map =
List.fold_left (fun map (key, value) ->
StringMap.add key value map
) StringMap.empty [("joe", "cat"); ("mary", "turtle"); ("bill", "canary")]

let () =
try
let pet = StringMap.find "joe" map in
Printf.printf "Joe's pet is a %s.\n" pet
with Not_found ->
prerr_endline "No pet found for Joe."

ocaml

let () =
let map = Hashtbl.create 42 in
List.iter (fun (key, value) ->
Hashtbl.add map key value
) [("joe", "cat"); ("mary", "turtle"); ("bill", "canary")];

try
let pet = Hashtbl.find map "joe" in
Printf.printf "Joe's pet is a %s.\n" pet
with Not_found ->
prerr_endline "No pet found for Joe."

perl

%pets = (joe => 'cat', mary => 'turtle', bill=>'canary');
print $pets{joe};

php

echo $pets["joe"];

python

print pets['joe']

ruby

puts map['joe']

scala

if (pets.contains("joe")) println(pets("joe"))

scala

println(pets.getOrElse("joe", "*** no pet owned ***"))

scala

pets("joe")

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