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Maps

Access

Remove an entry from a map

Given a map pets {joe:cat,mary:turtle,bill:canary} remove the mapping for "bill" and print "canary"

clojure

; Maps are immutable
; The following expression will return a new map without the 'bill key
(let [pets '{joe cat mary turtle bill canary}]
(println (get pets 'bill))
(dissoc pets 'bill))

cpp C++/CLI .NET 2.0

if (pets->ContainsKey("bill"))
{
String^ value = safe_cast<String^>(pets["bill"]); pets->Remove("bill");
Console::WriteLine("{0}", value);
}

erlang

Pet = dict:fetch(bill, Pets0), Pets1 = dict:erase(bill, Pets0), io:format("~w~n", [Pet]),

erlang

Pet = ets:lookup_element(Pets, bill, 2), ets:delete(Pets, bill), io:format("~w~n", [Pet]),

erlang

{value, Pet} = gb_trees:lookup(bill, Pets0), Pets1 = gb_trees:delete(bill, Pets0), io:format("~w~n", [Pet]),

fantom

pet := map.remove("bill")
echo ("pet=$pet")

fsharp

let key = "bill"
match (pets |> Map.tryFind key) with
| Some(value) -> pets <- (Map.remove key pets) ; printfn "%s : %s removed" key value
| None -> printfn "Key %s not found" key

fsharp

let key = "bill"
let entry = if (pets.ContainsKey(key)) then Some(pets.[key]) ; else None
pets.Remove(key)

match entry with
| Some(value) -> printfn "%s" value
| None -> printfn "key not found"

go 1+

fmt.Println(pets["bill"])
delete(pets, "bill")

go 0.x

fmt.Println(pets["bill"])
pets["bill"] = "", false

groovy

pets = [joe:'cat', mary:'turtle', bill:'canary']
println pets.remove('bill')

haskell

import qualified Data.Map as M

main = do
let pets = M.fromList [("joe", "cat"), ("mary", "turtle"), ("bill", "canary")]
pets2 = M.delete "bill" pets
print $ maybe "" id (M.lookup "bill" pets)
print pets2

java

System.out.println(pets.remove("bill"))

ocaml

module StringMap = Map.Make (String)

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

let get_and_rem key m =
try
let value = StringMap.find key m in
let rm = StringMap.remove key m in
Some (value, rm)
with Not_found ->
None

let () =
let key = "bill" in
match get_and_rem key pets with
| Some (found, new_pets) ->
Printf.printf "%s : %s removed\n" key found
| None ->
Printf.printf "Key %s not found" key

ocaml

let get_and_rem m key =
try
let value = Hashtbl.find m key in
Hashtbl.remove m key;
Some value
with Not_found ->
None

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

let key = "bill" in
match get_and_rem pets key with
| Some found ->
Printf.printf "%s : %s removed\n" key found
| None ->
Printf.printf "Key %s not found" key

perl

print delete $pets{bill};

php

$last = array_pop($pets); // removes last key and assign it to the variable
echo $last;

php

$last = $pets[count($pets)-1];
echo $last;
unset($last);

php

$bill = $pets["bill"];
echo $bill;
unset($bill);

php

print_r(array_pop($pets));

python

print pets.pop('bill')

ruby

puts map.delete :bill

scala

val pet = pets("bill") ; pets -= "bill" ; println(pet)

scala

println(pets.removeKey("bill") match { case Some(pet) => pet ; case None => "***" })

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