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<  Erlang  ~  Using keyfind
klm
Posted: Sat May 23, 2009 9:11 pm Reply with quote
User Joined: 11 May 2009 Posts: 18
Hello !

I'm trying to use the function keyfind but I don't understand how does it works.


Indeed I've done a record

(new_player is a personnal function to create a new player)

Player1= new_player(1,{192,168,1,10},"nameone"},
Player2 = new_player(2,{192,168,1,10},"nametwo"},

List = [Player1,Player2],

My_tuple = lists:keyfind("nameone", 3, List),

io:format("Find the tuple ~w ~n",[My_tuple#player.num]).

and I've got this error :

** exception error: {badrecord,player}
in function test:new/0

Could you explain me how to use the function keyfind ?

thanks !

and if you know too how to do real random (seed() blocks the program) I'm interested Smile
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ates
Posted: Mon May 25, 2009 10:13 am Reply with quote
Joined: 23 May 2009 Posts: 3
I hope it help:

1> Player1 = {1, {1,2,3,4}, "player1"}.
{1,{1,2,3,4},"player1"}
2> Player2 = {2, {4,3,2,1}, "player2"}.
{2,{4,3,2,1},"player2"}
3> List = [Player1, Player2].
4> lists:keyfind("player2", 3, List).
{2,{4,3,2,1},"player2"}
5> rd(player, {id, ip, name}).
player
6> Tuple = lists:keyfind("player2", 3, List).
{2,{4,3,2,1},"player2"}
7> {ID, IP, Name} = Tuple.
{2,{4,3,2,1},"player2"}
8> Tuple2 = #player{id = ID, ip = IP, name = Name}.
#player{id = 2,ip = {4,3,2,1},name = "player2"}
9> io:format("Results: ~p~n", [Tuple2#player.id]).
Results: 2
ok
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uwiger
Posted: Mon May 25, 2009 10:24 am Reply with quote
User Joined: 03 Jul 2006 Posts: 604 Location: Sweden
klm wrote:
Indeed I've done a record

(new_player is a personnal function to create a new player)

Player1= new_player(1,{192,168,1,10},"nameone"},
Player2 = new_player(2,{192,168,1,10},"nametwo"},

List = [Player1,Player2],

My_tuple = lists:keyfind("nameone", 3, List),


You should really try the commands one by one in the shell, but the problem here is that a player record would have to have the atom 'player' as a first element. So printing out the records in question:

Player1 = {player,1,{192,168,1,10},"nameone"},
Player2 = {player,2,{192,168,1,10},"nametwo"},

Then using keyfind(), you'd have to search on the fourth element (including the tag), not the third.

Using record syntax, you can also write

lists:keyfind("nameone",#player.name,List).
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klm
Posted: Mon May 25, 2009 10:48 am Reply with quote
User Joined: 11 May 2009 Posts: 18
Yes thanks

I tried and it works, I did'nt found how it works in the man on erlang.org

It was easiest to use than I thought

Erlang is powerful but it's difficult after programming in C language or Java
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