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<  Erlang  ~  searching for an item in a list
ishmael
Posted: Tue Aug 05, 2008 9:07 am Reply with quote
Joined: 23 Jul 2008 Posts: 9 Location: RSA
Hi,

I have a list of tuples I want to search.
I want the module to search the list for a name and return the related phone number or not_found, can anybody help?
Code:
-module(search).
-export([find_phone/2]).

 
 find_phone([{Name, Phone}|_], Name) ->
      {found,Phone};
 find_phone([_|T], Name) ->
      {T, Phone}.
 find_phone([], Name) ->
    not_found.
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Mazen
Posted: Tue Aug 05, 2008 11:01 am Reply with quote
User Joined: 20 Jul 2006 Posts: 164 Location: London
Hi Ishmael,

I suggest you take a look at lists:keysearch/3, it will do the work for you and you don't have to create a function for it (unless you want to wrap the response to return something else as I suspect you want in your case)

Here is the link:
http://www.erlang.org/doc/man/lists.html

Code:

find_phone(List, Name) ->
    %% E.g.
    %% List = [{"Mazen","555-123456"} | ...],
    %% Name = "Mazen",
    case lists:keysearch(Name, 1, List) of
        {value, {Name,Phonenumber}} ->
            {found, Phonenumber};
        false ->
            not_found
    end.


/Mazen
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dsmith
Posted: Mon Aug 11, 2008 2:20 am Reply with quote
User Joined: 08 Aug 2007 Posts: 41 Location: Toronto
Ishmael,

Use Mazen suggestion in practise, but this is the code you were trying for ...

Code:

-module(search).
-export([find_phone/2]).
 
 find_phone([], _) ->
    not_found;
 find_phone([{Name, Phone}|_], Name) ->
      {found,Phone};
 find_phone([_|T], Name) ->
      find_phone(T, Name).

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