gistfile1.erl

install(Word,none) ->
    {Word,1,none,none};
install(Word,Tree) when Word<element(1,Tree) ->
    {OtherWord,Count,Left,Right}=Tree,
     {
       OtherWord,
       Count,
       install(Word,Left),
       Right
     };
install(Word,Tree) when Word>element(1,Tree) ->
    {OtherWord,Count,Left,Right}=Tree,

     {
       OtherWord,
       Count,
       Left,
      install(Word,Right)
     };
install(Word,Tree) when Word =:= element(1,Tree) ->
    {_,Count,Left,Right}=Tree,

    {
      Word,
      Count+1,
      Left,
      Right
    }
    .