用Erlang实现二分查找算法

算法实现如下

-module(bisearch).
-export([start/2]).

start(Value,List) ->
    Len = length(List),
    FirstValue = lists:nth(1, List),
    LastValue = lists:nth(Len, List),
    if FirstValue =:= Value orelse LastValue =:= Value ->
            io:format("found ~w~n", [Value]);  % 查找值在列表的首尾
        true ->
            Result = calu(1, length(List), Value, List),
            case Result of
                found -> io:format("found ~w~n", [Value]);
                _ -> io:format("not found ~w~n", [Value])
            end
    end.

%% 二分查找
calu(L, H, Value, List) ->
    M = (L+H) div 2,
    case L =:= M of
        true -> none;  % 查找范围段只有两个元素，结束查找
        false ->
            MValue = lists:nth(M, List), % 计算中值
            if
                Value =:= MValue ->
                    found;               % 查找成功
                Value < MValue ->
                    calu(L, M, Value, List); % 设置列表的前段为新的查找范围
                Value > MValue ->
                    calu(M, H, Value, List)  % 设置列表的后段为新的查找范围
            end
    end.