Erlang 中类型转换

文档中给出的数据转换例子 罗列如下

源地址： http://www.erlang.org/doc/reference_manual/data_types.html

atom_to_list(hello)
"hello"
list_to_atom("hello").
hello
binary_to_list(<<"hello">>).
"hello"
binary_to_list(<<104,101,108,108,111>>).
"hello"
list_to_binary("hello").
<<104,101,108,108,111>>
integer_to_list(77).
"77"
list_to_integer("77").
77
tuple_to_list({a,b,c}).
[a,b,c]
list_to_tuple([a,b,c]).
{a,b,c}
term_to_binary({a,b,c}).
<<131,104,3,100,0,1,97,100,0,1,98,100,0,1,99>>
binary_to_term(<<131,104,3,100,0,1,97,100,0,1,98,100,0,1,99>>).
{a,b,c}

重点看一下 float_to_list/1

float_to_list(7.0).
"7.00000000000000000000e+00"
list_to_float("7.000e+00").
7.0
19> float_to_list(7.12, [{decimals, 4}]).
"7.1200"
20> float_to_list(7.12).
"7.12000000000000010658e+00"
21> float_to_list(7.12,[compact]).
"7.12000000000000010658e+00"
22> float_to_list(7.12, [{decimals, 6},compact]).
"7.12"
23> float_to_list(7.1234567, [{decimals, 6},compact]).
"7.123457"
24> float_to_list(7.12345, [{decima
ls, 6},compact]).
"7.12345

常用

%%--------------------------------------------------------------------
%% @doc
%% Converts to list
%% @end
%%--------------------------------------------------------------------
any_to_list(undefined) ->
    "";
any_to_list(List) when is_list(List) ->
    List;
any_to_list(Bin) when is_binary(Bin) ->
    case unicode:characters_to_binary(Bin, utf8, utf8) of
        Bin -> unicode:characters_to_list(Bin);
        _ -> binary_to_list(Bin)
    end;
any_to_list(Atom) when is_atom(Atom) ->
    atom_to_list(Atom);
any_to_list(Number) when is_integer(Number) ->
    integer_to_list(Number);
any_to_list(_) ->
    throw(badarg).
%%--------------------------------------------------------------------
%% @doc
%% Converts to atom
%% @end
%%--------------------------------------------------------------------
any_to_atom(Atom) when is_atom(Atom) ->
    Atom;
any_to_atom(List) when is_list(List) ->
    list_to_atom(List);
any_to_atom(Bin) when is_binary(Bin) ->
    list_to_atom(any_to_list(Bin));
any_to_atom(_) ->
    throw(badarg).
%%--------------------------------------------------------------------
%% @doc
%% Converts to binary
%% @end
%%--------------------------------------------------------------------
any_to_binary(Bin) when is_binary(Bin)->
    Bin;
any_to_binary(List) when is_list(List) ->
    case unicode:characters_to_binary(List) of
        {error,_,_} -> list_to_binary(List);
        B -> case unicode:characters_to_list(B,utf8) of
                 List -> B;
                 _ -> list_to_binary(List)
             end
    end;
any_to_binary(Atom) when is_atom(Atom) ->
    erlang:atom_to_binary(Atom, utf8);
any_to_binary(_) ->
    throw(badarg).
%%--------------------------------------------------------------------
%% @doc
%% convert to integer
%% @spec
%% @end
%%--------------------------------------------------------------------
any_to_integer(Int) when is_integer(Int) ->
    Int;
any_to_integer(List) when is_list(List) ->
    list_to_integer(List);
any_to_integer(Bin) when is_binary(Bin) ->
    list_to_integer(any_to_list(Bin));
any_to_integer(Float) when is_float(Float) ->
    trunc(Float);  %%round(Float);
any_to_integer(_) ->
    throw(badarg).