How to convert an integer to a string in Erlang?

Question

I know strings in Erlang can be costly to use. So how do I convert \"5\"to 5?

Is there anything like io:format(\"~p\",[5]) tha

Answer 1

The following is probably not the neatest way, but it works:

1> lists:flatten(io_lib:format("~p", [35365])).
"35365"

EDIT: I've found that the following function comes in useful:

%% string_format/2
%% Like io:format except it returns the evaluated string rather than write
%% it to standard output.
%% Parameters:
%%   1. format string similar to that used by io:format.
%%   2. list of values to supply to format string.
%% Returns:
%%   Formatted string.
string_format(Pattern, Values) ->
    lists:flatten(io_lib:format(Pattern, Values)).

EDIT 2 (in response to comments): the above function came from a small program I wrote a while back to learn Erlang. I was looking for a string-formatting function and found the behaviour of io_lib:format/2 within erl counter-intuitive, for example:

1> io_lib:format("2 + 2 = ~p", [2+2]).
[50,32,43,32,50,32,61,32,"4"]

At the time, I was unaware of the 'auto-flattening' behaviour of output devices mentioned by @archaelus and so concluded that the above behaviour wasn't what I wanted.

This evening, I went back to this program and replaced calls to the string_format function above with io_lib:format. The only problems this caused were a few EUnit tests that failed because they were expecting a flattened string. These were easily fixed.

I agree with @gleber and @womble that using this function is overkill for converting an integer to a string. If that's all you need, use integer_to_list/1. KISS!