Today’s Erlang Thursday covers erlang:list_to_atom/1.

erlang:list_to_atom/1 takes a string, and returns an Erlang atom.

list_to_atom("foo").
% foo
list_to_atom("Foo").
% 'Foo'
list_to_atom("Foo_bar").
% 'Foo_bar'
list_to_atom("foo_bar").
% foo_bar
list_to_atom("foo"++"bar").
% foobar
list_to_atom("Erlang").
% 'Erlang'
list_to_atom("Elixir").
% 'Elixir'

This can be useful if you are having to create keys or identifiers based off strings read in from outside the system, such as parsing a CSV style header.

lists:map(fun erlang:list_to_atom/1,
          string:tokens("firstName,lastName,age,gender,preferredName,dateOfBirth", ",")).
% [firstName,lastName,age,gender,preferredName,dateOfBirth]

You do need to be careful when using erlang:list_to_atom/1 on strings acquired from the outside world of your program, as it only handles strings with character values under 256. But any character value¹ under 256 is fair game to be turned into an atom.

list_to_atom("Joe, Mike, and Robert").
% 'Joe, Mike, and Robert'
list_to_atom("it's").
% 'it's'
list_to_atom("heyn").
% 'heyn'€
list_to_atom("with_supported_char"++[255]).
% with_supported_charÿ
list_to_atom("with_non_supported_char"++[256]).
% ** exception error: bad argument
%      in function  list_to_atom/1
%         called as list_to_atom([119,105,116,104,95,110,111,110,95,115,117,112,112,111,114,
%                                 116,101,100,95,99,104,97,114,256])

–Proctor

1. Remember that character values are non-negative integer values as well. 0-255 inclusive. back