2 Character Set and Source File Encoding

2.1 Character Set

In Erlang 4.8/OTP R5A the syntax of Erlang tokens was extended to allow the use of the full ISO-8859-1 (Latin-1) character set. This is noticeable in the following ways:

All the Latin-1 printable characters can be used and are shown without the escape backslash convention.
Atoms and variables can use all Latin-1 letters.

Octal	Decimal		Class
200 - 237	128 - 159		Control characters
240 - 277	160 - 191	- ¿	Punctuation characters
300 - 326	192 - 214	À - Ö	Uppercase letters
327	215	×	Punctuation character
330 - 336	216 - 222	Ø - Þ	Uppercase letters
337 - 366	223 - 246	ß - ö	Lowercase letters
367	247	÷	Punctuation character
370 - 377	248 - 255	ø - ÿ	Lowercase letters

Table 2.1: Character Classes.

In Erlang/OTP R16B the syntax of Erlang tokens was extended to handle Unicode. To begin with the support is limited to strings, but Erlang/OTP 18 is expected to handle Unicode atoms as well. More about the usage of Unicode in Erlang source files can be found in STDLIB's User's Guide.

2.2 Source File Encoding

The Erlang source file encoding is selected by a comment in one of the first two lines of the source file. The first string that matches the regular expression coding\s*[:=]\s*([-a-zA-Z0-9])+ selects the encoding. If the matching string is not a valid encoding it is ignored. The valid encodings are Latin-1 and UTF-8 where the case of the characters can be chosen freely.

The following example selects UTF-8 as default encoding:

%% coding: utf-8

Two more examples, both selecting Latin-1 as default encoding:

%% For this file we have chosen encoding = Latin-1

%% -*- coding: latin-1 -*-

The default encoding for Erlang source files was changed from Latin-1 to UTF-8 in Erlang OTP 17.0.