2  Character Set and Source File Encoding

2 Character Set and Source File Encoding

The syntax of Erlang tokens 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.

  • Unquoted 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

The following tokens are allowed to also use Unicode characters outside of the Latin-1 range:

  • String literals. Example: "√π"

  • Character literals. Example: $∑

  • Comments in code.

  • Quoted atoms. Example: 'μs'

  • Function names. Example: 's_to_μs'(S) -> S * 1_000_000.

Atoms used as module names, application names, and node names are restricted to the Latin-1 range.


Support for Unicode in string literals, character literals, and comments was introduced in Erlang/OTP R16B. Support for Unicode in atom and function names was introduced in Erlang/OTP 20.

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 an invalid encoding, it is ignored. The valid encodings are Latin-1 and UTF-8, where the case of the characters can be chosen freely.

The default Erlang source file encoding if no valid coding comment is present is UTF-8.

Two examples, both selecting Latin-1 as the source file 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.