Erlang -- Character Set and Source File Encoding

# 2 Character Set and Source File Encoding

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2.1 Character Set

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.

- 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. The support was limited to string literals and comments. More about the usage of Unicode in Erlang source files can be found in STDLIB's User's Guide.

From Erlang/OTP 20, atoms and function names are also allowed to contain Unicode characters outside the ISO-Latin-1 range. Module names, application names, and node names are still restricted to the ISO-Latin-1 range.

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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 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 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 is changed from Latin-1 to UTF-8 since Erlang/OTP 17.0.