Erlang Reference Manual

User's Guide

Version 9.3

- User's Guide
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### Chapters

- Introduction
  - Top of chapter
  - Purpose
  - Prerequisites
  - Document Conventions
  - Complete List of BIFs
  - Reserved Words
- Character Set and Source File Encoding
  - Top of chapter
  - Character Set
  - Source File Encoding
- Data Types
  - Top of chapter
  - Terms
  - Number
  - Atom
  - Bit Strings and Binaries
  - Reference
  - Fun
  - Port Identifier
  - Pid
  - Tuple
  - Map
  - List
  - String
  - Record
  - Boolean
  - Escape Sequences
  - Type Conversions
- Pattern Matching
  - Top of chapter
  - Pattern Matching
- Modules
  - Top of chapter
  - Module Syntax
  - Module Attributes
  - Comments
  - module_info/0 and module_info/1 functions
- Functions
  - Top of chapter
  - Function Declaration Syntax
  - Function Evaluation
  - Tail recursion
  - Built-In Functions (BIFs)
- Types and Function Specifications
  - Top of chapter
  - The Erlang Type Language
  - Types and their Syntax
  - Type Declarations of User-Defined Types
  - Type Information in Record Declarations
  - Specifications for Functions
- Expressions
  - Top of chapter
  - Expression Evaluation
  - Terms
  - Variables
  - Patterns
  - Match
  - Function Calls
  - If
  - Case
  - Send
  - Receive
  - Term Comparisons
  - Arithmetic Expressions
  - Boolean Expressions
  - Short-Circuit Expressions
  - List Operations
  - Map Expressions
  - Bit Syntax Expressions
  - Fun Expressions
  - Catch and Throw
  - Try
  - Parenthesized Expressions
  - Block Expressions
  - List Comprehensions
  - Bit String Comprehensions
  - Guard Sequences
  - Operator Precedence
- Preprocessor
  - Top of chapter
  - File Inclusion
  - Defining and Using Macros
  - Predefined Macros
  - Macros Overloading
  - Flow Control in Macros
  - -error() and -warning() directives
  - Stringifying Macro Arguments
- Records
  - Top of chapter
  - Defining Records
  - Creating Records
  - Accessing Record Fields
  - Updating Records
  - Records in Guards
  - Records in Patterns
  - Nested Records
  - Internal Representation of Records
- Errors and Error Handling
  - Top of chapter
  - Terminology
  - Exceptions
  - Handling of Run-time Errors in Erlang
  - Exit Reasons
- Processes
  - Top of chapter
  - Processes
  - Process Creation
  - Registered Processes
  - Process Termination
  - Message Sending
  - Links
  - Error Handling
  - Monitors
  - Process Dictionary
- Distributed Erlang
  - Top of chapter
  - Distributed Erlang System
  - Nodes
  - Node Connections
  - epmd
  - Hidden Nodes
  - C Nodes
  - Security
  - Distribution BIFs
  - Distribution Command-Line Flags
  - Distribution Modules
- Compilation and Code Loading
  - Top of chapter
  - Compilation
  - Code Loading
  - Code Replacement
  - Running a Function When a Module is Loaded
- Ports and Port Drivers
  - Top of chapter
  - Ports
  - Port Drivers
  - Port BIFs

# 2 Character Set and Source File Encoding

### 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.

### 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.