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elisp : Character Type
table of contents
Introduction
Coding Conventions
Lisp Data Types
Numbers
Strings and Characters
Lists
Sequences Arrays Vectors
Hash Tables
Symbols
Evaluation
Control Structures
Variables
Functions
Macros
Customization
Loading
Byte Compilation
Advising Functions
Debugging
Read and Print
Minibuffers
Command Loop
Keymaps
Modes
Documentation
Files
Backups and Auto-Saving
Buffers
Windows
Frames
Positions
Markers
Text
Non-ASCII Characters
Searching and Matching
Syntax Tables
Abbrevs
Processes
Display
Calendar
System Interface
Antinews
GNU Free Documentation License
GPL
Tips
GNU Emacs Internals
Standard Errors
Standard Buffer-Local Variables
Standard Keymaps
Standard Hooks
Index
New Symbols
Caveats
Lisp History
Conventions
Acknowledgements
Some Terms
nil and t
Evaluation Notation
Printing Notation
Error Messages
Buffer Text Notation
Format of Descriptions
Coding Conventions
Compilation Tips
Documentation Tips
Comment Tips
Library Headers
A Sample Function Description
A Sample Variable Description
Printed Representation
Comments
Programming Types
Editing Types
Type Predicates
Equality Predicates
Integer Type
Floating Point Type
Character Type
Sequence Type
Cons Cell Type
Array Type
String Type
Vector Type
Symbol Type
Function Type
Macro Type
Primitive Function Type
Byte-Code Type
Autoload Type
Dotted Pair Notation
Association List Type
Buffer Type
Window Type
Window Configuration Type
Marker Type
Process Type
Stream Type
Keymap Type
Overlay Type
Integer Basics
Float Basics
Predicates on Numbers
Comparison of Numbers
Arithmetic Operations
Bitwise Operations
Numeric Conversions
Math Functions
Random Numbers
String Basics
Predicates for Strings
Creating Strings
Text Comparison
String Conversion
Formatting Strings
Case Conversion
Cons Cells
Lists as Boxes
List-related Predicates
List Elements
Building Lists
Modifying Lists
Sets And Lists
Association Lists
Setcar
Setcdr
Rearrangement
Sequence Functions
Arrays
Array Functions
Vectors
Symbol Components
Definitions
Creating Symbols
Property Lists
Intro Eval
Eval
Forms
Quoting
Self-Evaluating Forms
Symbol Forms
Classifying Lists
Function Forms
Macro Forms
Special Forms
Autoloading
Sequencing
Conditionals
Combining Conditions
Iteration
Nonlocal Exits
Catch and Throw
Examples of Catch
Errors
Cleanups
Signaling Errors
Processing of Errors
Handling Errors
Error Symbols
Global Variables
Constant Variables
Local Variables
Void Variables
Defining Variables
Accessing Variables
Setting Variables
Variable Scoping
Buffer-Local Variables
Scope
Extent
Impl of Scope
Using Scoping
Intro to Buffer-Local
Creating Buffer-Local
Default Value
What Is a Function
Lambda Expressions
Function Names
Defining Functions
Calling Functions
Mapping Functions
Anonymous Functions
Function Cells
Related Topics
Lambda Components
Simple Lambda
Argument List
Function Documentation
Simple Macro
Expansion
Compiling Macros
Defining Macros
Backquote
Problems with Macros
How Programs Do Loading
Autoload
Named Features
Repeated Loading
Compilation Functions
Disassembly
Simple Advice
Defining Advice
Computed Advice
Activation of Advice
Enabling Advice
Preactivation
Argument Access in Advice
Subr Arguments
Combined Definition
Debugger
Syntax Errors
Compilation Errors
Edebug
Error Debugging
Function Debugging
Explicit Debug
Using Debugger
Debugger Commands
Invoking the Debugger
Internals of Debugger
Excess Open
Excess Close
Streams Intro
Input Streams
Input Functions
Output Streams
Output Functions
Intro to Minibuffers
Text from Minibuffer
Object from Minibuffer
Completion
Yes-or-No Queries
Minibuffer Misc
Basic Completion
Minibuffer Completion
Completion Commands
High-Level Completion
Reading File Names
Programmed Completion
Command Overview
Defining Commands
Interactive Call
Command Loop Info
Input Events
Reading Input
Waiting
Quitting
Prefix Command Arguments
Recursive Editing
Disabling Commands
Command History
Keyboard Macros
Using Interactive
Interactive Codes
Interactive Examples
Keymap Terminology
Format of Keymaps
Creating Keymaps
Inheritance and Keymaps
Prefix Keys
Menu Keymaps
Active Keymaps
Key Lookup
Functions for Key Lookup
Changing Key Bindings
Key Binding Commands
Scanning Keymaps
Major Modes
Minor Modes
Mode Line Format
Hooks
Major Mode Conventions
Example Major Modes
Auto Major Mode
Mode Help
Minor Mode Conventions
Keymaps and Minor Modes
Mode Line Data
Mode Line Variables
%-Constructs
Documentation Basics
Accessing Documentation
Keys in Documentation
Describing Characters
Help Functions
Visiting Files
Saving Buffers
Reading from Files
Writing to Files
File Locks
Information about Files
Contents of Directories
Changing Files
File Names
Visiting Functions
Subroutines of Visiting
Testing Accessibility
Kinds of Files
File Attributes
File Name Components
Directory Names
Relative File Names
File Name Expansion
Unique File Names
File Name Completion
Backup Files
Auto-Saving
Reverting
Making Backups
Rename or Copy
Numbered Backups
Backup Names
Buffer Basics
Buffer Names
Buffer File Name
Buffer Modification
Modification Time
Read Only Buffers
The Buffer List
Creating Buffers
Killing Buffers
Current Buffer
Basic Windows
Splitting Windows
Deleting Windows
Selecting Windows
Cyclic Window Ordering
Buffers and Windows
Displaying Buffers
Window Point
Window Start
Vertical Scrolling
Horizontal Scrolling
Size of Window
Resizing Windows
Window Configurations
Creating Frames
Multiple Displays
Frame Parameters
Frame Titles
Deleting Frames
Finding All Frames
Frames and Windows
Minibuffers and Frames
Input Focus
Visibility of Frames
Raising and Lowering
Frame Configurations
Mouse Tracking
Mouse Position
Pop-Up Menus
Dialog Boxes
Pointer Shapes
Window System Selections
Color Names
Resources
Display Feature Testing
Point
Motion
Excursions
Narrowing
Character Motion
Word Motion
Buffer End Motion
Text Lines
Screen Lines
List Motion
Skipping Characters
Overview of Markers
Predicates on Markers
Creating Markers
Information from Markers
Moving Markers
The Mark
The Region
Near Point
Buffer Contents
Insertion
Commands for Insertion
Deletion
User-Level Deletion
The Kill Ring
Undo
Auto Filling
Filling
Margins
Sorting
Indentation
Columns
Case Changes
Text Properties
Substitution
Transposition
Registers
Change Hooks
Kill Ring Concepts
Kill Functions
Yank Commands
Low-Level Kill Ring
Internals of Kill Ring
Primitive Indent
Mode-Specific Indent
Region Indent
Relative Indent
Indent Tabs
Motion by Indent
Examining Properties
Changing Properties
Property Search
Special Properties
Format Properties
Sticky Properties
Saving Properties
Lazy Properties
Clickable Text
Fields
Not Intervals
Text Representations
Converting Representations
Selecting a Representation
Character Codes
Character Sets
Chars and Bytes
Splitting Characters
Scanning Charsets
Translation of Characters
Coding Systems
Input Methods
Locales
String Search
Regular Expressions
Regexp Search
Match Data
Saving Match Data
Standard Regexps
Searching and Case
Syntax of Regexps
Regexp Example
Syntax Descriptors
Syntax Table Functions
Parsing Expressions
Standard Syntax Tables
Syntax Table Internals
Syntax Class Table
Syntax Flags
Abbrev Mode
Abbrev Tables
Defining Abbrevs
Abbrev Files
Abbrev Expansion
Standard Abbrev Tables
Subprocess Creation
Synchronous Processes
Asynchronous Processes
Deleting Processes
Process Information
Input to Processes
Signals to Processes
Output from Processes
Sentinels
Network
Process Buffers
Filter Functions
Accepting Output
Starting Up
Getting Out
System Environment
Terminal Input
Terminal Output
Flow Control
Batch Mode
Startup Summary
Init File
Terminal-Specific
Command-Line Arguments
Killing Emacs
Suspending Emacs
Refresh Screen
Truncation
The Echo Area
Selective Display
Overlay Arrow
Temporary Displays
Waiting
Blinking
Usual Display
Beeping
Window Systems
Building Emacs
Pure Storage
Garbage Collection
Object Internals
Writing Emacs Primitives
Buffer Internals
Window Internals
Process Internals
Character Type
--------------
A "character" in Emacs Lisp is nothing more than an integer. In
other words, characters are represented by their character codes. For
example, the character `A' is represented as the integer 65.
Individual characters are not often used in programs. It is far more
common to work with _strings_, which are sequences composed of
characters. *Note String Type::.
Characters in strings, buffers, and files are currently limited to
the range of 0 to 524287--nineteen bits. But not all values in that
range are valid character codes. Codes 0 through 127 are ASCII codes;
the rest are non-ASCII (*note Non-ASCII Characters::). Characters that
represent keyboard input have a much wider range, to encode modifier
keys such as Control, Meta and Shift.
Since characters are really integers, the printed representation of a
character is a decimal number. This is also a possible read syntax for
a character, but writing characters that way in Lisp programs is a very
bad idea. You should _always_ use the special read syntax formats that
Emacs Lisp provides for characters. These syntax formats start with a
question mark.
The usual read syntax for alphanumeric characters is a question mark
followed by the character; thus, `?A' for the character `A', `?B' for
the character `B', and `?a' for the character `a'.
For example:
?Q => 81 ?q => 113
You can use the same syntax for punctuation characters, but it is
often a good idea to add a `\' so that the Emacs commands for editing
Lisp code don't get confused. For example, `?\ ' is the way to write
the space character. If the character is `\', you _must_ use a second
`\' to quote it: `?\\'.
You can express the characters Control-g, backspace, tab, newline,
vertical tab, formfeed, return, del, and escape as `?\a', `?\b', `?\t',
`?\n', `?\v', `?\f', `?\r', `?\d', and `?\e', respectively. Thus,
?\a => 7 ; `C-g'
?\b => 8 ; backspace, , `C-h'
?\t => 9 ; tab, , `C-i'
?\n => 10 ; newline, `C-j'
?\v => 11 ; vertical tab, `C-k'
?\f => 12 ; formfeed character, `C-l'
?\r => 13 ; carriage return, , `C-m'
?\e => 27 ; escape character, , `C-['
?\\ => 92 ; backslash character, `\'
?\d => 127 ; delete character,
These sequences which start with backslash are also known as "escape
sequences", because backslash plays the role of an escape character;
this usage has nothing to do with the character .
Control characters may be represented using yet another read syntax.
This consists of a question mark followed by a backslash, caret, and the
corresponding non-control character, in either upper or lower case. For
example, both `?\^I' and `?\^i' are valid read syntax for the character
`C-i', the character whose value is 9.
Instead of the `^', you can use `C-'; thus, `?\C-i' is equivalent to
`?\^I' and to `?\^i':
?\^I => 9 ?\C-I => 9
In strings and buffers, the only control characters allowed are those
that exist in ASCII; but for keyboard input purposes, you can turn any
character into a control character with `C-'. The character codes for
these non-ASCII control characters include the 2**26 bit as well as the
code for the corresponding non-control character. Ordinary terminals
have no way of generating non-ASCII control characters, but you can
generate them straightforwardly using X and other window systems.
For historical reasons, Emacs treats the character as the
control equivalent of `?':
?\^? => 127 ?\C-? => 127
As a result, it is currently not possible to represent the character
`Control-?', which is a meaningful input character under X, using
`\C-'. It is not easy to change this, as various Lisp files refer to
in this way.
For representing control characters to be found in files or strings,
we recommend the `^' syntax; for control characters in keyboard input,
we prefer the `C-' syntax. Which one you use does not affect the
meaning of the program, but may guide the understanding of people who
read it.
A "meta character" is a character typed with the modifier
key. The integer that represents such a character has the 2**27 bit
set (which on most machines makes it a negative number). We use high
bits for this and other modifiers to make possible a wide range of
basic character codes.
In a string, the 2**7 bit attached to an ASCII character indicates a
meta character; thus, the meta characters that can fit in a string have
codes in the range from 128 to 255, and are the meta versions of the
ordinary ASCII characters. (In Emacs versions 18 and older, this
convention was used for characters outside of strings as well.)
The read syntax for meta characters uses `\M-'. For example,
`?\M-A' stands for `M-A'. You can use `\M-' together with octal
character codes (see below), with `\C-', or with any other syntax for a
character. Thus, you can write `M-A' as `?\M-A', or as `?\M-\101'.
Likewise, you can write `C-M-b' as `?\M-\C-b', `?\C-\M-b', or
`?\M-\002'.
The case of a graphic character is indicated by its character code;
for example, ASCII distinguishes between the characters `a' and `A'.
But ASCII has no way to represent whether a control character is upper
case or lower case. Emacs uses the 2**25 bit to indicate that the
shift key was used in typing a control character. This distinction is
possible only when you use X terminals or other special terminals;
ordinary terminals do not report the distinction to the computer in any
way. The Lisp syntax for the shift bit is `\S-'; thus, `?\C-\S-o' or
`?\C-\S-O' represents the shifted-control-o character.
The X Window System defines three other modifier bits that can be set
in a character: "hyper", "super" and "alt". The syntaxes for these
bits are `\H-', `\s-' and `\A-'. (Case is significant in these
prefixes.) Thus, `?\H-\M-\A-x' represents `Alt-Hyper-Meta-x'.
Numerically, the bit values are 2**22 for alt, 2**23 for super and
2**24 for hyper.
Finally, the most general read syntax for a character represents the
character code in either octal or hex. To use octal, write a question
mark followed by a backslash and the octal character code (up to three
octal digits); thus, `?\101' for the character `A', `?\001' for the
character `C-a', and `?\002' for the character `C-b'. Although this
syntax can represent any ASCII character, it is preferred only when the
precise octal value is more important than the ASCII representation.
?\012 => 10 ?\n => 10 ?\C-j => 10
?\101 => 65 ?A => 65
To use hex, write a question mark followed by a backslash, `x', and
the hexadecimal character code. You can use any number of hex digits,
so you can represent any character code in this way. Thus, `?\x41' for
the character `A', `?\x1' for the character `C-a', and `?\x8e0' for the
Latin-1 character `a' with grave accent.
A backslash is allowed, and harmless, preceding any character without
a special escape meaning; thus, `?\+' is equivalent to `?+'. There is
no reason to add a backslash before most characters. However, you
should add a backslash before any of the characters `()\|;'`"#.,' to
avoid confusing the Emacs commands for editing Lisp code. Also add a
backslash before whitespace characters such as space, tab, newline and
formfeed. However, it is cleaner to use one of the easily readable
escape sequences, such as `\t', instead of an actual whitespace
character such as a tab.
back to top
elisp : Character Type
table of contents
Introduction
Coding Conventions
Lisp Data Types
Numbers
Strings and Characters
Lists
Sequences Arrays Vectors
Hash Tables
Symbols
Evaluation
Control Structures
Variables
Functions
Macros
Customization
Loading
Byte Compilation
Advising Functions
Debugging
Read and Print
Minibuffers
Command Loop
Keymaps
Modes
Documentation
Files
Backups and Auto-Saving
Buffers
Windows
Frames
Positions
Markers
Text
Non-ASCII Characters
Searching and Matching
Syntax Tables
Abbrevs
Processes
Display
Calendar
System Interface
Antinews
GNU Free Documentation License
GPL
Tips
GNU Emacs Internals
Standard Errors
Standard Buffer-Local Variables
Standard Keymaps
Standard Hooks
Index
New Symbols
Caveats
Lisp History
Conventions
Acknowledgements
Some Terms
nil and t
Evaluation Notation
Printing Notation
Error Messages
Buffer Text Notation
Format of Descriptions
Coding Conventions
Compilation Tips
Documentation Tips
Comment Tips
Library Headers
A Sample Function Description
A Sample Variable Description
Printed Representation
Comments
Programming Types
Editing Types
Type Predicates
Equality Predicates
Integer Type
Floating Point Type
Character Type
Sequence Type
Cons Cell Type
Array Type
String Type
Vector Type
Symbol Type
Function Type
Macro Type
Primitive Function Type
Byte-Code Type
Autoload Type
Dotted Pair Notation
Association List Type
Buffer Type
Window Type
Window Configuration Type
Marker Type
Process Type
Stream Type
Keymap Type
Overlay Type
Integer Basics
Float Basics
Predicates on Numbers
Comparison of Numbers
Arithmetic Operations
Bitwise Operations
Numeric Conversions
Math Functions
Random Numbers
String Basics
Predicates for Strings
Creating Strings
Text Comparison
String Conversion
Formatting Strings
Case Conversion
Cons Cells
Lists as Boxes
List-related Predicates
List Elements
Building Lists
Modifying Lists
Sets And Lists
Association Lists
Setcar
Setcdr
Rearrangement
Sequence Functions
Arrays
Array Functions
Vectors
Symbol Components
Definitions
Creating Symbols
Property Lists
Intro Eval
Eval
Forms
Quoting
Self-Evaluating Forms
Symbol Forms
Classifying Lists
Function Forms
Macro Forms
Special Forms
Autoloading
Sequencing
Conditionals
Combining Conditions
Iteration
Nonlocal Exits
Catch and Throw
Examples of Catch
Errors
Cleanups
Signaling Errors
Processing of Errors
Handling Errors
Error Symbols
Global Variables
Constant Variables
Local Variables
Void Variables
Defining Variables
Accessing Variables
Setting Variables
Variable Scoping
Buffer-Local Variables
Scope
Extent
Impl of Scope
Using Scoping
Intro to Buffer-Local
Creating Buffer-Local
Default Value
What Is a Function
Lambda Expressions
Function Names
Defining Functions
Calling Functions
Mapping Functions
Anonymous Functions
Function Cells
Related Topics
Lambda Components
Simple Lambda
Argument List
Function Documentation
Simple Macro
Expansion
Compiling Macros
Defining Macros
Backquote
Problems with Macros
How Programs Do Loading
Autoload
Named Features
Repeated Loading
Compilation Functions
Disassembly
Simple Advice
Defining Advice
Computed Advice
Activation of Advice
Enabling Advice
Preactivation
Argument Access in Advice
Subr Arguments
Combined Definition
Debugger
Syntax Errors
Compilation Errors
Edebug
Error Debugging
Function Debugging
Explicit Debug
Using Debugger
Debugger Commands
Invoking the Debugger
Internals of Debugger
Excess Open
Excess Close
Streams Intro
Input Streams
Input Functions
Output Streams
Output Functions
Intro to Minibuffers
Text from Minibuffer
Object from Minibuffer
Completion
Yes-or-No Queries
Minibuffer Misc
Basic Completion
Minibuffer Completion
Completion Commands
High-Level Completion
Reading File Names
Programmed Completion
Command Overview
Defining Commands
Interactive Call
Command Loop Info
Input Events
Reading Input
Waiting
Quitting
Prefix Command Arguments
Recursive Editing
Disabling Commands
Command History
Keyboard Macros
Using Interactive
Interactive Codes
Interactive Examples
Keymap Terminology
Format of Keymaps
Creating Keymaps
Inheritance and Keymaps
Prefix Keys
Menu Keymaps
Active Keymaps
Key Lookup
Functions for Key Lookup
Changing Key Bindings
Key Binding Commands
Scanning Keymaps
Major Modes
Minor Modes
Mode Line Format
Hooks
Major Mode Conventions
Example Major Modes
Auto Major Mode
Mode Help
Minor Mode Conventions
Keymaps and Minor Modes
Mode Line Data
Mode Line Variables
%-Constructs
Documentation Basics
Accessing Documentation
Keys in Documentation
Describing Characters
Help Functions
Visiting Files
Saving Buffers
Reading from Files
Writing to Files
File Locks
Information about Files
Contents of Directories
Changing Files
File Names
Visiting Functions
Subroutines of Visiting
Testing Accessibility
Kinds of Files
File Attributes
File Name Components
Directory Names
Relative File Names
File Name Expansion
Unique File Names
File Name Completion
Backup Files
Auto-Saving
Reverting
Making Backups
Rename or Copy
Numbered Backups
Backup Names
Buffer Basics
Buffer Names
Buffer File Name
Buffer Modification
Modification Time
Read Only Buffers
The Buffer List
Creating Buffers
Killing Buffers
Current Buffer
Basic Windows
Splitting Windows
Deleting Windows
Selecting Windows
Cyclic Window Ordering
Buffers and Windows
Displaying Buffers
Window Point
Window Start
Vertical Scrolling
Horizontal Scrolling
Size of Window
Resizing Windows
Window Configurations
Creating Frames
Multiple Displays
Frame Parameters
Frame Titles
Deleting Frames
Finding All Frames
Frames and Windows
Minibuffers and Frames
Input Focus
Visibility of Frames
Raising and Lowering
Frame Configurations
Mouse Tracking
Mouse Position
Pop-Up Menus
Dialog Boxes
Pointer Shapes
Window System Selections
Color Names
Resources
Display Feature Testing
Point
Motion
Excursions
Narrowing
Character Motion
Word Motion
Buffer End Motion
Text Lines
Screen Lines
List Motion
Skipping Characters
Overview of Markers
Predicates on Markers
Creating Markers
Information from Markers
Moving Markers
The Mark
The Region
Near Point
Buffer Contents
Insertion
Commands for Insertion
Deletion
User-Level Deletion
The Kill Ring
Undo
Auto Filling
Filling
Margins
Sorting
Indentation
Columns
Case Changes
Text Properties
Substitution
Transposition
Registers
Change Hooks
Kill Ring Concepts
Kill Functions
Yank Commands
Low-Level Kill Ring
Internals of Kill Ring
Primitive Indent
Mode-Specific Indent
Region Indent
Relative Indent
Indent Tabs
Motion by Indent
Examining Properties
Changing Properties
Property Search
Special Properties
Format Properties
Sticky Properties
Saving Properties
Lazy Properties
Clickable Text
Fields
Not Intervals
Text Representations
Converting Representations
Selecting a Representation
Character Codes
Character Sets
Chars and Bytes
Splitting Characters
Scanning Charsets
Translation of Characters
Coding Systems
Input Methods
Locales
String Search
Regular Expressions
Regexp Search
Match Data
Saving Match Data
Standard Regexps
Searching and Case
Syntax of Regexps
Regexp Example
Syntax Descriptors
Syntax Table Functions
Parsing Expressions
Standard Syntax Tables
Syntax Table Internals
Syntax Class Table
Syntax Flags
Abbrev Mode
Abbrev Tables
Defining Abbrevs
Abbrev Files
Abbrev Expansion
Standard Abbrev Tables
Subprocess Creation
Synchronous Processes
Asynchronous Processes
Deleting Processes
Process Information
Input to Processes
Signals to Processes
Output from Processes
Sentinels
Network
Process Buffers
Filter Functions
Accepting Output
Starting Up
Getting Out
System Environment
Terminal Input
Terminal Output
Flow Control
Batch Mode
Startup Summary
Init File
Terminal-Specific
Command-Line Arguments
Killing Emacs
Suspending Emacs
Refresh Screen
Truncation
The Echo Area
Selective Display
Overlay Arrow
Temporary Displays
Waiting
Blinking
Usual Display
Beeping
Window Systems
Building Emacs
Pure Storage
Garbage Collection
Object Internals
Writing Emacs Primitives
Buffer Internals
Window Internals
Process Internals
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