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How Mathematica does Unicode?
Xah Lee, 2010-12-05
This page explains some tech detail about how Mathematica uses unicode. This article may not be 100% accurate. I'm putting it up for now after spending a few hours. Am tsill working on it. If you are a Mathematica expert, please comment or correct.
Mathematica supports unicode, but does not use Unicode when saving to file. (See: UNICODE Basics: What's Character Encoding, UTF-8, and All That?)
Mathematica (mma) files uses ascii only. (See: Mathematica Notebook Technology.)
How does it support unicode if it uses only ASCII?
Mathematica's Named characters 「\[Name]」
It has a set of special characters with the syntax 「\[name]」. For example:
So, when you type 「\[Alpha]」 in mma, it is displayed as “α”. (All builtin symbols in mma starts with capital letter.)
Many of the named chars are also in unicode, but not all. Similarly, many Math Symbols in Unicode are not in this list. Also, unicode's chinese chars, arabic alphabets etc, are not in mma's named chars.
Map Between Unicode and Named Chars
When you paste a unicode char into mma, there is a map that automatically interprete the unicode as one of the named char.
So, for example, if you paste “α” (GREEK SMALL LETTER ALPHA; “U+x3b1”), it automatically becomes Mathematica's 「\[Alpha]」, and displayed as “α”.
Syntax for Unicode Char 「\:nnnn」
For any unicode that's not one of mma's named char (such as chinese chars), their syntax is this: 「\:nnnn」, where the nnnn is unicode's 4 digit hexidecimal representation of the char. For example, the chinese char “水” (water), unicode hex is “6c34”, in mma is: 「\:6c34」.
The above roughly summarize how mma takes unicode as input.
Some Named Chars has Builtin Meaning
Of the named chars, many has special meaning in mma. For example, 「\[Pi]」 is automatically considered identical to the builtin symbol 「Pi」, which in Mma means mathematical constant. (So, if you type 「N[\[Pi]]」 or 「N[\:03c0]」, they are displayed as 「N[π]」 with meaning of 「N[Pi]」, and if you evaluate it, you get “3.14159”.). Here's some examples of special meaning named chars.
|Glyph||Mma named char||Unicode name||Unicode hexidecimal||Default Interpretation|
|≥||\[GreaterEqual]||GREATER-THAN OR EQUAL TO||2265||GreaterThan 「>=」|
|π||\[Pi]||GREEK SMALL LETTER PI||03c0||Pi|
Note: it appears that it is possible to over-ride the default interpretation of named char to builtin symbol (function, constant), for all or some of the named char. (i haven't investigated on how yet.) See: MakeExpression.
Alias Shortcut for Named Chars
Some of the named char has one or more aliases for ease of input. For example, to enter α, you can type 【Esc a Esc】 or 【Esc alpha Esc】. Here's some examples:
- Characters that are alternatives to standard keyboard operators use these operators as their aliases (e.g. Esc -> Esc for , Esc && Esc for ∧).
- Most single-letter aliases stand for Greek letters.
- Capital-letter characters have aliases beginning with capital letters.
- When there is ambiguity in the assignment of aliases, a space is inserted at the beginning of the alias for the less common character (e.g. Esc -> Esc for \[Rule] and Esc -> Esc for \[RightArrow]).
- ! is inserted at the beginning of the alias for a Not character.
- TeX aliases begin with a backslash \.
- SGML aliases begin with an ampersand &.
- User-defined aliases conventionally begin with a dot or comma.
See: Special Characters.
List of Named Char with Special Meanings
... work in progress
Inputing Special Chars
You can input a special character by:
- Use one of the graphical palettes.
- Copy the unicode char somewhere and pasting it in mma.
- Type it like this: 「\[Name]」.
- Type the Unicode hexadecimal like this: 「\:nnnn」
- Type Esc, then the char's alias name, then Esc again.
... work in progress
See also: Wikipedia:LaTeX symbols