Unicode-symbols

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 Revision as of 13:39, 7 April 2010 (edit) (Removed hlint problems section (fixed in hlint-1.6.21))← Previous diff Revision as of 17:41, 23 January 2013 (edit) (undo)m (→Vim)Next diff → (28 intermediate revisions not shown.) Line 14: Line 14: GHC offers the [http://www.haskell.org/ghc/docs/latest/html/users_guide/syntax-extns.html#unicode-syntax UnicodeSyntax] language extension. If you decide to use Unicode in your Haskell source then this extension can greatly improve how it looks. GHC offers the [http://www.haskell.org/ghc/docs/latest/html/users_guide/syntax-extns.html#unicode-syntax UnicodeSyntax] language extension. If you decide to use Unicode in your Haskell source then this extension can greatly improve how it looks. + + Simply put the following above a module to enable unicode syntax: + {-# LANGUAGE UnicodeSyntax #-} == base-unicode-symbols == == base-unicode-symbols == Line 20: Line 23: API docs: http://hackage.haskell.org/package/base-unicode-symbols API docs: http://hackage.haskell.org/package/base-unicode-symbols + github: https://github.com/roelvandijk/base-unicode-symbols + checkout: git clone git://github.com/roelvandijk/base-unicode-symbols.git - darcs get http://code.haskell.org/~roelvandijk/code/base-unicode-symbols + ==== Problematic symbols ==== - + - ====Problematic symbols==== + {| class="wikitable" border="1" {| class="wikitable" border="1" |- |- Line 35: Line 38: | U+AC | U+AC | NOT SIGN | NOT SIGN + |- + | lambda + | λ + | U+03BB + | GREEK SMALL LETTER LAMDA |} |} - The problem with this symbol is that you would like to use it as a unary prefix operator: + The problem with the NOT symbol is that you would like to use it as an unary prefix operator: ¬(¬x) ≡ x ¬(¬x) ≡ x Unfortunately this is not valid Haskell. The following is: Unfortunately this is not valid Haskell. The following is: Line 43: Line 51: not (not x) ≡ x not (not x) ≡ x - ====New symbol ideas==== (''please add your own'') + The problem with the LAMBDA symbol is that it is classified as an alphabetic character, so it can be used as part of a name. See the [http://hackage.haskell.org/trac/ghc/ticket/1102 discussion for GHC]. + + ==== New symbol ideas ==== + (''please add your own'') + + I'm thinking of adding the following symbol as another alternative for (*). + + {| class="wikitable" border="1" + |- + ! Original + ! Symbol + ! Code point + ! Name + |- + | (*) + | × + | U+D7 + | MULTIPLICATION SIGN + |} + + 2 * 3 ≡ 6 + 2 ⋅ 3 ≡ 6 + 2 × 3 ≡ 6 + + A disadvantage of this symbol is its similarity to the letter x: + sqr x = x × x + + {| class="wikitable" border="1" + |- + ! Original + ! Symbol + ! Code point + ! Name + |- + | Bool + | 𝔹 + | U+1D539 + | MATHEMATICAL DOUBLE-STRUCK CAPITAL B + |} + + This idea is an extension of + + type ℕ = Integer + + and + + type ℚ = Ratio ℕ + + The advantage is that it looks nice and that it is a logical extension of ℕ, ℚ and ℝ. The disadvantage is that their is no documented prior use of this character to denote boolean values. This could be detrimental to the readability of code. + + Example: + + (∧) ∷ 𝔹 → 𝔹 → 𝔹 == containers-unicode-symbols == == containers-unicode-symbols == Line 50: Line 110: API docs: http://hackage.haskell.org/package/containers-unicode-symbols API docs: http://hackage.haskell.org/package/containers-unicode-symbols + github: https://github.com/roelvandijk/containers-unicode-symbols + checkout: git clone git://github.com/roelvandijk/containers-unicode-symbols.git - darcs get http://code.haskell.org/~roelvandijk/code/containers-unicode-symbols + ==== New symbol ideas ==== - + (''please add your own'') - ====New symbol ideas==== (''please add your own'') + == Input methods == == Input methods == These symbols are all very nice but how do you type them? These symbols are all very nice but how do you type them? + + Wikipedia has a helpful article: http://en.wikipedia.org/wiki/Unicode_input (''please add info for other editors'') (''please add info for other editors'') Line 65: Line 128: '''Direct''' '''Direct''' - Enter symbols directly: [http://www.gnu.org/software/emacs/manual/html_node/emacs/International-Chars.html C-x 8 RET], then type either the character's name or its hexadecimal code point. + Enter symbols directly: [http://www.gnu.org/software/emacs/manual/html_node/emacs/International-Chars.html C-x 8 RET] (ucs-insert), then type either the character's name or its hexadecimal code point. - '''Custom script''' + '''TeX input method''' - darcs get http://code.haskell.org/~roelvandijk/code/emacs-unicode-symbols + The TeX input method, invoked with M-x set-input-method and entering TeX allows you to enter Unicode characters by typing in TeX-like sequences. For example, typing \lambda inserts a λ. - In your .emacs file: + This is probably the most convenient input method for casual use. - (load "~/elisp/emacs-unicode-symbols/haskell-symbols") + - (defun haskell-unicode () (local-set-key (kbd "C-M-u") 'replace-haskell-unicode)) + - (add-hook 'haskell-mode-hook 'haskell-unicode) + - With above hook installed navigate the point to right after a normal symbol like '''->''' and press '''C-M-u''' to transform it into a beautiful '''→'''. + A list of available sequences may be viewed with M-x describe-input-method - ''Caveat'': The author is an absolute Lisp newbie. Patches to above script are more than welcome. + '''Custom input method''' + + I wrote my own input method: + + github: https://github.com/roelvandijk/emacs-haskell-unicode-input-method + checkout: git clone git://github.com/roelvandijk/emacs-haskell-unicode-input-method.git + + To automically load in haskell-mode put the following code in your .emacs file: + (require 'haskell-unicode-input-method) + (add-hook 'haskell-mode-hook + (lambda () (set-input-method "haskell-unicode"))) + + Make sure the directory containing the .elisp file is in your load-path, for example: + (add-to-list 'load-path "~/.elisp/emacs-haskell-unicode-input-method") + + To manually enable use M-x set-input-method or C-x RET C-\ with haskell-unicode. Note that the elisp file must be evaluated for this to work. + + Now you can simply type -> and it is immediately replaced with →. Use C-\ to toggle the input method. To see a table of all key sequences use M-x describe-input-method haskell-unicode. A sequence like <= is ambiguous and can mean either or . Typing it presents you with a choice. Type 1 or 2 to select an option or keep typing to use the default option. + + If you don't like the highlighting of partially matching tokens you can turn it off: + + (setq input-method-highlight-flag nil) '''Abbrev mode''' '''Abbrev mode''' Line 87: Line 168: Use Agda's [http://wiki.portal.chalmers.se/agda/pmwiki.php?n=Docs.UnicodeInput input method]. Use Agda's [http://wiki.portal.chalmers.se/agda/pmwiki.php?n=Docs.UnicodeInput input method]. + + === Vim === + + (''real Vim users might want to expand this section'') + + '''Direct''' + + * Decimal value: type '''C-Vnnn''' where 0 ≤ nnn ≤ 255. + * Octal value: type '''C-VOnnn''' or '''C-Vonnn''' where 0 ≤ nnn ≤ 377. + * Hex value: type '''C-VXnn''' or '''C-Vxnn''' where 0 ≤ nn ≤ FF. + * Hex value for BMP codepoints: type '''C-Vunnnn''' where 0 ≤ nnnn ≤ FFFF. + * Hex value for any codepoint: type '''C-VUnnnnnnnn''' where 0 ≤ nnnnnnnn ≤ FFFFFFFF. + + '''Automatic Unicode Transformation''' + + Furthermore, there is a Haskell file type plugin called [https://github.com/frerich/unicode-haskell unicode-haskell] which automatically transforms ASCII character sequences (e.g. -> and many others) to Unicode when loading Haskell source code - and the data is converted back when saving. That way, the source code remains plain ASCII on disk but uses nice Unicode characters in vim/gvim. Furthermore, the plugin will automatically replace ASCII sequences with their Unicode equivalents as you type. + + The Vim conceal definitions in haskellmode-vim pleasantly mask most of usual symbols with the unicode equivalent but have no effect on the actual source code (in my experience, this is much faster than unicode-haskell and it's much easier to edit). While in normal mode, the concealed characters on the current line will be displayed as ASCII. In insert mode and on lines other than the current one in normal mode, Unicode characters will be displayed. + + === SciTE === + + See [[Tips_for_using_SciTE_with_Haskell]] + + === Sublime Text 2 === + + Syntax highlighting for the GHC unicode syntax is not supported in the default configuration as of version 2.0.1. However the following patch, when applied to Packages/Haskell/Haskell.tmLanguage, does enable this: https://gist.github.com/3744568 + + Insert the following snippet into user key bindings to conveniently type unicode operators in Haskell code: https://gist.github.com/3766192 . For example, typing "->" will automatically insert "→". + + === System wide === + + '''m17n input methods''' + + A set of input methods has been written by Urs Holzer for the [http://www.m17n.org m17n] library. The main goal of Urs is to build input methods for mathematical characters. However, most of the symbols used in the *-unicode-symbols packages can be written using Urs's methods. More information is available at [http://www.andonyar.com/rec/2008-03/mathinput/ Input Methods for Mathematics] page. For most Linux distributions, just download a [http://www.andonyar.com/rec/2008-03/mathinput/methods.tar.gz tarball], extract *.mim files to /usr/share/m17n and enable iBus for input methods. + + == Fonts == + + The following free fonts have good Unicode coverage: + + * [http://www.gnome.org/fonts/ Bitstream Vera Font Family] + * [http://dejavu-fonts.org/wiki/Main_Page DejaVu Font Family] + * [http://linuxlibertine.sourceforge.net/ Linux Libertine Font] + * [https://www.redhat.com/promo/fonts/ RedHat Liberation Fonts]

1 Overview

An overview of the packages that provide Unicode symbols.

Naming: A package X-unicode-symbols defines new symbols for functions and operators from the package X.

All symbols are documented with their actual definition and information regarding their Unicode code point. They should be completely interchangeable with their definitions.

Alternatives for existing operators have the same fixity. New operators will have a suitable fixity defined.

1.1 UnicodeSyntax

GHC offers the UnicodeSyntax language extension. If you decide to use Unicode in your Haskell source then this extension can greatly improve how it looks.

Simply put the following above a module to enable unicode syntax:

 {-# LANGUAGE UnicodeSyntax #-}


2 base-unicode-symbols

Extra symbols for the base package.

 API docs: http://hackage.haskell.org/package/base-unicode-symbols
github: https://github.com/roelvandijk/base-unicode-symbols
checkout: git clone git://github.com/roelvandijk/base-unicode-symbols.git


2.1 Problematic symbols

Original Symbol Code point Name
not ¬ U+AC NOT SIGN
lambda λ U+03BB GREEK SMALL LETTER LAMDA

The problem with the NOT symbol is that you would like to use it as an unary prefix operator:

 ¬(¬x) ≡ x


Unfortunately this is not valid Haskell. The following is:

 (¬)((¬)x) ≡ x


But you can hardly call that an improvement over the simple:

 not (not x) ≡ x


The problem with the LAMBDA symbol is that it is classified as an alphabetic character, so it can be used as part of a name. See the discussion for GHC.

2.2 New symbol ideas

(please add your own)

I'm thinking of adding the following symbol as another alternative for (*).

Original Symbol Code point Name
(*) × U+D7 MULTIPLICATION SIGN
 2 * 3 ≡ 6
2 ⋅ 3 ≡ 6
2 × 3 ≡ 6


A disadvantage of this symbol is its similarity to the letter x:

 sqr x = x × x

Original Symbol Code point Name
Bool 𝔹 U+1D539 MATHEMATICAL DOUBLE-STRUCK CAPITAL B

This idea is an extension of

 type ℕ = Integer


and

 type ℚ = Ratio ℕ


The advantage is that it looks nice and that it is a logical extension of ℕ, ℚ and ℝ. The disadvantage is that their is no documented prior use of this character to denote boolean values. This could be detrimental to the readability of code.

Example:

 (∧) ∷ 𝔹 → 𝔹 → 𝔹


3 containers-unicode-symbols

Extra symbols for the containers package.

 API docs: http://hackage.haskell.org/package/containers-unicode-symbols
github: https://github.com/roelvandijk/containers-unicode-symbols
checkout: git clone git://github.com/roelvandijk/containers-unicode-symbols.git


3.1 New symbol ideas

(please add your own)

4 Input methods

These symbols are all very nice but how do you type them?

Wikipedia has a helpful article: http://en.wikipedia.org/wiki/Unicode_input

(please add info for other editors)

4.1 Emacs

Direct

Enter symbols directly: C-x 8 RET (ucs-insert), then type either the character's name or its hexadecimal code point.

TeX input method

The TeX input method, invoked with M-x set-input-method and entering TeX allows you to enter Unicode characters by typing in TeX-like sequences. For example, typing \lambda inserts a λ.

This is probably the most convenient input method for casual use.

A list of available sequences may be viewed with M-x describe-input-method

Custom input method

I wrote my own input method:

 github: https://github.com/roelvandijk/emacs-haskell-unicode-input-method
checkout: git clone git://github.com/roelvandijk/emacs-haskell-unicode-input-method.git



To automically load in haskell-mode put the following code in your .emacs file:

 (require 'haskell-unicode-input-method)
(add-hook 'haskell-mode-hook
(lambda () (set-input-method "haskell-unicode")))


Make sure the directory containing the .elisp file is in your load-path, for example:

 (add-to-list 'load-path "~/.elisp/emacs-haskell-unicode-input-method")


To manually enable use M-x set-input-method or C-x RET C-\ with haskell-unicode. Note that the elisp file must be evaluated for this to work.

Now you can simply type -> and it is immediately replaced with →. Use C-\ to toggle the input method. To see a table of all key sequences use M-x describe-input-method haskell-unicode. A sequence like <= is ambiguous and can mean either or . Typing it presents you with a choice. Type 1 or 2 to select an option or keep typing to use the default option.

If you don't like the highlighting of partially matching tokens you can turn it off:

 (setq input-method-highlight-flag nil)


Abbrev mode

The Abbrev mode is not suitable since it only deals with words, not operators.

Agda

Use Agda's input method.

4.2 Vim

(real Vim users might want to expand this section)

Direct

• Decimal value: type C-Vnnn where 0 ≤ nnn ≤ 255.
• Octal value: type C-VOnnn or C-Vonnn where 0 ≤ nnn ≤ 377.
• Hex value: type C-VXnn or C-Vxnn where 0 ≤ nn ≤ FF.
• Hex value for BMP codepoints: type C-Vunnnn where 0 ≤ nnnn ≤ FFFF.
• Hex value for any codepoint: type C-VUnnnnnnnn where 0 ≤ nnnnnnnn ≤ FFFFFFFF.

Automatic Unicode Transformation

Furthermore, there is a Haskell file type plugin called unicode-haskell which automatically transforms ASCII character sequences (e.g. -> and many others) to Unicode when loading Haskell source code - and the data is converted back when saving. That way, the source code remains plain ASCII on disk but uses nice Unicode characters in vim/gvim. Furthermore, the plugin will automatically replace ASCII sequences with their Unicode equivalents as you type.

The Vim conceal definitions in haskellmode-vim pleasantly mask most of usual symbols with the unicode equivalent but have no effect on the actual source code (in my experience, this is much faster than unicode-haskell and it's much easier to edit). While in normal mode, the concealed characters on the current line will be displayed as ASCII. In insert mode and on lines other than the current one in normal mode, Unicode characters will be displayed.

4.4 Sublime Text 2

Syntax highlighting for the GHC unicode syntax is not supported in the default configuration as of version 2.0.1. However the following patch, when applied to Packages/Haskell/Haskell.tmLanguage, does enable this: https://gist.github.com/3744568

Insert the following snippet into user key bindings to conveniently type unicode operators in Haskell code: https://gist.github.com/3766192 . For example, typing "->" will automatically insert "→".

4.5 System wide

m17n input methods

A set of input methods has been written by Urs Holzer for the m17n library. The main goal of Urs is to build input methods for mathematical characters. However, most of the symbols used in the *-unicode-symbols packages can be written using Urs's methods. More information is available at Input Methods for Mathematics page. For most Linux distributions, just download a tarball, extract *.mim files to /usr/share/m17n and enable iBus for input methods.

5 Fonts

The following free fonts have good Unicode coverage: