Unicode-symbols

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.

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.

base-unicode-symbols

Extra symbols for the base package.

 API docs: http://hackage.haskell.org/package/base-unicode-symbols

 darcs get http://code.haskell.org/~roelvandijk/code/base-unicode-symbols

Problematic symbols

Original	Symbol	Code point	Name
not	¬	U+AC	NOT SIGN

The problem with this symbol is that you would like to use it as a 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

====New symbol ideas==== (please add your own)

Original	Symbol	Code point	Name
Control.Monad.>>	≫	U+226B	MUCH GREATER-THAN

containers-unicode-symbols

Extra symbols for the containers package.

 API docs: http://hackage.haskell.org/package/containers-unicode-symbols

 darcs get http://code.haskell.org/~roelvandijk/code/containers-unicode-symbols

Fixities

What should the fixities for the following symbols be?

Symbol	Code point	Name
∪	U+222A	UNION
∩	U+2229	INTERSECTION
⊆	U+2286	SUBSET OF OR EQUAL TO
⊇	U+2287	SUPERSET OF OR EQUAL TO
⊈	U+2288	NEITHER A SUBSET OF NOR EQUAL TO
⊉	U+2289	NEITHER A SUPERSET OF NOR EQUAL TO
⊂	U+2282	SUBSET OF
⊃	U+2283	SUPERSET OF
⊄	U+2284	NOT A SUBSET OF
⊅	U+2285	NOT A SUPERSET OF

Intuitively there is a correspondence with numerical operators. Compare the following operators:

∪	+
⊃	>
⊄	≮

Likewise you would like similar associativities and precedence levels:

  x + y + z < w == ((x + y) + z) < w
  x ∪ y ∪ w ⊂ z == ((x ∪ y) ∪ z) ⊂ w

====New symbol ideas==== (please add your own)

Input methods

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

(please add info for other editors)

Emacs

Direct

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

Custom script

 darcs get http://code.haskell.org/~roelvandijk/code/emacs-unicode-symbols

In your .emacs file:

 (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 →.

Caveat: The author is an absolute Lisp newbie. Patches to above script are more than welcome.

Abbrev mode

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

Agda

Use Agda's input method.