Where can I find a list of all GHC extensions

Question

I wanted to use {-# LANGUAGE OverloadedStrings #-} but I forgot how it's called. This kind of thing isn't hoogle-able, and also it takes some time finding using google*.

Is there somewhere a list of GHC extensions named as they are in the LANGUAGE pragma?

* My googling search journey:

Google
Haskell at wikipedia
GHC at wikipedia
GHC language features
Overload string literals
OverloadedStrings

score 29 · Answer 1 · answered Jun 08 '10 at 15:37

29

ghci's tab-completion knows. Type :set -X at a ghci prompt, then hit Tab, and you'll get a full list. Or :set -XFoo then Tab will get you a list of all extensions beginning with Foo.

answered Jun 08 '10 at 15:37

Ganesh Sittampalam

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Your answer is extra-useful because it also introduced me to `:set -X`! – yairchu Jun 08 '10 at 18:42

Travis Brown · Accepted Answer · 2010-06-08T15:31:29.833

25

The "Language options" section of the flag reference page has a list that's much more easily browseable than the language features page.

Once you're there a Ctrl-F search for "overloaded" takes you right to what you want.

edited Jun 08 '10 at 15:31

answered Jun 08 '10 at 15:03

Travis Brown

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Yep, and the ghc man page is also good. Always makes me feel sorry for people on manless platforms. – Thomas M. DuBuisson Jun 08 '10 at 15:47
The most recent docs for language extensions is https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/exts.html, and the most recent GHC flags docs is https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/flags.html – zbw Feb 14 '21 at 07:37

score 22 · Answer 3 · answered Jun 09 '10 at 09:40

22

$ ghc --supported-languages

(from GHC docs)

answered Jun 09 '10 at 09:40

yairchu

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`ghc --supported-languages | sort | sed -e "s/^$.*$$/{-# LANGUAGE \1 #-}/" | fzf | xclip` – Chris Stryczynski Nov 10 '18 at 15:13

score 3 · Answer 4 · edited Mar 09 '13 at 18:56

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ghc-mod for Emacs found here: http://hackage.haskell.org/package/ghc-mod, includes completion for language extensions. If you are an Emacs user, I suggest you to try it.

edited Mar 09 '13 at 18:56

amindfv

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answered Jun 08 '10 at 18:36

Tener

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Also with Spacemacs `SPC I s` starts ya-snippet with helm which is very handy to insert language extension. – mb14 Aug 27 '18 at 20:12

score 3 · Answer 5 · answered Jun 18 '10 at 00:37

3

When using Leksah IDE, selecting Package menu, then Edit Package menu item, then Extension tab also gives you a checkable list.

answered Jun 18 '10 at 00:37

DonnyD

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score 2 · Answer 6 · answered Mar 11 '13 at 18:39

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My dumb hacky way of doing such things:

$ man ghc | grep String
       -XExtendedDefaultRules   -XNoExtendedDefaultRules   -XOverloadedStrings
       -XNoOverloadedStrings  -XGADTs -XNoGADTs   -XGADTSyntax  -XNoGADTSyntax

answered Mar 11 '13 at 18:39

Dan Burton

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Damien Flament · Answer 7 · 2017-12-17T23:42:07.473

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The Cabal package provides a Language.Haskell.Extension module which exports a KnownExtension type whose each constructor is an extension.

The documentation of each constructor briefly describes the extension and provides a link to the GHC user guide.

edited Dec 17 '17 at 23:42

answered Dec 17 '17 at 23:35

Damien Flament

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Where can I find a list of all GHC extensions

7 Answers7