# Agda: A dependently typed functional programming language and proof assistant

[ dependent-types, program ] [ Propose Tags ]

Agda is a dependently typed functional programming language: It has inductive families, which are similar to Haskell's GADTs, but they can be indexed by values and not just types. It also has parameterised modules, mixfix operators, Unicode characters, and an interactive Emacs interface (the type checker can assist in the development of your code).

Agda is also a proof assistant: It is an interactive system for writing and checking proofs. Agda is based on intuitionistic type theory, a foundational system for constructive mathematics developed by the Swedish logician Per Martin-Löf. It has many similarities with other proof assistants based on dependent types, such as Coq, Epigram and NuPRL.

This package includes both a command-line program (agda) and an Emacs mode. If you want to use the Emacs mode you can set it up by running agda-mode setup (see the README).

Note that the Agda library does not follow the package versioning policy, because it is not intended to be used by third-party packages.

## Flags

NameDescriptionDefaultType
cpphs

EnabledManual
epic

Install the Epic compiler.

DisabledManual

Use -f <flag> to enable a flag, or -f -<flag> to disable that flag. More info

Note: This package has metadata revisions in the cabal description newer than included in the tarball. To unpack the package including the revisions, use 'cabal get'.

#### Maintainer's Corner

For package maintainers and hackage trustees

[back to package description]

# Agda 2

Note that this README only discusses installation of Agda, not its standard library. See the Agda Wiki for information about the library.

## Prerequisites

You should also make sure that programs installed by cabal-install are on your shell's search path.

For instructions on installing a suitable version of Emacs under Windows, see [below]((#installing-emacs-under-windows).

Non-Windows users need to ensure that the development files for the C libraries zlib and ncurses are installed (see http://zlib.net and http://www.gnu.org/software/ncurses/). Your package manager may be able to install these files for you. For instance, on Debian or Ubuntu it should suffice to run

apt-get install zlib1g-dev libncurses5-dev


as root to get the correct files installed.

### Note on ghc's CPP language extension

Recent versions of Clang's preprocessor don't work well with Haskell. In order to get some dependencies to build, you may need to set up Cabal to have ghc use cpphs by default. You can do this by adding

program-default-options
ghc-options: -pgmPcpphs -optP--cpp


to your .cabal/config file. (You must be using cabal >= 1.18. Note that some packages may not compile with this option set.)

You don't need to set this option to install Agda from the current development source; Agda.cabal now uses cpphs.

## Installing Agda

There are several ways to install Agda:

### Using a binary package prepared for your platform

Recommended if such a package exists. See the Agda Wiki.

### Using a released source package from Hackage

Install the prerequisites mentioned below, then run the following commands:

cabal update
cabal install Agda
agda-mode setup


The last command tries to set up Emacs for use with Agda. As an alternative you can copy the following text to your .emacs file:

(load-file (let ((coding-system-for-read 'utf-8))
(shell-command-to-string "agda-mode locate")))


It is also possible (but not necessary) to compile the Emacs mode's files:

agda-mode compile


This can, in some cases, give a noticeable speedup.

WARNING: If you reinstall the Agda mode without recompiling the Emacs Lisp files, then Emacs may continue using the old, compiled files.

### Using the development version of the code

You can obtain tarballs of the development version from the Agda Wiki, or clone the repository.

Install the prerequisites discussed in Prerequisites.

Then, either:

(1a) Run the following commands in the top-level directory of the Agda source tree to install Agda:

cabal update
cabal install


(1b) Run agda-mode setup to set up Emacs for use with Agda. Alternatively, add the following text to your .emacs file:

(load-file (let ((coding-system-for-read 'utf-8))
(shell-command-to-string "agda-mode locate")))


It is also possible (but not necessary) to compile the Emacs mode's files:

agda-mode compile


This can, in some cases, give a noticeable speedup.

WARNING: If you reinstall the Agda mode without recompiling the Emacs Lisp files, then Emacs may continue using the old compiled files.

(2) Or, you can try to install Agda (including a compiled Emacs mode) by running the following command:

make install


## Configuring the Emacs mode

If you want to you can customise the Emacs mode. Just start Emacs and type the following:

M-x load-library RET agda2-mode RET
M-x customize-group RET agda2 RET


This is useful if you want to change the Agda search path, in which case you should change the agda2-include-dirs variable.

If you want some specific settings for the Emacs mode you can add them to agda2-mode-hook. For instance, if you do not want to use the Agda input method (for writing various symbols like ∀≥ℕ→π⟦⟧) you can add the following to your .emacs:

(add-hook 'agda2-mode-hook
'(lambda ()
; If you do not want to use any input method:
(deactivate-input-method)
; (In some versions of Emacs you should use
; deactivate-input-method.)

; If you want to use the X input method:
(set-input-method "X")))


Note that, on some systems, the Emacs mode changes the default font of the current frame in order to enable many Unicode symbols to be displayed. This only works if the right fonts are available, though. If you want to turn off this feature, then you should customise the agda2-fontset-name variable.

## Installing the Epic backend's dependencies

The Epic backend is experimental and requires that the Epic program is installed. You can install this program by giving the epic flag to cabal (but note that, at the time of writing, the Epic program does not build with certain recent versions of GHC):

### Installing from Hackage:

cabal update
cabal install Agda -fepic
agda-mode setup


### Installing from development sources using cabal

cabal update
cabal install -fepic
agda-mode setup


### Installing from development sources using make

make CABAL_OPTIONS=-fepic install


You can also install Epic directly:

cabal install epic


Note that Epic depends on other software: