Getting Started¶
Prerequisites¶
Before installing Idris, you will need to make sure you have all of the necessary libraries and tools. You will need:
- A fairly recent version of GHC. The earliest version we currently test with is 7.6.3.
- The GNU Multiple Precision Arithmetic Library (GMP) is available from MacPorts/Homebrew and all major Linux distributions.
Downloading and Installing¶
The easiest way to install Idris, if you have all of the prerequisites, is to type:
cabal update; cabal install idris
This will install the latest version released on Hackage, along with any dependencies. If, however, you would like the most up to date development version you can find it, as well as build instructions, on GitHub at: https://github.com/idris-lang/Idris-dev.
If you haven’t previously installed anything using Cabal, then Idris
may not be on your path. Should the Idris executable not be found
please ensure that you have added ~/.cabal/bin
to your $PATH
environment variable. Mac OS X users may find they need to add
~/Library/Haskell/bin
instead, and Windows users will typically
find that Cabal installs programs in %HOME%\AppData\Roaming\cabal\bin
.
To check that installation has succeeded, and to write your first
Idris program, create a file called hello.idr
containing the
following text:
module Main
main : IO ()
main = putStrLn "Hello world"
If you are familiar with Haskell, it should be fairly clear what the
program is doing and how it works, but if not, we will explain the
details later. You can compile the program to an executable by
entering idris hello.idr -o hello
at the shell prompt. This will
create an executable called hello
, which you can run:
$ idris hello.idr -o hello
$ ./hello
Hello world
Please note that the dollar sign $
indicates the shell prompt!
Some useful options to the Idris command are:
-o prog
to compile to an executable calledprog
.--check
type check the file and its dependencies without starting the interactive environment.--package pkg
add package as dependency, e.g.--package contrib
to make use of the contrib package.--help
display usage summary and command line options.
The Interactive Environment¶
Entering idris
at the shell prompt starts up the interactive
environment. You should see something like the following:
$ idris
____ __ _
/ _/___/ /____(_)____
/ // __ / ___/ / ___/ Version 1.0
_/ // /_/ / / / (__ ) http://www.idris-lang.org/
/___/\__,_/_/ /_/____/ Type :? for help
Idris>
This gives a ghci
style interface which allows evaluation of, as
well as type checking of, expressions; theorem proving, compilation;
editing; and various other operations. The command :?
gives a list
of supported commands. Below, we see an example run in
which hello.idr
is loaded, the type of main
is checked and
then the program is compiled to the executable hello
. Type
checking a file, if successful, creates a bytecode version of the file
(in this case hello.ibc
) to speed up loading in future. The
bytecode is regenerated if the source file changes.
$ idris hello.idr
____ __ _
/ _/___/ /____(_)____
/ // __ / ___/ / ___/ Version 1.0
_/ // /_/ / / / (__ ) http://www.idris-lang.org/
/___/\__,_/_/ /_/____/ Type :? for help
Type checking ./hello.idr
*hello> :t main
Main.main : IO ()
*hello> :c hello
*hello> :q
Bye bye
$ ./hello
Hello world