# Packages¶

Idris includes a simple build system for building packages and executables from a named package description file. These files can be used with the Idris compiler to manage the development process.

## Package Descriptions¶

A package description includes the following:

• A header, consisting of the keyword package followed by a package name. Package names can be any valid Idris identifier. The iPKG format also takes a quoted version that accepts any valid filename.
• Fields describing package contents, <field> = <value>.

At least one field must be the modules field, where the value is a comma separated list of modules. For example, given an idris package maths that has modules Maths.idr, Maths.NumOps.idr, Maths.BinOps.idr, and Maths.HexOps.idr, the corresponding package file would be:

package maths

modules = Maths
, Maths.NumOps
, Maths.BinOps
, Maths.HexOps


Other examples of package files can be found in the libs directory of the main Idris repository, and in third-party libraries.

## Using Package files¶

Idris itself is aware about packages, and special commands are available to help with, for example, building packages, installing packages, and cleaning packages. For instance, given the maths package from earlier we can use Idris as follows:

• idris --build maths.ipkg will build all modules in the package
• idris --install maths.ipkg will install the package, making it accessible by other Idris libraries and programs.
• idris --clean maths.ipkg will delete all intermediate code and executable files generated when building.

Once the maths package has been installed, the command line option --package maths makes it accessible (abbreviated to -p maths). For example:

idris -p maths Main.idr


## Testing Idris Packages¶

The integrated build system includes a simple testing framework. This framework collects functions listed in the ipkg file under tests. All test functions must return IO ().

When you enter idris --testpkg yourmodule.ipkg, the build system creates a temporary file in a fresh environment on your machine by listing the tests functions under a single main function. It compiles this temporary file to an executable and then executes it.

The tests themselves are responsible for reporting their success or failure. Test functions commonly use putStrLn to report test results. The test framework does not impose any standards for reporting and consequently does not aggregate test results.

For example, lets take the following list of functions that are defined in a module called NumOps for a sample package maths:

module Maths.NumOps

%access export -- to make functions under test visible

double : Num a => a -> a
double a = a + a

triple : Num a => a -> a
triple a = a + double a


A simple test module, with a qualified name of Test.NumOps can be declared as:

module Test.NumOps

import Maths.NumOps

%access export  -- to make the test functions visible

assertEq : Eq a => (given : a) -> (expected : a) -> IO ()
assertEq g e = if g == e
then putStrLn "Test Passed"
else putStrLn "Test Failed"

assertNotEq : Eq a => (given : a) -> (expected : a) -> IO ()
assertNotEq g e = if not (g == e)
then putStrLn "Test Passed"
else putStrLn "Test Failed"

testDouble : IO ()
testDouble = assertEq (double 2) 4

testTriple : IO ()
testTriple = assertNotEq (triple 2) 5


The functions assertEq and assertNotEq are used to run expected passing, and failing, equality tests. The actual tests are testDouble and testTriple, and are declared in the maths.ipkg file as follows:

package maths

modules = Maths.NumOps
, Test.NumOps

tests = Test.NumOps.testDouble
, Test.NumOps.testTriple


The testing framework can then be invoked using idris --testpkg maths.ipkg:

> idris --testpkg maths.ipkg
Type checking ./Maths/NumOps.idr
Type checking ./Test/NumOps.idr
Type checking /var/folders/63/np5g0d5j54x1s0z12rf41wxm0000gp/T/idristests144128232716531729.idr
Test Passed
Test Passed


Note how both tests have reported success by printing Test Passed as we arranged for with the assertEq and assertNoEq functions.

## Package Dependencies Using Atom¶

If you are using the Atom editor and have a dependency on another package, corresponding to for instance import Lightyear or import Pruviloj, you need to let Atom know that it should be loaded. The easiest way to accomplish that is with a .ipkg file. The general contents of an ipkg file will be described in the next section of the tutorial, but for now here is a simple recipe for this trivial case:

• Create a folder myProject.
• Add a file myProject.ipkg containing just a couple of lines:
package myProject

pkgs = pruviloj, lightyear

• In Atom, use the File menu to Open Folder myProject.