Basics

Overview

You can initialize an Etlas project using etlas init. The init command is interactive and you can find an example below.

Interactive Example

1. Create a new directory called eta-first and enter it.

   
   

   $ mkdir eta-first
   $ cd eta-first
   

   
   

2. Initialize the project with Etlas.

   
   

   Note: <[text-here]> means to type [text-here] and <Enter> means to press the Enter key.

   
   

   $ etlas init
   Package name? [default: eta-first] <Enter>
   Package version? [default: 0.1.0.0] <Enter>
   Please choose a license:
     1) GPL-2
     2) GPL-3
     3) LGPL-2.1
     4) LGPL-3
     5) AGPL-3
     6) BSD2
   * 7) BSD3
     8) MIT
     9) ISC
     10) MPL-2.0
     11) Apache-2.0
     12) PublicDomain
     13) AllRightsReserved
     14) Other (specify)
   Your choice? [default: BSD3] <Enter>
   Author name? [default: ...] <Enter>
   Maintainer email? [default: ...] <Enter>
   Project homepage URL? <Enter>
   Project synopsis? <Enter>
   Project category:
   * 1) (none)
     2) Codec
     3) Concurrency
     4) Control
     5) Data
     6) Database
     7) Development
     8) Distribution
     9) Game
     10) Graphics
     11) Language
     12) Math
     13) Network
     14) Sound
     15) System
     16) Testing
     17) Text
     18) Web
     19) Other (specify)
   Your choice? [default: (none)] <Enter>
   What does the package build:
     1) Library
     2) Executable
   Your choice? <2>
   What is the main module of the executable:
   * 1) Main.hs (does not yet exist, but will be created)
     2) Main.lhs (does not yet exist, but will be created)
     3) Other (specify)
   Your choice? [default: Main.hs (does not yet exist, but will be created)] <Enter>
   Source directory:
   * 1) (none)
     2) src
     3) Other (specify)
   Your choice? [default: (none)] <2>
   What base language is the package written in:
   * 1) Haskell2010
     2) Haskell98
     3) Other (specify)
   Your choice? [default: Haskell2010] <Enter>
   Add informative comments to each field in the cabal file (y/n)? [default: n] <Enter>
   
   Guessing dependencies...
   
   Generating LICENSE...
   Generating Setup.eta...
   Generating ChangeLog.md...
   Generating src/Main.hs...
   Generating eta-first.cabal...
   

   
   

   The project structure should look like this:

   
   

   eta-first
   - src
     - Main.hs
   - ChangeLog.md
   - LICENSE
   - Setup.hs
   - eta-first.cabal
   

   
   

3. Add the files Main.hs and Primes.hs in src/ as shown below.

   
   

   Main.hs

   1 2 3 4 5

   module Main where import Primes main = putStrLn $ "The 101st prime is " ++ show (primes !! 100)

   
   

   Primes.hs

   1 2 3 4 5

   module Primes where primes = filterPrime [2..] where filterPrime (p:xs) = p : filterPrime [x | x <- xs, x `mod` p /= 0]

   
   

4. Update eta-first.cabal, adding an other-modules: Primes field.

   
   

   eta-first.cabal

   name:                eta-first
   version:             0.1.0.0
   license:             BSD3
   license-file:        LICENSE
   author:              [your name]
   maintainer:          [your email]
   build-type:          Simple
   extra-source-files:  ChangeLog.md
   cabal-version:       >=1.10
   
   executable eta-first
     main-is:             Main.hs
     other-modules:       Primes
     build-depends:       base >=4.8 && <4.9
     hs-source-dirs:      src
     default-language:    Haskell2010
   

   
   

   Any additional modules you add to the project should be added at the same indentation level as the Primes entry, but below it.

   
   

5. Build and run your program.

   
   

   $ etlas run
   

   
   

Next Section

Now that we've initialized and built our first project, the next module will cover the fine details of building a project.