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@ -5,6 +5,13 @@ $if(fontfamily)$
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$else$
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\usepackage{lmodern}
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$endif$
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\usepackage{xcolor}
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\usepackage{hyperref}
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\hypersetup{%
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colorlinks=false,% hyperlinks will be black
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linkbordercolor=red,% hyperlink borders will be red
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pdfborderstyle={/S/U/W 1}% border style will be underline of width 1pt
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}
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$if(linestretch)$
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\usepackage{setspace}
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\setstretch{$linestretch$}
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245
tutorial.md
245
tutorial.md
@ -4,20 +4,6 @@
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Stephen Diehl (<a class="author" href="https://twitter.com/smdiehl">@smdiehl</a> )
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|
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#### License
|
||||
|
||||
This code and text are dedicated to the public domain. You can copy, modify,
|
||||
distribute and perform the work, even for commercial purposes, all without
|
||||
asking permission.
|
||||
|
||||
You may copy and paste any code here verbatim into your codebase, wiki, blog,
|
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book or Haskell musical production as you see fit. The Markdown and Haskell
|
||||
source is [available on
|
||||
Github](https://github.com/sdiehl/wiwinwlh/tree/master/src). Pull requests are
|
||||
always accepted for changes and additional content. This is a living document.
|
||||
The only way this document will stay up to date is through community patches and
|
||||
[pull requests](https://github.com/sdiehl/wiwinwlh).
|
||||
|
||||
Version
|
||||
-------
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@ -28,6 +14,21 @@ This is the fifth major draft of this document since 2009.
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* **[EPUB Version](http://dev.stephendiehl.com/hask/tutorial.epub)**
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* **[Kindle Version](http://dev.stephendiehl.com/hask/tutorial.mobi)**
|
||||
|
||||
License
|
||||
--------
|
||||
|
||||
This code and text are dedicated to the public domain. You can copy, modify,
|
||||
distribute and perform the work, even for commercial purposes, all without
|
||||
asking permission.
|
||||
|
||||
You may copy and paste any code here verbatim into your codebase, wiki, blog,
|
||||
book or Haskell musical production as you see fit. The Markdown and Haskell
|
||||
source is [available on
|
||||
Github](https://github.com/sdiehl/wiwinwlh/tree/master/src). Pull requests are
|
||||
always accepted for changes and additional content. This is a living document.
|
||||
The only way this document will stay up to date is through the kindness of
|
||||
readers like you and community patches and [pull requests](https://github.com/sdiehl/wiwinwlh) on Github.
|
||||
|
||||
Basics
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||||
======
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@ -600,7 +601,7 @@ format to generate Cabal files. Hpack succeeds in DRYing (Don't Repeat Yourself)
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several sections of cabal files that are often quite repetative across large
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projects. Hpack uses a `package.yaml` file which the command line tool `hpack`
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generates whenever the project is built. Hpack can be integrated into Stack and
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||||
will generate cabal files whenever `stack build` is invoked.
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will generate cabal files whenever `stack build` is invoked.
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A small `package.yaml` file might look something like the following:
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@ -994,7 +995,7 @@ sensible:
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```haskell
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:seti -XNoImplicitPrelude
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:seti -XFlexibleContexts
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:seti -XFlexibleContexts
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:seti -XOverloadedStrings
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import Protolude
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```
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@ -1115,12 +1116,10 @@ build script for different service providers:
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* [Travis CI with Cabal](https://github.com/haskell-CI/haskell-ci/blob/master/.travis.yml)
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* [Travis CI with Stack](https://docs.haskellstack.org/en/stable/travis_ci/)
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|
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* [Circle CI with Cabal]
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* [Circle CI with Stack]
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* [Github Actions with Cabal]
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* [Github Actions with Stack]
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* [Circle CI with Cabal]()
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* [Circle CI with Stack]()
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* [Github Actions with Cabal]()
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* [Github Actions with Stack]()
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See also the official [haskell-ci]((https://github.com/haskell-CI/haskell-ci)
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repository.
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@ -1180,33 +1179,33 @@ import Data.List
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A import of select symbols into the local namespace:
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```haskell
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import Data.List (nub, sort)
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import Data.List (nub, sort)
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```
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A import into the global namespace masking a symbol:
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```haskell
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import Data.List hiding (nub)
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import Data.List hiding (nub)
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```
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A qualified import of `Data.Map` namespace into the local namespace.
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```haskell
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import qualified Data.Map
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import qualified Data.Map
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```
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A qualified import of `Data.Map` reassigned to `M` into the local namespace.
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```haskell
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import qualified Data.Map as M
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import qualified Data.Map as M
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```
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You may dump multiple modules into the same namespace so long as the symbols do
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not clash.
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```haskell
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import qualified Data.Map as M
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import qualified Data.Map.Strict as M
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import qualified Data.Map as M
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import qualified Data.Map.Strict as M
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```
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A main module is a special module which reserves the name `Main` and has a
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@ -1218,7 +1217,7 @@ module Main where
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main = print "Hello World!"
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```
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Functions
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Functions
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---------
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Functions are the central construction in Haskell. A function `f` of two
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@ -1259,7 +1258,7 @@ called *higher-order functions*. For example the following function applies a
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given argument `f` which is itelf a function to a value x twice.
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```haskell
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applyTwice f x = f (f x)
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applyTwice f x = f (f x)
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```
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@ -1290,8 +1289,8 @@ id = \x -> x
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```
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```haskell
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applyTwice :: (a -> a) -> a -> a
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applyTwice f x = f (f x)
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applyTwice :: (a -> a) -> a -> a
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applyTwice f x = f (f x)
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```
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@ -2210,7 +2209,7 @@ The following are all **false**:
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* Monads require knowing abstract mathematics.
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* Monads are unique to Haskell.
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See:
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See:
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* [What a Monad Is Not](http://wiki.haskell.org/What_a_Monad_is_not)
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@ -2339,7 +2338,7 @@ through the bind operation into the function ``g``.
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```
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See:
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See:
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* [Monad Laws](http://wiki.haskell.org/Monad_laws)
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@ -2432,7 +2431,7 @@ In the do-notation, the [monad laws](#laws) from above are equivalently written:
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g b
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```
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See:
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See:
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* [Haskell 2010: Do Expressions](http://www.haskell.org/onlinereport/haskell2010/haskellch3.html#x8-470003.14)
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@ -2671,7 +2670,7 @@ main :: IO ()
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main = putStrLn "What is your name: " >> (getLine >>= (\name -> putStrLn name))
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```
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See:
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See:
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||||
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* [Haskell 2010: Basic/Input Output](http://www.haskell.org/onlinereport/haskell2010/haskellch7.html)
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@ -2767,7 +2766,7 @@ abstractions that work for all current and future implementations. If you want a
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motivating reason for understanding monads, this is it! These insights are the
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essence of what I wish I knew about monads looking back.
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See:
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See:
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* [Control.Monad](http://hackage.haskell.org/package/base-4.9.0.0/docs/Control-Monad.html#g:4)
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@ -2943,7 +2942,7 @@ understanding of points (1), (2), and (3) and then trip on the simple fact that
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monads are the first example of a Haskell construct that is the confluence of
|
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all three.
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|
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See:
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See:
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||||
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||||
* [Monad Tutorial Fallacy](http://byorgey.wordpress.com/2009/01/12/abstraction-intuition-and-the-monad-tutorial-fallacy/)
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@ -3043,7 +3042,7 @@ Or equivalently:
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It's useful to remember that transformers compose *outside-in* but are *unrolled
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inside out*.
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|
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See:
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See:
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* [Monad Transformers: Step-By-Step](https://page.mi.fu-berlin.de/scravy/realworldhaskell/materialien/monad-transformers-step-by-step.pdf)
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@ -3246,7 +3245,7 @@ So we can generalize an existing transformer to lift an IO layer onto it.
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~~~~ {.haskell include="src/10-advanced-monads/mmorph.hs"}
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~~~~
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See:
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See:
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* [mmorph](https://hackage.haskell.org/package/mmorph)
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|
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@ -3338,14 +3337,14 @@ These extensions are typically used by advanced projects that push the limits of
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what is possible with Haskell to enforce complex invariants and very type-safe
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APIs.
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* PolyKinds
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* DataKinds
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* [PolyKinds](Promotion)
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* [DataKinds](Promotion)
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||||
* DerivingVia
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* GADTs
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* [GADTs]
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* RankNTypes
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* ExistentialQuantification
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* TypeFamilies
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* TypeInType
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* [TypeFamilies](Type Families)
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* [TypeInType]
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* TypeOperators
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* TypeApplications
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* UndecidableInstances
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@ -3866,8 +3865,8 @@ For example the simple custom List type:
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import GHC.Generics
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||||
data List a
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= Cons a (List a)
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data List a
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= Cons a (List a)
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||||
| Nil deriving
|
||||
(Generic)
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||||
```
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||||
@ -4166,7 +4165,7 @@ operator.
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||||
f $! x = let !vx = x in f vx
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||||
```
|
||||
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StrictData
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||||
StrictData
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||||
----------
|
||||
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||||
As of GHC 8.0 strictness annotations can be applied to all definitions in a
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@ -4672,7 +4671,8 @@ import Protolude
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||||
Protolude is one of the more conservative preludes and is developed by the
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||||
author of this document.
|
||||
|
||||
See:
|
||||
See:
|
||||
|
||||
* [Protolude Hackage](http://hackage.haskell.org/package/protolude)
|
||||
* [Protolude Github](https://www.github.com/protolude/protolude)
|
||||
|
||||
@ -6740,7 +6740,7 @@ Name
|
||||
----- --------------------------------- -----------------
|
||||
Catamorphism ``foldr :: (a -> b -> b) -> b -> [a] -> b`` Deconstructs a data structure
|
||||
Anamorphism ``unfoldr :: (b -> Maybe (a, b)) -> b -> [a]`` Constructs a structure level by level
|
||||
Hylomorphism ``hylo :: Functor f => (f b -> b) -> (a -> f a) -> a -> b``
|
||||
Hylomorphism ``hylo :: Functor f => (f b -> b) -> (a -> f a) -> a -> b`` Hylomorphism
|
||||
|
||||
```haskell
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||||
-- | A fix-point type.
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||||
@ -10617,18 +10617,18 @@ extension of the SQL standard. Consider the following tables specified in DDL.
|
||||
|
||||
```sql
|
||||
CREATE TABLE "books" (
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||||
"id" integer NOT NULL,
|
||||
"title" text NOT NULL,
|
||||
"author_id" integer,
|
||||
"subject_id" integer,
|
||||
Constraint "books_id_pkey" Primary Key ("id")
|
||||
"id" integer NOT NULL,
|
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"title" text NOT NULL,
|
||||
"author_id" integer,
|
||||
"subject_id" integer,
|
||||
Constraint "books_id_pkey" Primary Key ("id")
|
||||
);
|
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|
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CREATE TABLE "authors" (
|
||||
"id" integer NOT NULL,
|
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"last_name" text,
|
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"first_name" text,
|
||||
Constraint "authors_pkey" Primary Key ("id")
|
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"id" integer NOT NULL,
|
||||
"last_name" text,
|
||||
"first_name" text,
|
||||
Constraint "authors_pkey" Primary Key ("id")
|
||||
);
|
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```
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|
||||
@ -10862,7 +10862,7 @@ Flag Action
|
||||
``-ddump-asm`` The final assembly generated.
|
||||
``-ddump-llvm`` The final LLVM IR generated.
|
||||
|
||||
GHC Api
|
||||
GHC API
|
||||
-------
|
||||
|
||||
GHC can be used as a library to manipulate and transform Haskell source code
|
||||
@ -10930,6 +10930,101 @@ main = do
|
||||
putStrLn $ showSDoc ( ppr res )
|
||||
```
|
||||
|
||||
DynFlags
|
||||
--------
|
||||
|
||||
The internal compiler state of GHC is largely driven from a set of many
|
||||
configuration flags known as DynFlags. These flags are largely divided into four
|
||||
categories:
|
||||
|
||||
* Dump Flags
|
||||
* Warning Flags
|
||||
* Extension Flags
|
||||
* General Flags
|
||||
|
||||
These are flags are set via the following modifier functions:
|
||||
|
||||
```haskell
|
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dopt_set :: DynFlags -> DumpFlag -> DynFlags
|
||||
wopt_set :: DynFlags -> WarningFlag -> DynFlags
|
||||
xopt_set :: DynFlags -> Extension -> DynFlags
|
||||
gopt_set :: DynFlags -> GeneralFlag -> DynFlags
|
||||
```
|
||||
|
||||
See:
|
||||
|
||||
* [DynFlags](https://hackage.haskell.org/package/ghc-8.6.5/docs/DynFlags.html)
|
||||
|
||||
Package Databases
|
||||
-----------------
|
||||
|
||||
A package is a library of Haskell modules known to the compiler. Compilation of
|
||||
a Haskell module through Cabal uses a directory structure known as a package
|
||||
database. This directory is named `package.conf.d`, and contains a file for each
|
||||
package used for compiling a module and is combined with a binary cache of
|
||||
package's cabal data in `package.cache`.
|
||||
|
||||
When Cabal operates it stores the active package database in the environment
|
||||
variable: `GHC_PACKAGE_PATH`
|
||||
|
||||
To see which packages are currently available, use the ghc-pkg list command:
|
||||
|
||||
```bash
|
||||
$ ghc-pkg list
|
||||
/home/sdiehl/.ghcup/ghc/8.6.5/lib/ghc-8.6.5/package.conf.d
|
||||
Cabal-2.4.0.1
|
||||
array-0.5.3.0
|
||||
base-4.12.0.0
|
||||
binary-0.8.6.0
|
||||
bytestring-0.10.8.2
|
||||
containers-0.6.0.1
|
||||
deepseq-1.4.4.0
|
||||
directory-1.3.3.0
|
||||
filepath-1.4.2.1
|
||||
ghc-8.6.5
|
||||
ghc-boot-8.6.5
|
||||
ghc-boot-th-8.6.5
|
||||
ghc-compact-0.1.0.0
|
||||
ghc-heap-8.6.5
|
||||
ghc-prim-0.5.3
|
||||
ghci-8.6.5
|
||||
haskeline-0.7.4.3
|
||||
hpc-0.6.0.3
|
||||
integer-gmp-1.0.2.0
|
||||
libiserv-8.6.3
|
||||
mtl-2.2.2
|
||||
parsec-3.1.13.0
|
||||
pretty-1.1.3.6
|
||||
process-1.6.5.0
|
||||
rts-1.0
|
||||
stm-2.5.0.0
|
||||
template-haskell-2.14.0.0
|
||||
terminfo-0.4.1.2
|
||||
text-1.2.3.1
|
||||
time-1.8.0.2
|
||||
transformers-0.5.6.2
|
||||
unix-2.7.2.2
|
||||
xhtml-3000.2.2.1
|
||||
```
|
||||
|
||||
The package database can be queried for specific metadata of the cabal files
|
||||
associated with each package. For example to query the version of base library
|
||||
currently used for compilation we can query from the `ghc-pkg` command:
|
||||
|
||||
```bash
|
||||
$ ghc-pkg field base version
|
||||
version: 4.12.0.0
|
||||
|
||||
$ ghc-pkg field rts license
|
||||
license: BSD-3-Clause
|
||||
|
||||
$ ghc-pkg field haskeline exposed-modules
|
||||
exposed-modules:
|
||||
System.Console.Haskeline System.Console.Haskeline.Completion
|
||||
System.Console.Haskeline.History System.Console.Haskeline.IO
|
||||
System.Console.Haskeline.MonadException
|
||||
```
|
||||
|
||||
Abstract Syntax Tree
|
||||
--------------------
|
||||
|
||||
@ -10943,23 +11038,47 @@ TODO
|
||||
Outputable
|
||||
----------
|
||||
|
||||
GHC internally use a pretty printer class for rendering it's core structures out
|
||||
to text. This is based on the Wadler-Leijen style and uses a `Ouptutable` class
|
||||
as its interface:
|
||||
|
||||
```haskell
|
||||
class Outputable a where
|
||||
ppr :: a -> SDoc
|
||||
pprPrec :: Rational -> a -> SDoc
|
||||
```
|
||||
|
||||
The primary renderer for SDoc types is `showSDoc` which takes as argument a set
|
||||
of DynFlags which determine how the structure are printed.
|
||||
|
||||
```haskell
|
||||
showSDoc :: DynFlags -> SDoc -> String
|
||||
```
|
||||
|
||||
We can also cheat and use a unsafe show which uses a dummy set of DynFlags.
|
||||
|
||||
```haskell
|
||||
-- | Show a GHC.Outputable structure
|
||||
showGhc :: (GHC.Outputable a) => a -> String
|
||||
showGhc = GHC.showPpr GHC.unsafeGlobalDynFlags
|
||||
```
|
||||
|
||||
See:
|
||||
|
||||
* [Outputable](https://hackage.haskell.org/package/ghc-8.6.5/docs/Outputable.html)
|
||||
|
||||
Types
|
||||
-----
|
||||
|
||||
GHC has many datatypes but several of them are central data structures that are
|
||||
the core datatypes that are manipulated during compilation. These are divided
|
||||
into six core categories.
|
||||
|
||||
**Monads**
|
||||
|
||||
The GHC monads which encapsulate the compiler driver pipeline and statefully
|
||||
hold the interactions between the user and the internal compiler phases.
|
||||
|
||||
* GHC
|
||||
* P
|
||||
* Hsc
|
||||
@ -12673,7 +12792,7 @@ See:
|
||||
Pretty Printers
|
||||
---------------
|
||||
|
||||
There are many many many pretty printing libraries for Haskell.
|
||||
There are many many many pretty printing libraries for Haskell.
|
||||
|
||||
**Wadler-Leijen Style**
|
||||
|
||||
@ -12694,8 +12813,8 @@ There are many many many pretty printing libraries for Haskell.
|
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* prettyprinter-ansi-terminal
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* prettyprinter-compat-annotated-wl-pprint
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* prettyprinter-compat-ansi-wl-pprint
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* prettyprinter-compat-wl-pprint
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* prettyprinter-convert-ansi-wl-pprint
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||||
* prettyprinter-compat-wl-pprint
|
||||
* prettyprinter-convert-ansi-wl-pprint
|
||||
|
||||
**Specialised**
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||||
|
||||
|
||||
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