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Cookbook

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[[Category:How to]]
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== Haskell Cookbook ==
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* [[Cookbook/Compilers and interpreters|Haskell compilers and interpreters]]
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* [[Cookbook/Strings|Strings]]
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* [[Cookbook/Numbers|Numbers]]
* [[Cookbook/Numbers|Numbers]]
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* [[Cookbook/Lists and strings|Lists and strings]]
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* [[Cookbook/Other data structures|Other data structures]]
* [[Cookbook/Dates And Time|Dates and time]]
* [[Cookbook/Dates And Time|Dates and time]]
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* [[Cookbook/Lists|Lists]]
 
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* [[Cookbook/Other data structures|Other data structures]]
 
* [[Cookbook/Pattern matching|Pattern matching]]
* [[Cookbook/Pattern matching|Pattern matching]]
* [[Cookbook/Interactivity|Interactivity]]
* [[Cookbook/Interactivity|Interactivity]]
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* [[Cookbook/Databases access|Databases access]]
* [[Cookbook/Databases access|Databases access]]
* [[Cookbook/Graphical user interfaces|Graphical user interfaces]]
* [[Cookbook/Graphical user interfaces|Graphical user interfaces]]
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* [[Cookbook/PDF files|PDF files]]
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* [[Cookbook/FFI|FFI]]
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* [[Cookbook/Testing|Testing]]
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{{Template:Anonymousdraft}}
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== Similar projects for other programming languages ==
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* [http://cl-cookbook.sourceforge.net/ Common Lisp Cookbook]
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'''We need to start a Haskell centered cookbook (aka, not a [http://pleac.sourceforge.net/ PLEAC] clone)
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* [http://pleac.sourceforge.net/ PLEAC]
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* [http://www.zenspider.com/Languages/Ruby/Cookbook/index.html Ruby Cookbook]
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This page is based on the Scheme Cookbook at
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* [http://schemecookbook.org/Cookbook/WebHome Scheme Cookbook]
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http://schemecookbook.org/Cookbook/WebHome'''
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* [http://fssnip.net/ F# Snippets]
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== Prelude ==
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[[Category:FAQ]]
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[[Category:How to]]
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A lot of functions are defined in the "[http://www.haskell.org/hoogle/?q=Prelude Prelude]". Also, if you ever want to search for a function, based on the name, type or module, take a look at the excellent [http://www.haskell.org/hoogle/ Hoogle]. This is for a lot of people a must-have while debugging and writing Haskell programs.
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== GHCi/Hugs ==
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=== GHCi interaction ===
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To start GHCi from a command prompt, simply type `ghci'
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$ ghci
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___ ___ _
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/ _ \ /\ /\/ __(_)
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/ /_\// /_/ / / | | GHC Interactive, version 6.6, for Haskell 98.
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/ /_\\/ __ / /___| | http://www.haskell.org/ghc/
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\____/\/ /_/\____/|_| Type :? for help.
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Loading package base ... linking ... done.
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Prelude>
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[http://haskell.org/ghc/docs/latest/html/libraries/base/Prelude.html Prelude] is the "base" library of Haskell.
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To create variables at the GHCi prompt, use `let'
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<haskell>
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Prelude> let x = 5
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Prelude> x
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5
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Prelude> let y = 3
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Prelude> y
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3
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Prelude> x + y
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8
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</haskell>
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`let' is also the way to create simple functions at the GHCi prompt
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<haskell>
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Prelude> let fact n = product [1..n]
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Prelude> fact 5
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120
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</haskell>
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=== Checking Types ===
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To check the type of an expression or function, use the command `:t'
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<haskell>
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Prelude> :t x
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x :: Integer
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Prelude> :t "Hello"
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"Hello" :: [Char]
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</haskell>
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Haskell has the following types defined in the [http://haskell.org/ghc/docs/latest/html/libraries/base/Prelude.html Standard Prelude].
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<haskell>
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Int -- bounded, word-sized integers
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Integer -- unbounded integers
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Double -- floating point values
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Char -- characters
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String -- equivalent to [Char], strings are lists of characters
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() -- the unit type
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Bool -- booleans
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[a] -- lists
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(a,b) -- tuples / product types
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Either a b -- sum types
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Maybe a -- optional values
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</haskell>
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== PDF files ==
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For the following recipes you need to install [http://hackage.haskell.org/cgi-bin/hackage-scripts/package/HPDF HPDF].
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=== Creating an empty PDF file ===
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The following code creates an empty PDF file with the name "test1.pdf":
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<haskell>
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import Graphics.PDF
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main :: IO ()
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main = do
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let outputFileName= "test1.pdf"
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let defaultPageSize = PDFRect 0 0 200 300
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runPdf outputFileName standardDocInfo defaultPageSize $ do
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addPage Nothing
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</haskell>
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=== Pages with different sizes ===
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If you pass "Nothing" to the function [http://hackage.haskell.org/packages/archive/HPDF/latest/doc/html/Graphics-PDF-Document.html#v%3AaddPage addPage], the default page size will be used for the size of the new page.
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Let’s create three pages, the last two pages with different dimensions:
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<haskell>
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import Graphics.PDF
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main :: IO ()
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main = do
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let outputFileName= "test2.pdf"
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let defaultPageSize = PDFRect 0 0 200 300
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runPdf outputFileName standardDocInfo defaultPageSize $ do
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addPage Nothing
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addPage $ Just $ PDFRect 0 0 100 100
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addPage $ Just $ PDFRect 0 0 150 150
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</haskell>
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== FFI ==
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=== How to interface with C===
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Magnus has written [http://therning.org/magnus/archives/315 a nice example ] on how to call a C function operating on a user defined type.
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== Testing ==
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=== QuickCheck ===
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TODO
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=== HUnit ===
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TODO
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Current revision

1 Haskell Cookbook

2 Similar projects for other programming languages

Retrieved from "http://www.haskell.org/haskellwiki/Cookbook"

Categories: FAQ | How to