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= Prelude =
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== GHC ==
  
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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{| class="wikitable"
 +
|-
 +
!  Problem
 +
!  Solution
 +
!  Examples
 +
|-
 +
|  compiling and linking an executable
 +
|  --make
 +
|<pre>ghc --make Main.hs              --> Main</pre>
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|-
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|  compiling without linking
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|  -c
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|<pre>ghc -c Foo.hs                    --> Foo.hi, Foo.o</pre>
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|-
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|  generating Assembler code
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|  -S
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|<pre>ghc -S Foo.hs                    --> Foo.hi, Foo.s</pre>
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|-
 +
|  generating C code
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|  -C
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|<pre>ghc -C Foo.hs                    --> Foo.hc, Foo.hi</pre>
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|-
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|  linking files into an executable
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|  -o
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|<pre>ghc -o test Foo.o Bar.o Baz.p    --> test</pre>
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|}
  
= GHCi/Hugs =
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== GHCi ==
== 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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=== General ===
      ___        ___ _
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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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{| class="wikitable"
 
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|-
To create variables at the GHCi prompt, use `let'
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!  Problem
<haskell>
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!  Solution
Prelude> let x = 5
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!  Examples
Prelude> x
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|-
5
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|  checking a definition
Prelude> let y = 3
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|  :i
Prelude> y
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|<haskell>
3
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Prelude> :i True
Prelude> x + y
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data Bool = ... | True  -- Defined in GHC.Bool
8
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</haskell>
 
</haskell>
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|-
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|  checking a type
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|  :t
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|<haskell>
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Prelude> :t "Hello"
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"Hello" :: [Char]
  
`let' is also the way to create simple functions at the GHCi prompt
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Prelude> :t length
<haskell>
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length :: [a] -> Int
Prelude> let fact n = product [1..n]
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Prelude> fact 5
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120
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</haskell>
 
</haskell>
 +
|-
 +
|  loading a file
 +
|  :l
 +
|<haskell>
 +
Prelude> :l Foo.hs
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[1 of 1] Compiling Foo              ( Foo.hs, interpreted )
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Ok, modules loaded: Foo.
 +
</haskell>
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|-
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|  reloading all loaded files
 +
|  :r
 +
|<haskell>
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Prelude> :r
 +
</haskell>
 +
|}
  
 +
=== Debugging ===
  
== Checking Types ==
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{| class="wikitable"
To check the type of an expression or function, use the command `:t'
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|-
<haskell>
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!  Problem
Prelude> :t x
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!  Solution
x :: Integer
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!  Examples
Prelude> :t "Hello"
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|-
"Hello" :: [Char]
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|  setting a break point
</haskell>
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:break
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>
<haskell>
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Prelude> :break 2    -- sets a break point in line 2
    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>
 
</haskell>
 +
|}
 +
 +
== Hugs ==
 +
 +
TODO

Latest revision as of 08:33, 25 January 2010

Contents

[edit] 1 GHC

Problem Solution Examples
compiling and linking an executable --make
ghc --make Main.hs               --> Main
compiling without linking -c
ghc -c Foo.hs                    --> Foo.hi, Foo.o
generating Assembler code -S
ghc -S Foo.hs                    --> Foo.hi, Foo.s
generating C code -C
ghc -C Foo.hs                    --> Foo.hc, Foo.hi
linking files into an executable -o
ghc -o test Foo.o Bar.o Baz.p    --> test

[edit] 2 GHCi

[edit] 2.1 General

Problem Solution Examples
checking a definition  :i
Prelude> :i True
data Bool = ... | True  -- Defined in GHC.Bool
checking a type  :t
Prelude> :t "Hello"
"Hello" :: [Char]
 
Prelude> :t length
length :: [a] -> Int
loading a file  :l
Prelude> :l Foo.hs
[1 of 1] Compiling Foo              ( Foo.hs, interpreted )
Ok, modules loaded: Foo.
reloading all loaded files  :r
Prelude> :r

[edit] 2.2 Debugging

Problem Solution Examples
setting a break point  :break
Prelude> :break 2    -- sets a break point in line 2

[edit] 3 Hugs

TODO