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Cookbook/Compilers and interpreters

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= Prelude =
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== GHC ==
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A lot of functions are defined in the [[Prelude]]. The Prelude is a standard module imported by default into all Haskell module.
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{| class="wikitable"
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|-
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! Problem
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! Solution
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! Examples
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|-
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| compiling and linking an executable
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| --make
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|<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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|-
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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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|}
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Also, if you ever want to search for a function, based on the name, type or module, take a look at the excellent [[Hoogle]]. This is for a lot of people a must-have while debugging and writing Haskell programs.
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== GHCi ==
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= GHCi/Hugs =
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=== General ===
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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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{| class="wikitable"
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___ ___ _
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|-
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/ _ \ /\ /\/ __(_)
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! Problem
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/ /_\// /_/ / / | | GHC Interactive, version 6.6, for Haskell 98.
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! Solution
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/ /_\\/ __ / /___| | http://www.haskell.org/ghc/
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! Examples
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\____/\/ /_/\____/|_| Type :? for help.
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|-
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| checking a definition
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Loading package base ... linking ... done.
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| :i
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Prelude>
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|<haskell>
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Prelude> :i True
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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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data Bool = ... | True -- Defined in GHC.Bool
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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>
</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]
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`let' is also the way to create simple functions at the GHCi prompt
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Prelude> :t length
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<haskell>
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length :: [a] -> Int
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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>
</haskell>
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|-
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| loading a file
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| :l
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|<haskell>
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Prelude> :l Foo.hs
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[1 of 1] Compiling Foo ( Foo.hs, interpreted )
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Ok, modules loaded: Foo.
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</haskell>
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|-
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| reloading all loaded files
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| :r
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|<haskell>
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Prelude> :r
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</haskell>
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|}
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=== Debugging ===
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== Checking Types ==
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{| class="wikitable"
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To check the type of an expression or function, use the command `:t'
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|-
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<haskell>
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! Problem
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Prelude> :t x
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! Solution
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x :: Integer
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! Examples
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Prelude> :t "Hello"
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|-
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"Hello" :: [Char]
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| setting a break point
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</haskell>
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| :break
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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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<haskell>
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Prelude> :break 2 -- sets a break point in line 2
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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>
</haskell>
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|}
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== Hugs ==
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TODO

Current revision

Contents

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

2 GHCi

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

2.2 Debugging

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

3 Hugs

TODO

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