Difference between revisions of "Cookbook"
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| + | == Haskell Cookbook == |
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| − | '''We need to start a GOOD (aka, not a PLEAC clone) Haskell cookbook. |
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| + | * [[Cookbook/Compilers and interpreters|Haskell compilers and interpreters]] |
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| − | This page is based on the Scheme Cookbook at |
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| + | * [[Cookbook/Numbers|Numbers]] |
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| − | http://schemecookbook.org/Cookbook/WebHome''' |
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| + | * [[Cookbook/Lists and strings|Lists and strings]] |
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| − | == GHCi/Hugs == |
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| + | * [[Cookbook/Other data structures|Other data structures]] |
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| − | === GHCi Interaction === |
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| + | * [[Cookbook/Dates And Time|Dates and time]] |
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| − | To start GHCi from a command prompt, simply type `ghci' |
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| + | * [[Cookbook/Pattern matching|Pattern matching]] |
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| + | * [[Cookbook/Interactivity|Interactivity]] |
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| + | * [[Cookbook/Files|Files]] |
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| + | * [[Cookbook/Network programming|Network programming]] |
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| + | * [[Cookbook/XML|XML]] |
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| + | * [[Cookbook/Databases access|Databases access]] |
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| + | * [[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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| + | == Similar projects for other programming languages == |
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| − | $ ghci |
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| + | * [http://cl-cookbook.sourceforge.net/ Common Lisp Cookbook] |
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| − | ___ ___ _ |
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| + | * [http://pleac.sourceforge.net/ PLEAC] |
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| − | / _ \ /\ /\/ __(_) |
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| + | * [http://www.zenspider.com/Languages/Ruby/Cookbook/index.html Ruby Cookbook] |
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| − | / /_\// /_/ / / | | GHC Interactive, version 6.6, for Haskell 98. |
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| + | * [http://schemecookbook.org/Cookbook/WebHome Scheme Cookbook] |
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| − | / /_\\/ __ / /___| | http://www.haskell.org/ghc/ |
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| + | * [http://fssnip.net/ F# Snippets] |
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| − | \____/\/ /_/\____/|_| Type :? for help. |
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| + | [[Category:FAQ]] |
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| − | |||
| + | [[Category:How to]] |
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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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| − | |||
| − | == 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 y |
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| − | y :: Integer |
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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 -- strings |
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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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| − | |||
| − | == Strings == |
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| − | === Input === |
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| − | Strings can be read as input using [http://haskell.org/ghc/docs/latest/html/libraries/base/Prelude.html#v%3AgetLine getLine]. |
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| − | <haskell> |
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| − | Prelude> getLine |
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| − | Foo bar baz |
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| − | "Foo bar baz" |
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| − | </haskell> |
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| − | |||
| − | === Output === |
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| − | Strings can be output in a number of different ways. |
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| − | <haskell> |
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| − | Prelude> putStr "Foo" |
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| − | FooPrelude> |
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| − | </haskell> |
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| − | As you can see, [http://haskell.org/ghc/docs/latest/html/libraries/base/Prelude.html#v%3AputStr putStr] does not include the newline character `\n'. We can either use putStr like this: |
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| − | <haskell> |
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| − | Prelude> putStr "Foo\n" |
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| − | Foo |
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| − | </haskell> |
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| − | Or use [http://haskell.org/ghc/docs/latest/html/libraries/base/Prelude.html#v%3AputStrLn putStrLn], which is already in the Standard Prelude |
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| − | <haskell> |
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| − | Prelude> putStrLn "Foo" |
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| − | Foo |
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| − | </haskell> |
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| − | We can also use [http://haskell.org/ghc/docs/latest/html/libraries/base/Prelude.html#v%3Aprint print] to print a string, '''including the quotation marks.''' |
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| − | <haskell> |
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| − | Prelude> print "Foo" |
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| − | "Foo" |
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| − | </haskell> |
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| − | |||
| − | === Concatenation === |
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| − | Concatenation of strings is done with the `++' operator. |
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| − | <haskell> |
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| − | Prelude> "foo" ++ "bar" |
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| − | "foobar" |
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| − | </haskell> |
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| − | |||
| − | == Numbers == |
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| − | Numbers in Haskell can be of the type <hask>Int, Integer, Float, Double, or Rational</hask>. |
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| − | === Random Numbers === |
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| − | |||
| − | == Dates and Time == |
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| − | Use [http://haskell.org/ghc/docs/latest/html/libraries/base/System-Time.html#v%3AgetClockTime System.Time.getClockTime] to get a properly formatted date stamp. |
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| − | |||
| − | <haskell> |
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| − | Prelude> System.Time.getClockTime |
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| − | Wed Feb 21 20:05:35 CST 2007 |
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| − | </haskell> |
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| − | |||
| − | == Lists == |
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| − | Haskell has all of the general list manipulation functions. |
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| − | |||
| − | <haskell> |
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| − | Prelude> head [1,2,3] |
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| − | 1 |
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| − | |||
| − | Prelude> tail [1,2,3] |
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| − | [2,3] |
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| − | |||
| − | Prelude> length [1,2,3] |
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| − | 3 |
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| − | </haskell> |
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| − | |||
| − | == Pattern Matching == |
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| − | Haskell does implicit pattern matching. |
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| − | |||
| − | A good example of pattern matching is done in the fact function for finding a factorial. |
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| − | <haskell> |
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| − | fact :: Integer -> Integer |
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| − | fact 0 = 1 |
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| − | fact n = n * fact (n - 1) |
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| − | </haskell> |
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| − | In this function, <hask>fact :: Integer -> Integer</hask> is the functions type definition. |
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| − | |||
| − | The next line, <hask>fact 0 = 1</hask> is a pattern match, so when the argument to the function fact is 0, the return value is 1. |
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| − | |||
| − | The 3rd and final line of this function is another pattern match, which says that, whatever number was entered as the argument, is multiplied by the factorial of that number, minus 1. Notice this function is recursive. |
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| − | |||
| − | Pattern matching in Haskell evaluates the patterns in the order they are written, so <hask>fact 0 = 1</hask> is evaluated before <hask>fact n = n * fact (n - 1)</hask>. |
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| − | |||
| − | == Arrays == |
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| − | |||
| − | |||
| − | == Files == |
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| − | === Reading from files === |
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| − | === Writing to files === |
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| − | === Creating new files === |
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| − | |||
| − | |||
| − | == Network Programming == |
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| − | |||
| − | |||
| − | == XML == |
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| − | === Parsing XML === |
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| − | |||
| − | |||
| − | == Databases == |
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| − | === MySQL === |
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| − | === PostgreSQL === |
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| − | === SQLite === |
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| − | |||
| − | |||
| − | == FFI == |
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| − | === How to interface with C=== |
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Latest revision as of 18:49, 26 May 2011
Haskell Cookbook
- Haskell compilers and interpreters
- Numbers
- Lists and strings
- Other data structures
- Dates and time
- Pattern matching
- Interactivity
- Files
- Network programming
- XML
- Databases access
- Graphical user interfaces
- PDF files
- FFI
- Testing