Difference between revisions of "Cookbook/Interactivity"

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= Reading a string =
 +
== Input and output ==
⚫
Strings can be read as input using [http://haskell.org/ghc/docs/latest/html/libraries/base/Prelude.html#v%3AgetLine getLine].
  
⚫
<haskell>
  
⚫
Prelude> getLine
  
−
Foo bar baz
  
−
"Foo bar baz"
  
⚫
</haskell>
  
   
  +
{| class="wikitable"
⚫
= Printing a string =
  
  +
|-
−
Strings can be output in a number of different ways.
  
  +
! Problem
⚫
<haskell>
  
  +
! Solution
  +
! Examples
  +
|-
  +
| printing a string
  +
| [http://haskell.org/ghc/docs/latest/html/libraries/base/Prelude.html#v%3AputStr putStr]
  ⚫
|<haskell>
 
Prelude> putStr "Foo"
  
Prelude> putStr "Foo"
 
FooPrelude>
  
FooPrelude>
 
</haskell>
  
</haskell>
  +
|-
⚫
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:
  
  +
| printing a string with a newline character
−
<haskell>
  
  ⚫
| [http://haskell.org/ghc/docs/latest/html/libraries/base/Prelude.html#v%3AputStrLn putStrLn]
−
Prelude> putStr "Foo\n"
  
  ⚫
|<haskell>
−
Foo
  
−
</haskell>
  
⚫
Or use [http://haskell.org/ghc/docs/latest/html/libraries/base/Prelude.html#v%3AputStrLn putStrLn], which is already in the Standard Prelude
  
−
<haskell>
  
 
Prelude> putStrLn "Foo"
  
Prelude> putStrLn "Foo"
 
Foo
  
Foo
  +
Prelude>
 
</haskell>
  
</haskell>
  +
|-
−
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.'''
  
  ⚫
| reading a string
−
<haskell>
  
  ⚫
| [http://haskell.org/ghc/docs/latest/html/libraries/base/Prelude.html#v%3AgetLine getLine]
−
Prelude> print "Foo"
  
  ⚫
|<haskell>
−
"Foo"
  
  ⚫
Prelude> getLine
  +
Foo bar baz --> "Foo bar baz"
 
</haskell>
  
</haskell>
  +
|}
  +
  +
   
−
= Parsing command line arguments =
 +
== Parsing command line arguments ==
   
 
TODO
  
TODO

Revision as of 09:08, 2 August 2009

Input and output

Problem Solution Examples
printing a string putStr 
Prelude> putStr "Foo"
FooPrelude>
printing a string with a newline character putStrLn 
Prelude> putStrLn "Foo"
Foo
Prelude>
reading a string getLine 
Prelude> getLine
Foo bar baz          --> "Foo bar baz"


Parsing command line arguments

TODO

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