Difference between revisions of "Cookbook/Interactivity"

From HaskellWiki
Jump to navigation Jump to search
(4 intermediate revisions by the same user not shown)
Line 1: Line 1:
  +
== Input and output ==
  +
 
{| class="wikitable"
  
{| class="wikitable"
 
|-
  
|-
Line 5: Line 7:
 
! Examples
  
! Examples
 
|-
  
|-
−
| reading a string
 +
| printing a string
−
| [http://haskell.org/ghc/docs/latest/html/libraries/base/Prelude.html#v%3AgetLine getLine]
 +
| [http://haskell.org/ghc/docs/latest/html/libraries/base/Prelude.html#v%3AputStr putStr]
 
|<haskell>
  
|<haskell>
⚫
Prelude> getLine
  
⚫
Foo bar baz --> "Foo bar baz"
  
⚫
</haskell>
  
⚫
|}
  
−  
⚫
== Printing a string ==
  
−
Strings can be output in a number of different ways.
  
⚫
<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 ==

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

Retrieved from "https://wiki.haskell.org/index.php?title=Cookbook/Interactivity&oldid=29397"