Difference between revisions of "PreludeTour"
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− | = A Tour of the Haskell Prelude = |
+ | == A Tour of the Haskell Prelude == |
+ | |||
+ | |||
+ | ;'''abs''': |
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+ | {| border="0" cellpadding="4" |
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+ | |- |
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+ | | ''type:'' || <hask>abs :: Num a => a -> a</hask> |
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+ | |- |
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+ | | ''description:'' || returns the absolute value of a number. |
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+ | |- |
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+ | | ''definition:'' |
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+ | | <haskell> |
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+ | abs x |
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+ | | x >= 0 = x |
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+ | | otherwise = -x |
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+ | </haskell> |
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+ | |- |
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+ | | ''usage:'' |
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+ | | <pre> |
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+ | Prelude> abs (-3) |
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+ | 3 |
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+ | </pre> |
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+ | |} |
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+ | |||
+ | ;'''all''': |
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+ | {| border="0" cellpadding="4" |
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+ | |- |
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+ | | ''type:'' || <hask>all :: (a -> Bool) -> [a] -> Bool</hask> |
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+ | |- |
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+ | | ''description:'' || pplied to a predicate and a list, returns True if all elements of the list satisfy the predicate, and False otherwise. Similar to the function any. |
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+ | |- |
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+ | | ''definition:'' |
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+ | | <haskell> |
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+ | all p xs = and (map p xs) |
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+ | </haskell> |
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+ | |- |
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+ | | ''usage:'' |
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+ | | <pre> |
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+ | Prelude> all (<11) [1..10] |
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+ | True |
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+ | Prelude> all isDigit "123abc" |
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+ | False |
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+ | </pre> |
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+ | |} |
Revision as of 13:21, 26 October 2009
A Tour of the Haskell Prelude
- abs
type: | abs :: Num a => a -> a
|
description: | returns the absolute value of a number. |
definition: | abs x
| x >= 0 = x
| otherwise = -x
|
usage: | Prelude> abs (-3) 3 |
- all
type: | all :: (a -> Bool) -> [a] -> Bool
|
description: | pplied to a predicate and a list, returns True if all elements of the list satisfy the predicate, and False otherwise. Similar to the function any. |
definition: | all p xs = and (map p xs)
|
usage: | Prelude> all (<11) [1..10] True Prelude> all isDigit "123abc" False |