PreludeTour: Difference between revisions
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== A Tour of the Haskell Prelude == | == A Tour of the Haskell Prelude == | ||
;<span id="abs">'''abs'''</span>: | |||
{| border="0" cellpadding="4" | |||
|- | |||
| ''type:'' || <hask>abs :: Num a => a -> a</hask> | |||
|- | |||
| ''description:'' || returns the absolute value of a number. | |||
|- | |||
| ''definition:'' | |||
| <haskell> | |||
abs x | |||
| x >= 0 = x | |||
| otherwise = -x | |||
</haskell> | |||
|- | |||
| ''usage:'' | |||
| <pre> | |||
Prelude> abs (-3) | |||
3 | |||
</pre> | |||
|} | |||
;<span id="all">'''all'''</span>: | |||
{| border="0" cellpadding="4" | |||
|- | |||
| ''type:'' || <hask>all :: (a -> Bool) -> [a] -> Bool</hask> | |||
|- | |||
| ''description:'' || Applied 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:'' | |||
| <haskell> | |||
all p xs = and (map p xs) | |||
</haskell> | |||
|- | |||
| ''usage:'' | |||
| <pre> | |||
Prelude> all (<11) [1..10] | |||
True | |||
Prelude> all isDigit "123abc" | |||
False | |||
</pre> | |||
|} |
Latest revision as of 15:19, 6 February 2021
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: | Applied 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 |