(a -> b) -> m a -> m b
This function may be used as a value for fmap in a Functor instance.
An infix synonym for fmap.
Lift a function to actions. This function may be used as a value for fmap in a Functor instance.
Promote a function to a monad.
O(n). Map a function over all values in the map.
> map (++ "x") (fromList [(5,"a"), (3,"b")]) == fromList [(3, "bx"), (5, "ax")]
mapMonotonic f s == map f s, but works only when f is monotonic. The precondition is not checked. Semi-formally, we have:
> and [x < y ==> f x < f y | x <- ls, y <- ls]
> ==> mapMonotonic f s == map f s
map f xs is the list obtained by applying f to each element of xs, i.e.,
> map f [x1, x2, ..., xn] == [f x1, f x2, ..., f xn]
> map f [x1, x2, ...] == [f x1, f x2, ...]
In many situations, the liftM operations can be replaced by uses of ap, which promotes function application.
> return f `ap` x1 `ap` ... `ap` xn
is equivalent to
> liftMn f x1 x2 ... xn
A variant of <*> with the arguments reversed.
O(n*log n). map f s is the set obtained by applying f to each element of s.
It's worth noting that the size of the result may be smaller if, for some (x,y), x /= y && f x == f y
A combination of parList and map, encapsulating a common pattern:
> parMap strat f = withStrategy (parList strat) . map f
Application operator. This operator is redundant, since ordinary application (f x) means the same as (f $ x). However, $ has low, right-associative binding precedence, so it sometimes allows parentheses to be omitted; for example:
> f $ g $ h x = f (g (h x))
It is also useful in higher-order situations, such as map ($ 0) xs, or Data.List.zipWith ($) fs xs.
Strict (call-by-value) application, defined in terms of seq.
O(log(min(i,n-i))). Update the element at the specified position. If the position is out of range, the original sequence is returned.
This function may be used as a value for Data.Foldable.foldMap in a Foldable instance.
O(min(n,W)). Adjust a value at a specific key. When the key is not a member of the map, the original map is returned.
> adjust ("new " ++) 5 (fromList [(5,"a"), (3,"b")]) == fromList [(3, "b"), (5, "new a")]
> adjust ("new " ++) 7 (fromList [(5,"a"), (3,"b")]) == fromList [(3, "b"), (5, "a")]
> adjust ("new " ++) 7 empty == empty
The maybe function takes a default value, a function, and a Maybe value. If the Maybe value is Nothing, the function returns the default value. Otherwise, it applies the function to the value inside the Just and returns the result.
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