Class of immutable vectors. Every immutable vector is associated with its mutable version through the Mutable type family. Methods of this class should not be used directly. Instead, Data.Vector.Generic and other Data.Vector modules provide safe and fusible wrappers.

Minimum complete implementation:

• basicUnsafeFreeze
• basicUnsafeThaw
• basicLength
• basicUnsafeSlice
• basicUnsafeIndexM

Mutable v s a is the mutable version of the pure vector type v a with the state token s. It is injective on GHC 8 and newer.

O(1) Yield the length of the vector

O(1) Test whether a vector is empty

O(1) Indexing

O(1) Safe indexing

O(1) First element

O(1) Last element

O(1) Unsafe indexing without bounds checking

O(1) First element without checking if the vector is empty

O(1) Last element without checking if the vector is empty

O(1) Indexing in a monad.

The monad allows operations to be strict in the vector when necessary. Suppose vector copying is implemented like this:

copy mv v = ... write mv i (v ! i) ...

For lazy vectors, v ! i would not be evaluated which means that mv would unnecessarily retain a reference to v in each element written.

With indexM, copying can be implemented like this instead:

copy mv v = ... do
                  x <- indexM v i
                  write mv i x

Here, no references to v are retained because indexing (but not the elements) is evaluated eagerly.

O(1) First element of a vector in a monad. See indexM for an explanation of why this is useful.

O(1) Last element of a vector in a monad. See indexM for an explanation of why this is useful.

O(1) Indexing in a monad without bounds checks. See indexM for an explanation of why this is useful.

O(1) First element in a monad without checking for empty vectors. See indexM for an explanation of why this is useful.

O(1) Last element in a monad without checking for empty vectors. See indexM for an explanation of why this is useful.

O(1) Yield a slice of the vector without copying it. The vector must contain at least i+n elements.

O(1) Yield all but the last element without copying. The vector may not be empty.

O(1) Yield all but the first element without copying. The vector may not be empty.

O(1) Yield the first n elements without copying. The vector may contain less than n elements in which case it is returned unchanged.

O(1) Yield all but the first n elements without copying. The vector may contain less than n elements in which case an empty vector is returned.

O(1) Yield the first n elements paired with the remainder without copying.

Note that splitAt n v is equivalent to (take n v, drop n v) but slightly more efficient.

Since: 0.7.1

O(1) Yield the head and tail of the vector, or Nothing if empty.

Since: 0.12.2.0

O(1) Yield the last and init of the vector, or Nothing if empty.

Since: 0.12.2.0

O(1) Yield a slice of the vector without copying. The vector must contain at least i+n elements but this is not checked.

O(1) Yield all but the last element without copying. The vector may not be empty but this is not checked.

O(1) Yield all but the first element without copying. The vector may not be empty but this is not checked.

O(1) Yield the first n elements without copying. The vector must contain at least n elements but this is not checked.

O(1) Yield all but the first n elements without copying. The vector must contain at least n elements but this is not checked.

O(1) Empty vector

O(1) Vector with exactly one element

O(n) Vector of the given length with the same value in each position

O(n) Construct a vector of the given length by applying the function to each index

O(n) Apply function \(\max(n - 1, 0)\) times to an initial value, producing a vector of length \(\max(n, 0)\). Zeroth element will contain the initial value, that's why there is one less function application than the number of elements in the produced vector.

\( \underbrace{x, f (x), f (f (x)), \ldots}_{\max(0,n)\rm{~elements}} \)

Since: 0.7.1

O(n) Execute the monadic action the given number of times and store the results in a vector.

O(n) Construct a vector of the given length by applying the monadic action to each index

O(n) Apply monadic function \(\max(n - 1, 0)\) times to an initial value, producing a vector of length \(\max(n, 0)\). Zeroth element will contain the initial value, that's why there is one less function application than the number of elements in the produced vector.

For non-monadic version see iterateN

Since: 0.12.0.0

Execute the monadic action and freeze the resulting vector.

create (do { v <- new 2; write v 0 'a'; write v 1 'b'; return v }) = <a,b>

Execute the monadic action and freeze the resulting vectors.

O(n) Construct a vector by repeatedly applying the generator function to a seed. The generator function yields Just the next element and the new seed or Nothing if there are no more elements.

unfoldr (\n -> if n == 0 then Nothing else Just (n,n-1)) 10
 = <10,9,8,7,6,5,4,3,2,1>

O(n) Construct a vector with at most n elements by repeatedly applying the generator function to a seed. The generator function yields Just the next element and the new seed or Nothing if there are no more elements.

unfoldrN 3 (\n -> Just (n,n-1)) 10 = <10,9,8>

O(n) Construct a vector with exactly n elements by repeatedly applying the generator function to a seed. The generator function yields the next element and the new seed.

unfoldrExactN 3 (\n -> (n,n-1)) 10 = <10,9,8>

Since: 0.12.2.0

O(n) Construct a vector by repeatedly applying the monadic generator function to a seed. The generator function yields Just the next element and the new seed or Nothing if there are no more elements.

O(n) Construct a vector by repeatedly applying the monadic generator function to a seed. The generator function yields Just the next element and the new seed or Nothing if there are no more elements.

O(n) Construct a vector with exactly n elements by repeatedly applying the monadic generator function to a seed. The generator function yields the next element and the new seed.

Since: 0.12.2.0

O(n) Construct a vector with n elements by repeatedly applying the generator function to the already constructed part of the vector.

constructN 3 f = let a = f <> ; b = f <a> ; c = f <a,b> in <a,b,c>

O(n) Construct a vector with n elements from right to left by repeatedly applying the generator function to the already constructed part of the vector.

constructrN 3 f = let a = f <> ; b = f<a> ; c = f <b,a> in <c,b,a>

O(n) Yield a vector of the given length containing the values x, x+1 etc. This operation is usually more efficient than enumFromTo.

enumFromN 5 3 = <5,6,7>

O(n) Yield a vector of the given length containing the values x, x+y, x+y+y etc. This operations is usually more efficient than enumFromThenTo.

enumFromStepN 1 0.1 5 = <1,1.1,1.2,1.3,1.4>

O(n) Enumerate values from x to y.

WARNING: This operation can be very inefficient. If at all possible, use enumFromN instead.

O(n) Enumerate values from x to y with a specific step z.

WARNING: This operation can be very inefficient. If at all possible, use enumFromStepN instead.

O(n) Prepend an element

O(n) Append an element

O(m+n) Concatenate two vectors

O(n) Concatenate all vectors in the list

O(n) Concatenate all vectors in the non-empty list

O(n) Yield the argument but force it not to retain any extra memory, possibly by copying it.

This is especially useful when dealing with slices. For example:

force (slice 0 2 <huge vector>)

Here, the slice retains a reference to the huge vector. Forcing it creates a copy of just the elements that belong to the slice and allows the huge vector to be garbage collected.

O(m+n) For each pair (i,a) from the list, replace the vector element at position i by a.

<5,9,2,7> // [(2,1),(0,3),(2,8)] = <3,9,8,7>

O(m+n) For each pair (i,a) from the vector of index/value pairs, replace the vector element at position i by a.

update <5,9,2,7> <(2,1),(0,3),(2,8)> = <3,9,8,7>

O(m+min(n1,n2)) For each index i from the index vector and the corresponding value a from the value vector, replace the element of the initial vector at position i by a.

update_ <5,9,2,7>  <2,0,2> <1,3,8> = <3,9,8,7>

This function is useful for instances of Vector that cannot store pairs. Otherwise, update is probably more convenient.

update_ xs is ys = update xs (zip is ys)

Same as (//) but without bounds checking.

Same as update but without bounds checking.

Same as update_ but without bounds checking.

O(m+n) For each pair (i,b) from the list, replace the vector element a at position i by f a b.

Examples

>>> import qualified Data.Vector as V
>>> V.accum (+) (V.fromList [1000.0,2000.0,3000.0]) [(2,4),(1,6),(0,3),(1,10)]
[1003.0,2016.0,3004.0]

O(m+n) For each pair (i,b) from the vector of pairs, replace the vector element a at position i by f a b.

Examples

>>> import qualified Data.Vector as V
>>> V.accumulate (+) (V.fromList [1000.0,2000.0,3000.0]) (V.fromList [(2,4),(1,6),(0,3),(1,10)])
[1003.0,2016.0,3004.0]

O(m+min(n1,n2)) For each index i from the index vector and the corresponding value b from the the value vector, replace the element of the initial vector at position i by f a b.

accumulate_ (+) <5,9,2> <2,1,0,1> <4,6,3,7> = <5+3, 9+6+7, 2+4>

This function is useful for instances of Vector that cannot store pairs. Otherwise, accumulate is probably more convenient:

accumulate_ f as is bs = accumulate f as (zip is bs)

Same as accum but without bounds checking.

Same as accumulate but without bounds checking.

Same as accumulate_ but without bounds checking.

O(n) Reverse a vector

O(n) Yield the vector obtained by replacing each element i of the index vector by xs!i. This is equivalent to map (xs!) is but is often much more efficient.

backpermute <a,b,c,d> <0,3,2,3,1,0> = <a,d,c,d,b,a>

Same as backpermute but without bounds checking.

Apply a destructive operation to a vector. The operation will be performed in place if it is safe to do so and will modify a copy of the vector otherwise.

modify (\v -> write v 0 'x') (replicate 3 'a') = <'x','a','a'>

O(n) Pair each element in a vector with its index

O(n) Map a function over a vector

O(n) Apply a function to every element of a vector and its index

Map a function over a vector and concatenate the results.

O(n) Apply the monadic action to all elements of the vector, yielding a vector of results

O(n) Apply the monadic action to every element of a vector and its index, yielding a vector of results

O(n) Apply the monadic action to all elements of a vector and ignore the results

O(n) Apply the monadic action to every element of a vector and its index, ignoring the results

O(n) Apply the monadic action to all elements of the vector, yielding a vector of results. Equivalent to flip mapM.

O(n) Apply the monadic action to all elements of a vector and ignore the results. Equivalent to flip mapM_.

O(n) Apply the monadic action to all elements of the vector and their indices, yielding a vector of results. Equivalent to flip imapM.

Since: 0.12.2.0

O(n) Apply the monadic action to all elements of the vector and their indices and ignore the results. Equivalent to flip imapM_.

Since: 0.12.2.0

O(min(m,n)) Zip two vectors with the given function.

Zip three vectors with the given function.

O(min(m,n)) Zip two vectors with a function that also takes the elements' indices.

O(min(m,n)) Zip two vectors

O(min(m,n)) Zip the two vectors with the monadic action and yield a vector of results

O(min(m,n)) Zip the two vectors with a monadic action that also takes the element index and yield a vector of results

O(min(m,n)) Zip the two vectors with the monadic action and ignore the results

O(min(m,n)) Zip the two vectors with a monadic action that also takes the element index and ignore the results

O(min(m,n)) Unzip a vector of pairs.

O(n) Drop elements that do not satisfy the predicate

O(n) Drop elements that do not satisfy the predicate which is applied to values and their indices

O(n) Drop elements that do not satisfy the monadic predicate

O(n) Drop repeated adjacent elements.

O(n) Drop elements when predicate returns Nothing

O(n) Drop elements when predicate, applied to index and value, returns Nothing

O(n) Apply monadic function to each element of vector and discard elements returning Nothing.

Since: 0.12.2.0

O(n) Apply monadic function to each element of vector and its index. Discards elements returning Nothing.

Since: 0.12.2.0

O(n) Yield the longest prefix of elements satisfying the predicate. Current implementation is not copy-free, unless the result vector is fused away.

O(n) Drop the longest prefix of elements that satisfy the predicate without copying.

O(n) Split the vector in two parts, the first one containing those elements that satisfy the predicate and the second one those that don't. The relative order of the elements is preserved at the cost of a sometimes reduced performance compared to unstablePartition.

O(n) Split the vector into two parts, the first one containing the Left elements and the second containing the Right elements. The relative order of the elements is preserved.

Since: 0.12.1.0

O(n) Split the vector in two parts, the first one containing those elements that satisfy the predicate and the second one those that don't. The order of the elements is not preserved but the operation is often faster than partition.

O(n) Split the vector into the longest prefix of elements that satisfy the predicate and the rest without copying.

O(n) Split the vector into the longest prefix of elements that do not satisfy the predicate and the rest without copying.

O(n) Check if the vector contains an element

O(n) Check if the vector does not contain an element (inverse of elem)

O(n) Yield Just the first element matching the predicate or Nothing if no such element exists.

O(n) Yield Just the index of the first element matching the predicate or Nothing if no such element exists.

O(n) Yield Just the index of the last element matching the predicate or Nothing if no such element exists.

Since: 0.12.2.0

O(n) Yield the indices of elements satisfying the predicate in ascending order.

O(n) Yield Just the index of the first occurence of the given element or Nothing if the vector does not contain the element. This is a specialised version of findIndex.

O(n) Yield the indices of all occurences of the given element in ascending order. This is a specialised version of findIndices.

O(n) Left fold

O(n) Left fold on non-empty vectors

O(n) Left fold with strict accumulator

O(n) Left fold on non-empty vectors with strict accumulator

O(n) Right fold

O(n) Right fold on non-empty vectors

O(n) Right fold with a strict accumulator

O(n) Right fold on non-empty vectors with strict accumulator

O(n) Left fold (function applied to each element and its index)

O(n) Left fold with strict accumulator (function applied to each element and its index)

O(n) Right fold (function applied to each element and its index)

O(n) Right fold with strict accumulator (function applied to each element and its index)

O(n) Map each element of the structure to a monoid, and combine the results. It uses same implementation as corresponding method of Foldable type cless. Note it's implemented in terms of foldr and won't fuse with functions that traverse vector from left to right (map, generate, etc.).

Since: 0.12.2.0

O(n) foldMap which is strict in accumulator. It uses same implementation as corresponding method of Foldable type class. Note it's implemented in terms of foldl' so it fuses in most contexts.

Since: 0.12.2.0

O(n) Check if all elements satisfy the predicate.

Examples

>>> import qualified Data.Vector as V
>>> V.all even $ V.fromList [2, 4, 12 :: Int]
True
>>> V.all even $ V.fromList [2, 4, 13 :: Int]
False
>>> V.all even (V.empty :: V.Vector Int)
True

O(n) Check if any element satisfies the predicate.

Examples

>>> import qualified Data.Vector as V
>>> V.any even $ V.fromList [1, 3, 7 :: Int]
False
>>> V.any even $ V.fromList [3, 2, 13 :: Int]
True
>>> V.any even (V.empty :: V.Vector Int)
False

O(n) Check if all elements are True

Examples

>>> import qualified Data.Vector as V
>>> V.and $ V.fromList [True, False]
False
>>> V.and V.empty
True

O(n) Check if any element is True

Examples

>>> import qualified Data.Vector as V
>>> V.or $ V.fromList [True, False]
True
>>> V.or V.empty
False

O(n) Compute the sum of the elements

Examples

>>> import qualified Data.Vector as V
>>> V.sum $ V.fromList [300,20,1 :: Int]
321
>>> V.sum (V.empty :: V.Vector Int)
0

O(n) Compute the produce of the elements

Examples

>>> import qualified Data.Vector as V
>>> V.product $ V.fromList [1,2,3,4 :: Int]
24
>>> V.product (V.empty :: V.Vector Int)
1

O(n) Yield the maximum element of the vector. The vector may not be empty.

Examples

>>> import qualified Data.Vector as V
>>> V.maximum $ V.fromList [2.0, 1.0]
2.0

O(n) Yield the maximum element of the vector according to the given comparison function. The vector may not be empty.

O(n) Yield the minimum element of the vector. The vector may not be empty.

Examples

>>> import qualified Data.Vector as V
>>> V.minimum $ V.fromList [2.0, 1.0]
1.0

O(n) Yield the minimum element of the vector according to the given comparison function. The vector may not be empty.

O(n) Yield the index of the minimum element of the vector. The vector may not be empty.

O(n) Yield the index of the minimum element of the vector according to the given comparison function. The vector may not be empty.

O(n) Yield the index of the maximum element of the vector. The vector may not be empty.

O(n) Yield the index of the maximum element of the vector according to the given comparison function. The vector may not be empty.

O(n) Monadic fold

O(n) Monadic fold (action applied to each element and its index)

O(n) Monadic fold with strict accumulator

O(n) Monadic fold with strict accumulator (action applied to each element and its index)

O(n) Monadic fold over non-empty vectors

O(n) Monadic fold over non-empty vectors with strict accumulator

O(n) Monadic fold that discards the result

O(n) Monadic fold that discards the result (action applied to each element and its index)

O(n) Monadic fold with strict accumulator that discards the result

O(n) Monadic fold with strict accumulator that discards the result (action applied to each element and its index)

O(n) Monadic fold over non-empty vectors that discards the result

O(n) Monad fold over non-empty vectors with strict accumulator that discards the result

Evaluate each action and collect the results

Evaluate each action and discard the results

O(n) Prescan

prescanl f z = init . scanl f z

Example: prescanl (+) 0 <1,2,3,4> = <0,1,3,6>

O(n) Prescan with strict accumulator

O(n) Scan

postscanl f z = tail . scanl f z

Example: postscanl (+) 0 <1,2,3,4> = <1,3,6,10>

O(n) Scan with strict accumulator

O(n) Haskell-style scan

scanl f z <x1,...,xn> = <y1,...,y(n+1)>
  where y1 = z
        yi = f y(i-1) x(i-1)

Example: scanl (+) 0 <1,2,3,4> = <0,1,3,6,10>

O(n) Haskell-style scan with strict accumulator

O(n) Scan over a non-empty vector

scanl f <x1,...,xn> = <y1,...,yn>
  where y1 = x1
        yi = f y(i-1) xi

O(n) Scan over a non-empty vector with a strict accumulator

O(n) Scan over a vector with its index

O(n) Scan over a vector (strictly) with its index

O(n) Right-to-left prescan

prescanr f z = reverse . prescanl (flip f) z . reverse

O(n) Right-to-left prescan with strict accumulator

O(n) Right-to-left scan

O(n) Right-to-left scan with strict accumulator

O(n) Right-to-left Haskell-style scan

O(n) Right-to-left Haskell-style scan with strict accumulator

O(n) Right-to-left scan over a non-empty vector

O(n) Right-to-left scan over a non-empty vector with a strict accumulator

O(n) Right-to-left scan over a vector with its index

O(n) Right-to-left scan over a vector (strictly) with its index

O(n) Convert a vector to a list

O(n) Convert a list to a vector

O(n) Convert the first n elements of a list to a vector

fromListN n xs = fromList (take n xs)

Examples

>>> import qualified Data.Vector as V
>>> V.fromListN 3 [1,2,3,4,5::Int]
[1,2,3]
>>> V.fromListN 3 [1::Int]
[1]

O(n) Convert different vector types

O(n) Yield an immutable copy of the mutable vector.

O(n) Yield a mutable copy of the immutable vector.

O(n) Copy an immutable vector into a mutable one. The two vectors must have the same length.

O(1) Unsafe convert a mutable vector to an immutable one without copying. The mutable vector may not be used after this operation.

O(1) Unsafely convert an immutable vector to a mutable one without copying. Note that this is very dangerous function and generally it's only safe to read from resulting vector. In which case immutable vector could be used safely as well.

Problem with mutation happens because GHC has a lot of freedom to introduce sharing. As a result mutable vectors produced by unsafeThaw may or may not share same underlying buffer. For example:

foo = do
  let vec = V.generate 10 id
  mvec <- V.unsafeThaw vec
  do_something mvec

Here GHC could lift vec outside of foo which means all calls to do_something will use same buffer with possibly disastrous results. Whether such aliasing happens or not depends on program in question, optimization levels, and GHC flags.

All in all attempts to modify vector after unsafeThaw falls out of domain of software engineering and into realm of black magic, dark rituals, and unspeakable horrors. Only advice that could be given is: "don't attempt to mutate vector after unsafeThaw unless you know how to prevent GHC from aliasing buffers accidentally. We don't"

O(n) Copy an immutable vector into a mutable one. The two vectors must have the same length. This is not checked.

O(1) Convert a vector to a Bundle

O(n) Construct a vector from a Bundle

Load monadic stream bundle into a newly allocated vector. This function goes through a list, so prefer using unstream, unless you need to be in a monad.

Since: 0.12.2.0

O(1) Convert a vector to a Bundle, proceeding from right to left

O(n) Construct a vector from a Bundle, proceeding from right to left

Construct a vector from a monadic initialiser.

Convert a vector to an initialiser which, when run, produces a copy of the vector.

O(n) Check if two vectors are equal. All Vector instances are also instances of Eq and it is usually more appropriate to use those. This function is primarily intended for implementing Eq instances for new vector types.

O(n) Compare two vectors lexicographically. All Vector instances are also instances of Ord and it is usually more appropriate to use those. This function is primarily intended for implementing Ord instances for new vector types.

O(n) Check if two vectors are equal using supplied equality predicate.

O(n) Compare two vectors using supplied comparison function for vector elements. Comparison works same as for lists.

cmpBy compare == cmp

Generic definition of showsPrec

Generic definition of readPrec

Note: uses ReadS

Generic definion of gfoldl that views a Vector as a list.