Copyright | (c) Roman Leshchinskiy 2009-2010 |
---|---|

License | BSD-style |

Maintainer | Roman Leshchinskiy <rl@cse.unsw.edu.au> |

Stability | experimental |

Portability | non-portable |

Safe Haskell | None |

Language | Haskell2010 |

Mutable adaptive unboxed vectors

## Synopsis

- data family MVector s a
- type IOVector = MVector RealWorld
- type STVector s = MVector s
- class (Vector Vector a, MVector MVector a) => Unbox a
- length :: Unbox a => MVector s a -> Int
- null :: Unbox a => MVector s a -> Bool
- slice :: Unbox a => Int -> Int -> MVector s a -> MVector s a
- init :: Unbox a => MVector s a -> MVector s a
- tail :: Unbox a => MVector s a -> MVector s a
- take :: Unbox a => Int -> MVector s a -> MVector s a
- drop :: Unbox a => Int -> MVector s a -> MVector s a
- splitAt :: Unbox a => Int -> MVector s a -> (MVector s a, MVector s a)
- unsafeSlice :: Unbox a => Int -> Int -> MVector s a -> MVector s a
- unsafeInit :: Unbox a => MVector s a -> MVector s a
- unsafeTail :: Unbox a => MVector s a -> MVector s a
- unsafeTake :: Unbox a => Int -> MVector s a -> MVector s a
- unsafeDrop :: Unbox a => Int -> MVector s a -> MVector s a
- overlaps :: Unbox a => MVector s a -> MVector s a -> Bool
- new :: (PrimMonad m, Unbox a) => Int -> m (MVector (PrimState m) a)
- unsafeNew :: (PrimMonad m, Unbox a) => Int -> m (MVector (PrimState m) a)
- replicate :: (PrimMonad m, Unbox a) => Int -> a -> m (MVector (PrimState m) a)
- replicateM :: (PrimMonad m, Unbox a) => Int -> m a -> m (MVector (PrimState m) a)
- generate :: (PrimMonad m, Unbox a) => Int -> (Int -> a) -> m (MVector (PrimState m) a)
- generateM :: (PrimMonad m, Unbox a) => Int -> (Int -> m a) -> m (MVector (PrimState m) a)
- clone :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> m (MVector (PrimState m) a)
- grow :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> Int -> m (MVector (PrimState m) a)
- unsafeGrow :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> Int -> m (MVector (PrimState m) a)
- clear :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> m ()
- zip :: (Unbox a, Unbox b) => MVector s a -> MVector s b -> MVector s (a, b)
- zip3 :: (Unbox a, Unbox b, Unbox c) => MVector s a -> MVector s b -> MVector s c -> MVector s (a, b, c)
- zip4 :: (Unbox a, Unbox b, Unbox c, Unbox d) => MVector s a -> MVector s b -> MVector s c -> MVector s d -> MVector s (a, b, c, d)
- zip5 :: (Unbox a, Unbox b, Unbox c, Unbox d, Unbox e) => MVector s a -> MVector s b -> MVector s c -> MVector s d -> MVector s e -> MVector s (a, b, c, d, e)
- zip6 :: (Unbox a, Unbox b, Unbox c, Unbox d, Unbox e, Unbox f) => MVector s a -> MVector s b -> MVector s c -> MVector s d -> MVector s e -> MVector s f -> MVector s (a, b, c, d, e, f)
- unzip :: (Unbox a, Unbox b) => MVector s (a, b) -> (MVector s a, MVector s b)
- unzip3 :: (Unbox a, Unbox b, Unbox c) => MVector s (a, b, c) -> (MVector s a, MVector s b, MVector s c)
- unzip4 :: (Unbox a, Unbox b, Unbox c, Unbox d) => MVector s (a, b, c, d) -> (MVector s a, MVector s b, MVector s c, MVector s d)
- unzip5 :: (Unbox a, Unbox b, Unbox c, Unbox d, Unbox e) => MVector s (a, b, c, d, e) -> (MVector s a, MVector s b, MVector s c, MVector s d, MVector s e)
- unzip6 :: (Unbox a, Unbox b, Unbox c, Unbox d, Unbox e, Unbox f) => MVector s (a, b, c, d, e, f) -> (MVector s a, MVector s b, MVector s c, MVector s d, MVector s e, MVector s f)
- read :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> Int -> m a
- write :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> Int -> a -> m ()
- modify :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> (a -> a) -> Int -> m ()
- modifyM :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> (a -> m a) -> Int -> m ()
- swap :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> Int -> Int -> m ()
- exchange :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> Int -> a -> m a
- unsafeRead :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> Int -> m a
- unsafeWrite :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> Int -> a -> m ()
- unsafeModify :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> (a -> a) -> Int -> m ()
- unsafeModifyM :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> (a -> m a) -> Int -> m ()
- unsafeSwap :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> Int -> Int -> m ()
- unsafeExchange :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> Int -> a -> m a
- mapM_ :: (PrimMonad m, Unbox a) => (a -> m b) -> MVector (PrimState m) a -> m ()
- imapM_ :: (PrimMonad m, Unbox a) => (Int -> a -> m b) -> MVector (PrimState m) a -> m ()
- forM_ :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> (a -> m b) -> m ()
- iforM_ :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> (Int -> a -> m b) -> m ()
- foldl :: (PrimMonad m, Unbox a) => (b -> a -> b) -> b -> MVector (PrimState m) a -> m b
- foldl' :: (PrimMonad m, Unbox a) => (b -> a -> b) -> b -> MVector (PrimState m) a -> m b
- foldM :: (PrimMonad m, Unbox a) => (b -> a -> m b) -> b -> MVector (PrimState m) a -> m b
- foldM' :: (PrimMonad m, Unbox a) => (b -> a -> m b) -> b -> MVector (PrimState m) a -> m b
- foldr :: (PrimMonad m, Unbox a) => (a -> b -> b) -> b -> MVector (PrimState m) a -> m b
- foldr' :: (PrimMonad m, Unbox a) => (a -> b -> b) -> b -> MVector (PrimState m) a -> m b
- foldrM :: (PrimMonad m, Unbox a) => (a -> b -> m b) -> b -> MVector (PrimState m) a -> m b
- foldrM' :: (PrimMonad m, Unbox a) => (a -> b -> m b) -> b -> MVector (PrimState m) a -> m b
- ifoldl :: (PrimMonad m, Unbox a) => (b -> Int -> a -> b) -> b -> MVector (PrimState m) a -> m b
- ifoldl' :: (PrimMonad m, Unbox a) => (b -> Int -> a -> b) -> b -> MVector (PrimState m) a -> m b
- ifoldM :: (PrimMonad m, Unbox a) => (b -> Int -> a -> m b) -> b -> MVector (PrimState m) a -> m b
- ifoldM' :: (PrimMonad m, Unbox a) => (b -> Int -> a -> m b) -> b -> MVector (PrimState m) a -> m b
- ifoldr :: (PrimMonad m, Unbox a) => (Int -> a -> b -> b) -> b -> MVector (PrimState m) a -> m b
- ifoldr' :: (PrimMonad m, Unbox a) => (Int -> a -> b -> b) -> b -> MVector (PrimState m) a -> m b
- ifoldrM :: (PrimMonad m, Unbox a) => (Int -> a -> b -> m b) -> b -> MVector (PrimState m) a -> m b
- ifoldrM' :: (PrimMonad m, Unbox a) => (Int -> a -> b -> m b) -> b -> MVector (PrimState m) a -> m b
- nextPermutation :: (PrimMonad m, Ord e, Unbox e) => MVector (PrimState m) e -> m Bool
- set :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> a -> m ()
- copy :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> MVector (PrimState m) a -> m ()
- move :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> MVector (PrimState m) a -> m ()
- unsafeCopy :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> MVector (PrimState m) a -> m ()
- unsafeMove :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> MVector (PrimState m) a -> m ()

# Mutable vectors of primitive types

data family MVector s a Source #

#### Instances

class (Vector Vector a, MVector MVector a) => Unbox a Source #

#### Instances

# Accessors

## Length information

## Extracting subvectors

Yield a part of the mutable vector without copying it. The vector must
contain at least `i+n`

elements.

init :: Unbox a => MVector s a -> MVector s a Source #

Drop last element of the mutable vector without making a copy. If vector is empty exception is thrown.

tail :: Unbox a => MVector s a -> MVector s a Source #

Drop first element of the mutable vector without making a copy. If vector is empty exception is thrown.

take :: Unbox a => Int -> MVector s a -> MVector s a Source #

Take `n`

first elements of the mutable vector without making a
copy. For negative `n`

empty vector is returned. If `n`

is larger
than vector's length empty vector is returned,

drop :: Unbox a => Int -> MVector s a -> MVector s a Source #

Drop `n`

first element of the mutable vector without making a
copy. For negative `n`

vector is returned unchanged and if `n`

is
larger than vector's length empty vector is returned.

Yield a part of the mutable vector without copying it. No bounds checks are performed.

unsafeInit :: Unbox a => MVector s a -> MVector s a Source #

Same as `init`

but doesn't do range checks.

unsafeTail :: Unbox a => MVector s a -> MVector s a Source #

Same as `tail`

but doesn't do range checks.

unsafeTake :: Unbox a => Int -> MVector s a -> MVector s a Source #

Unsafe variant of `take`

. If called with out of range `n`

it will
simply create invalid slice that likely violate memory safety

unsafeDrop :: Unbox a => Int -> MVector s a -> MVector s a Source #

Unsafe variant of `drop`

. If called with out of range `n`

it will
simply create invalid slice that likely violate memory safety

## Overlapping

overlaps :: Unbox a => MVector s a -> MVector s a -> Bool Source #

Check whether two vectors overlap.

# Construction

## Initialisation

new :: (PrimMonad m, Unbox a) => Int -> m (MVector (PrimState m) a) Source #

Create a mutable vector of the given length.

unsafeNew :: (PrimMonad m, Unbox a) => Int -> m (MVector (PrimState m) a) Source #

Create a mutable vector of the given length. The vector content is uninitialized, which means it is filled with whatever underlying memory buffer happens to contain.

*Since: 0.5*

replicate :: (PrimMonad m, Unbox a) => Int -> a -> m (MVector (PrimState m) a) Source #

Create a mutable vector of the given length (0 if the length is negative) and fill it with an initial value.

replicateM :: (PrimMonad m, Unbox a) => Int -> m a -> m (MVector (PrimState m) a) Source #

Create a mutable vector of the given length (0 if the length is negative) and fill it with values produced by repeatedly executing the monadic action.

generate :: (PrimMonad m, Unbox a) => Int -> (Int -> a) -> m (MVector (PrimState m) a) Source #

*O(n)* Create a mutable vector of the given length (0 if the length is negative)
and fill it with the results of applying the function to each index.

*Since: 0.12.3.0*

generateM :: (PrimMonad m, Unbox a) => Int -> (Int -> m a) -> m (MVector (PrimState m) a) Source #

*O(n)* Create a mutable vector of the given length (0 if the length is
negative) and fill it with the results of applying the monadic function to each
index. Iteration starts at index 0.

*Since: 0.12.3.0*

clone :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> m (MVector (PrimState m) a) Source #

Create a copy of a mutable vector.

## Growing

grow :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> Int -> m (MVector (PrimState m) a) Source #

Grow an unboxed vector by the given number of elements. The number must be
non-negative. Same semantics as in `grow`

for generic vector.

#### Examples

`>>>`

`import qualified Data.Vector.Unboxed as VU`

`>>>`

`import qualified Data.Vector.Unboxed.Mutable as MVU`

`>>>`

`mv <- VU.thaw $ VU.fromList ([('a', 10), ('b', 20), ('c', 30)] :: [(Char, Int)])`

`>>>`

`mv' <- MVU.grow mv 2`

Extra memory at the end of the newly allocated vector is initialized to 0
bytes, which for `Unbox`

instance will usually correspond to some default
value for a particular type, eg. `0`

for `Int`

, `False`

for `Bool`

,
etc. However, if `unsafeGrow`

was used instead this would not have been
guaranteed and some garbage would be there instead:

`>>>`

[('a',10),('b',20),('c',30),('\NUL',0),('\NUL',0)]`VU.freeze mv'`

Having the extra space we can write new values in there:

`>>>`

`MVU.write mv' 3 ('d', 999)`

`>>>`

[('a',10),('b',20),('c',30),('d',999),('\NUL',0)]`VU.freeze mv'`

It is important to note that the source mutable vector is not affected when the newly allocated one is mutated.

`>>>`

`MVU.write mv' 2 ('X', 888)`

`>>>`

[('a',10),('b',20),('X',888),('d',999),('\NUL',0)]`VU.freeze mv'`

`>>>`

[('a',10),('b',20),('c',30)]`VU.freeze mv`

*Since: 0.5*

unsafeGrow :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> Int -> m (MVector (PrimState m) a) Source #

Grow a vector by the given number of elements. The number must be non-negative but
this is not checked. Same semantics as in `unsafeGrow`

for generic vector.

*Since: 0.5*

## Restricting memory usage

clear :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> m () Source #

Reset all elements of the vector to some undefined value, clearing all references to external objects. This is usually a noop for unboxed vectors.

# Zipping and unzipping

zip :: (Unbox a, Unbox b) => MVector s a -> MVector s b -> MVector s (a, b) Source #

*O(1)* Zip 2 vectors

zip3 :: (Unbox a, Unbox b, Unbox c) => MVector s a -> MVector s b -> MVector s c -> MVector s (a, b, c) Source #

*O(1)* Zip 3 vectors

zip4 :: (Unbox a, Unbox b, Unbox c, Unbox d) => MVector s a -> MVector s b -> MVector s c -> MVector s d -> MVector s (a, b, c, d) Source #

*O(1)* Zip 4 vectors

zip5 :: (Unbox a, Unbox b, Unbox c, Unbox d, Unbox e) => MVector s a -> MVector s b -> MVector s c -> MVector s d -> MVector s e -> MVector s (a, b, c, d, e) Source #

*O(1)* Zip 5 vectors

zip6 :: (Unbox a, Unbox b, Unbox c, Unbox d, Unbox e, Unbox f) => MVector s a -> MVector s b -> MVector s c -> MVector s d -> MVector s e -> MVector s f -> MVector s (a, b, c, d, e, f) Source #

*O(1)* Zip 6 vectors

unzip :: (Unbox a, Unbox b) => MVector s (a, b) -> (MVector s a, MVector s b) Source #

*O(1)* Unzip 2 vectors

unzip3 :: (Unbox a, Unbox b, Unbox c) => MVector s (a, b, c) -> (MVector s a, MVector s b, MVector s c) Source #

*O(1)* Unzip 3 vectors

unzip4 :: (Unbox a, Unbox b, Unbox c, Unbox d) => MVector s (a, b, c, d) -> (MVector s a, MVector s b, MVector s c, MVector s d) Source #

*O(1)* Unzip 4 vectors

unzip5 :: (Unbox a, Unbox b, Unbox c, Unbox d, Unbox e) => MVector s (a, b, c, d, e) -> (MVector s a, MVector s b, MVector s c, MVector s d, MVector s e) Source #

*O(1)* Unzip 5 vectors

unzip6 :: (Unbox a, Unbox b, Unbox c, Unbox d, Unbox e, Unbox f) => MVector s (a, b, c, d, e, f) -> (MVector s a, MVector s b, MVector s c, MVector s d, MVector s e, MVector s f) Source #

*O(1)* Unzip 6 vectors

# Accessing individual elements

read :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> Int -> m a Source #

Yield the element at the given position.

write :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> Int -> a -> m () Source #

Replace the element at the given position.

modify :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> (a -> a) -> Int -> m () Source #

Modify the element at the given position.

modifyM :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> (a -> m a) -> Int -> m () Source #

Modify the element at the given position using a monadic function.

*Since: 0.12.3.0*

swap :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> Int -> Int -> m () Source #

Swap the elements at the given positions.

exchange :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> Int -> a -> m a Source #

Replace the element at the given position and return the old element.

unsafeRead :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> Int -> m a Source #

Yield the element at the given position. No bounds checks are performed.

unsafeWrite :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> Int -> a -> m () Source #

Replace the element at the given position. No bounds checks are performed.

unsafeModify :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> (a -> a) -> Int -> m () Source #

Modify the element at the given position. No bounds checks are performed.

unsafeModifyM :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> (a -> m a) -> Int -> m () Source #

Modify the element at the given position using a monadic function. No bounds checks are performed.

*Since: 0.12.3.0*

unsafeSwap :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> Int -> Int -> m () Source #

Swap the elements at the given positions. No bounds checks are performed.

unsafeExchange :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> Int -> a -> m a Source #

Replace the element at the given position and return the old element. No bounds checks are performed.

# Folds

mapM_ :: (PrimMonad m, Unbox a) => (a -> m b) -> MVector (PrimState m) a -> m () Source #

*O(n)* Apply the monadic action to every element of the vector, discarding the results.

*Since: 0.12.3.0*

imapM_ :: (PrimMonad m, Unbox a) => (Int -> a -> m b) -> MVector (PrimState m) a -> m () Source #

*O(n)* Apply the monadic action to every element of the vector and its index,
discarding the results.

*Since: 0.12.3.0*

forM_ :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> (a -> m b) -> m () Source #

*O(n)* Apply the monadic action to every element of the vector,
discarding the results. It's same as the `flip mapM_`

.

*Since: 0.12.3.0*

iforM_ :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> (Int -> a -> m b) -> m () Source #

*O(n)* Apply the monadic action to every element of the vector
and its index, discarding the results. It's same as the `flip imapM_`

.

*Since: 0.12.3.0*

foldl :: (PrimMonad m, Unbox a) => (b -> a -> b) -> b -> MVector (PrimState m) a -> m b Source #

*O(n)* Pure left fold.

*Since: 0.12.3.0*

foldl' :: (PrimMonad m, Unbox a) => (b -> a -> b) -> b -> MVector (PrimState m) a -> m b Source #

*O(n)* Pure left fold with strict accumulator.

*Since: 0.12.3.0*

foldM :: (PrimMonad m, Unbox a) => (b -> a -> m b) -> b -> MVector (PrimState m) a -> m b Source #

*O(n)* Monadic fold.

*Since: 0.12.3.0*

foldM' :: (PrimMonad m, Unbox a) => (b -> a -> m b) -> b -> MVector (PrimState m) a -> m b Source #

*O(n)* Monadic fold with strict accumulator.

*Since: 0.12.3.0*

foldr :: (PrimMonad m, Unbox a) => (a -> b -> b) -> b -> MVector (PrimState m) a -> m b Source #

*O(n)* Pure right fold.

*Since: 0.12.3.0*

foldr' :: (PrimMonad m, Unbox a) => (a -> b -> b) -> b -> MVector (PrimState m) a -> m b Source #

*O(n)* Pure right fold with strict accumulator.

*Since: 0.12.3.0*

foldrM :: (PrimMonad m, Unbox a) => (a -> b -> m b) -> b -> MVector (PrimState m) a -> m b Source #

*O(n)* Monadic right fold.

*Since: 0.12.3.0*

foldrM' :: (PrimMonad m, Unbox a) => (a -> b -> m b) -> b -> MVector (PrimState m) a -> m b Source #

*O(n)* Monadic right fold with strict accumulator.

*Since: 0.12.3.0*

ifoldl :: (PrimMonad m, Unbox a) => (b -> Int -> a -> b) -> b -> MVector (PrimState m) a -> m b Source #

*O(n)* Pure left fold (function applied to each element and its index).

*Since: 0.12.3.0*

ifoldl' :: (PrimMonad m, Unbox a) => (b -> Int -> a -> b) -> b -> MVector (PrimState m) a -> m b Source #

*O(n)* Pure left fold with strict accumulator (function applied to each element and its index).

*Since: 0.12.3.0*

ifoldM :: (PrimMonad m, Unbox a) => (b -> Int -> a -> m b) -> b -> MVector (PrimState m) a -> m b Source #

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

*Since: 0.12.3.0*

ifoldM' :: (PrimMonad m, Unbox a) => (b -> Int -> a -> m b) -> b -> MVector (PrimState m) a -> m b Source #

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

*Since: 0.12.3.0*

ifoldr :: (PrimMonad m, Unbox a) => (Int -> a -> b -> b) -> b -> MVector (PrimState m) a -> m b Source #

*O(n)* Pure right fold (function applied to each element and its index).

*Since: 0.12.3.0*

ifoldr' :: (PrimMonad m, Unbox a) => (Int -> a -> b -> b) -> b -> MVector (PrimState m) a -> m b Source #

*O(n)* Pure right fold with strict accumulator (function applied
to each element and its index).

*Since: 0.12.3.0*

ifoldrM :: (PrimMonad m, Unbox a) => (Int -> a -> b -> m b) -> b -> MVector (PrimState m) a -> m b Source #

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

*Since: 0.12.3.0*

ifoldrM' :: (PrimMonad m, Unbox a) => (Int -> a -> b -> m b) -> b -> MVector (PrimState m) a -> m b Source #

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

*Since: 0.12.3.0*

# Modifying vectors

nextPermutation :: (PrimMonad m, Ord e, Unbox e) => MVector (PrimState m) e -> m Bool Source #

Compute the next (lexicographically) permutation of given vector in-place. Returns False when input is the last permutation

## Filling and copying

set :: (PrimMonad m, Unbox a) => MVector (PrimState m) a -> a -> m () Source #

Set all elements of the vector to the given value.

Copy a vector. The two vectors must have the same length and may not overlap.

Move the contents of a vector. The two vectors must have the same length.

If the vectors do not overlap, then this is equivalent to `copy`

.
Otherwise, the copying is performed as if the source vector were
copied to a temporary vector and then the temporary vector was copied
to the target vector.

Copy a vector. The two vectors must have the same length and may not overlap. This is not checked.

Move the contents of a vector. The two vectors must have the same length, but this is not checked.

If the vectors do not overlap, then this is equivalent to `unsafeCopy`

.
Otherwise, the copying is performed as if the source vector were
copied to a temporary vector and then the temporary vector was copied
to the target vector.