The Standard ML Basis Library

The `VectorSlice` structure

Synopsis

signature VECTOR_SLICE structure VectorSlice :> VECTOR_SLICE

The VectorSlice structure provides an abstraction of subvectors for polymorphic vectors. A slice value can be viewed as a triple (v, i, n), where v is the underlying vector, i is the starting index, and n is the length of the subvector, with the constraint that 0 <= i <= i + n <= |v|, where |v| is the length of v. Slices provide a convenient notation for specifying and operating on a contiguous subset of elements in a vector.

Interface

type 'a slice val length : 'a slice -> int val sub : 'a slice * int -> 'a val full : 'a Vector.vector -> 'a slice val slice : 'a Vector.vector * int * int option -> 'a slice val subslice : 'a slice * int * int option -> 'a slice val base : 'a slice -> 'a Vector.vector * int * int val vector : 'a slice -> 'a Vector.vector val concat : 'a slice list -> 'a Vector.vector val isEmpty : 'a slice -> bool val getItem : 'a slice -> ('a * 'a slice) option val appi : (int * 'a -> unit) -> 'a slice -> unit val app : ('a -> unit) -> 'a slice -> unit val mapi : (int * 'a -> 'b) -> 'a slice -> 'b Vector.vector val map : ('a -> 'b) -> 'a slice -> 'b Vector.vector val foldli : (int * 'a * 'b -> 'b) -> 'b -> 'a slice -> 'b val foldri : (int * 'a * 'b -> 'b) -> 'b -> 'a slice -> 'b val foldl : ('a * 'b -> 'b) -> 'b -> 'a slice -> 'b val foldr : ('a * 'b -> 'b) -> 'b -> 'a slice -> 'b val findi : (int * 'a -> bool) -> 'a slice -> (int * 'a) option val find : ('a -> bool) -> 'a slice -> 'a option val exists : ('a -> bool) -> 'a slice -> bool val all : ('a -> bool) -> 'a slice -> bool val collate : ('a * 'a -> order) -> 'a slice * 'a slice -> order

Description

length sl

returns |sl|, the length (i.e., number of elements) of the slice.

sub (sl, i)

returns the i^(th) element of the slice sl. If i < 0 or |sl| <= i, then the Subscript exception is raised.

full vec

creates a slice representing the entire vector vec. It is equivalent to

slice(vec, 0, NONE)

slice (vec, i, sz)

creates a slice based on the vector vec starting at index i of the vector vec. If sz is NONE, the slice includes all of the elements to the end of the vector, i.e., vec[i..|vec|-1]. This raises Subscript if i < 0 or |vec| < i. If sz is SOME(j), the slice has length j, that is, it corresponds to vec[i..i+j-1]. It raises Subscript if i < 0 or j < 0 or |arr| < i + j. Note that, if defined, slice returns an empty slice when i = |vec|.

subslice (sl, i, sz)

creates a slice based on the given slice sl starting at index i of sl. If sz is NONE, the slice includes all of the elements to the end of the slice, i.e., sl[i..|sl|-1]. This raises Subscript if i < 0 or |sl| < i. If sz is SOME(j), the slice has length j, that is, it corresponds to sl[i..i+j-1]. It raises Subscript if i < 0 or j < 0 or |sl| < i + j. Note that, if defined, slice returns an empty slice when i = |sl|.

base sl

returns a triple (vec, i, n) representing the concrete representation of the slice. vec is the underlying vector, i is the starting index, and n is the length of the slice.

vector sl

generates a vector from the slice sl. Specifically, the result is equivalent to

          Vector.tabulate (length sl, fn i => sub (sl, i))

concat l

is the concatenation of all the slices in l. This raises Size if the sum of all the lengths is greater than Vector.maxLen.

isEmpty sl

returns true if sl has length 0.

getItem sl

returns the first item in sl and the rest of the slice, or NONE if sl is empty.

appi f sl

app f sl

These apply the function f to the elements of a slice in left to right order (i.e., increasing indices). The more general appi function supplies f with the index of the corresponding element in the slice. The expression app f sl is equivalent to appi (f o #2) sl.

mapi f sl

map f sl

These functions generate new vectors by mapping the function f from left to right over the argument slice. The more general mapi function supplies both the element and the element's index in the slice to the function f. The first expression is equivalent to:

let
  fun ff (i,a,l) = f(i,a)::l
in
  Vector.fromList (rev (foldli ff [] sl))
end

The latter expression is equivalent to:

      mapi (f o #2) sl

foldli f init sl

foldri f init sl

foldl f init sl

foldr f init sl

These fold the function f over all the elements of a vector slice, using the value init as the initial value. The functions foldli and foldl apply the function f from left to right (increasing indices), while the functions foldri and foldr work from right to left (decreasing indices). The more general functions foldli and foldri supply f with the index of the corresponding element in the slice.

Refer to the MONO_ARRAY manual pages for reference implementations of the indexed versions.

The expression foldl f init sl is equivalent to:

foldli (fn (_, a, x) => f(a, x)) init sl

The analogous equivalence holds for foldri and foldr.

findi f sl

find f sl

These apply f to each element of the slice sl, from left to right (i.e., increasing indices), until a true value is returned. If this occurs, the functions return the element; otherwise, they return NONE. The more general version findi also supplies f with the index of the element in the slice and, upon finding an entry satisfying the predicate, returns that index with the element.

exists f sl

applies f to each element x of the slice sl, from left to right (i.e., increasing indices), until f(x) evaluates to true; it returns true if such an x exists and false otherwise.

all f sl

applies f to each element x of the slice sl, from left to right (i.e., increasing indices), until f(x) evaluates to false; it returns false if such an x exists and true otherwise. It is equivalent to

not(exists (not o f
) sl))

collate f (sl, sl2)

performs lexicographic comparison of the two slices using the given ordering f on elements.

The Standard ML Basis Library

The VectorSlice structure

Synopsis

Interface

Description

See Also

The `VectorSlice` structure