
Structure List
(* List  SML Basis Library *)
datatype list = datatype list
exception Empty
val null : 'a list > bool
val hd : 'a list > 'a (* Empty *)
val tl : 'a list > 'a list (* Empty *)
val last : 'a list > 'a (* Empty *)
val nth : 'a list * int > 'a (* Subscript *)
val take : 'a list * int > 'a list (* Subscript *)
val drop : 'a list * int > 'a list (* Subscript *)
val length : 'a list > int
val rev : 'a list > 'a list
val @ : 'a list * 'a list > 'a list
val concat : 'a list list > 'a list
val revAppend : 'a list * 'a list > 'a list
val app : ('a > unit) > 'a list > unit
val map : ('a > 'b) > 'a list > 'b list
val mapPartial : ('a > 'b option) > 'a list > 'b list
val find : ('a > bool) > 'a list > 'a option
val filter : ('a > bool) > 'a list > 'a list
val partition : ('a > bool ) > 'a list > ('a list * 'a list)
val foldr : ('a * 'b > 'b) > 'b > 'a list > 'b
val foldl : ('a * 'b > 'b) > 'b > 'a list > 'b
val exists : ('a > bool) > 'a list > bool
val all : ('a > bool) > 'a list > bool
val tabulate : int * (int > 'a) > 'a list (* Size *)
val getItem : 'a list > ('a * 'a list) option
(*
['a list] is the type of lists of elements of type 'a.
[null xs] is true iff xs is nil.
[hd xs] returns the first element of xs. Raises Empty if xs is nil.
[tl xs] returns all but the first element of xs.
Raises Empty if xs is nil.
[last xs] returns the last element of xs. Raises Empty if xs is nil.
[nth(xs, i)] returns the i'th element of xs, counting from 0.
Raises Subscript if i<0 or i>=length xs.
[take(xs, i)] returns the first i elements of xs. Raises Subscript
if i<0 or i>length xs.
[drop(xs, i)] returns what is left after dropping the first i
elements of xs. Raises Subscript if i<0 or i>length xs.
It holds that take(xs, i) @ drop(xs, i) = xs when 0 <= i <= length xs.
[length xs] returns the number of elements in xs.
[rev xs] returns the list of xs's elements, reversed.
[xs @ ys] returns the list which is the concatenation of xs and ys.
[concat xss] returns the list which is the concatenation of all the
lists in xss.
[revAppend(xs, ys)] is equivalent to rev xs @ ys, but more efficient.
[app f xs] applies f to the elements of xs, from left to right.
[map f xs] applies f to each element x of xs, from left to
right, and returns the list of f's results.
[mapPartial f xs] applies f to each element x of xs, from left
to right, and returns the list of those y's for which f(x)
evaluated to SOME y.
[find p xs] applies f to each element x of xs, from left to
right until p(x) evaluates to true; returns SOME x if such an x
exists otherwise NONE.
[filter p xs] applies p to each element x of xs, from left to
right, and returns the sublist of those x for which p(x) evaluated
to true.
[partition p xs] applies p to each element x of xs, from left
to right, and returns a pair (pos, neg) where pos is the sublist
of those x for which p(x) evaluated to true, and neg is the sublist of
those for which p(x) evaluated to false.
[foldr op% e xs] evaluates x1 % (x2 % ( ... % (x(n1) % (xn % e)) ... ))
where xs = [x1, x2, ..., x(n1), xn], and % is taken to be infixed.
[foldl op% e xs] evaluates xn % (x(n1) % ( ... % (x2 % (x1 % e))))
where xs = [x1, x2, ..., x(n1), xn], and % is taken to be infixed.
[exists p xs] applies p to each element x of xs, from left to
right until p(x) evaluates to true; returns true if such an x
exists, otherwise false.
[all p xs] applies p to each element x of xs, from left to
right until p(x) evaluates to false; returns false if such an x
exists, otherwise true.
[tabulate(n, f)] returns a list of length n whose elements are
f(0), f(1), ..., f(n1), created from left to right. Raises Size
if n<0.
[getItem xs] attempts to extract an element from the list xs. It
returns NONE if xs is empty, and returns SOME (x, xr) if xs=x::xr.
This can be used for scanning booleans, integers, reals, and so on
from a list of characters. For instance, to scan a decimal integer
from a list cs of characters, compute
Int.scan StringCvt.DEC List.getItem cs
*)
