我写了myPercolation.ml
。为什么ocamlc说我不匹配{}而我没有?
open MyUnionFind
module type MyPercolationSig = sig
type percolation
val create_percolation : int -> percolation
val open_site : percolation -> int -> int -> unit
val is_open : percolation -> int -> int -> bool
val is_full : percolation -> int -> int -> bool
val can_percolates : percolation -> bool
end
module MyPercolation : MyPercolationSig = struct
exception IndexOutOfBounds;;
type percolation =
{n : int;
sites: bool array;
union : MyUnionFind.union_find};;
let create_percolation n =
{n = n; sites = Array.make (n*n) false; union = MyUnionFind.create_union (n*n)};;
let open_site p i j =
let {n;_;union} = p
in
if not (is_open p i j) then
begin
sites.(index_of n i j) <- true;
if i - 1 >= 1 && i - 1 <= n && is_open n (i-1) j then
MyUnionFind.union union (index_of n i j) (index_of n (i-1) j)
else if i + 1 >= 1 && i + 1 <= n && is_open n (i+1) j then
MyUnionFind.union union (index_of n i j) (index_of n (i+1) j)
else if j - 1 >= 1 && j - 1 <= n && is_open n i (j-1) then
MyUnionFind.union union (index_of n i j) (index_of n i (j-1))
else if j + 1 >= 1 && j + 1 <= n && is_open n i (j+1) then
MyUnionFind.union union (index_of n i j) (index_of n i (j+1))
end;;
let index_of n i j = n * (i - 1) + j;;
let is_open {n;sites;_} i j =
if i < 1 || i > n || j < 1 || j > n then
raise IndexOutOfBounds
else
sites.(index_of n i j);;
let is_full {n;_;union} i j =
let rec is_connected_top j' =
if j = 0 then false
else
if MyUnionFind.is_connected union (index_of n i j) (index_of n 0 j') then true
else is_connected_top (j'-1)
in is_connected_top n;;
let can_percolates p =
let {n;_;_} = p
in
let rec is_full_bottom j =
if j = 0 then false
else
if is_full p n j then true
else is_full_bottom (j-1)
end
请忽略包MyUnionFind
包。这只是union-find
算法的自制实现。
,当我试图编译myPercolation.ml
,我得到了这样的错误:
$ ocamlc -c myPercolation.ml
File "myPercolation.ml", line 25, characters 11-12:
Error: Syntax error: '}' expected
File "myPercolation.ml", line 25, characters 8-9:
Error: This '{' might be unmatched
我认为错误是在let open_site p i j
功能谈论let {n;_;union} = p
。
我已经通读了该行和所有代码多次,但我仍然没有看到该行中有任何不匹配的{}
。
任何人都可以帮忙吗?
'{n; union}'会给我一个编译器警告。如果你认为编译警告是不必要的,你可以使用'{n;联盟; _}'但是下划线必须是最后一个。 – rgrinberg 2013-02-19 00:58:51
我没有看到OCaml 4.00.0默认设置的任何警告。但是你是对的,如果它是最后一个字段,则允许'_'。 – 2013-02-19 01:07:48
我认为必须启用警告。请参阅:http://caml.inria.fr/pub/docs/manual-ocaml-4.00/manual021.html#toc78 – rgrinberg 2013-02-19 01:15:49