原文
bool isRectangular(A)(A a) if (isArray!A)
{
size_t[] dummy;
return isRectangular(a, dummy);
}
bool isRectangular(A)(A a, out size_t[] shape) if (isArray!A)
{
size_t first_length = a[0].length;
foreach (e; a)
{
if (e.length != first_length) return false;
}
shape = [a.length, first_length];
return true;
}
unittest
{
size_t[] shape;
assert(isRectangular([[1, 2], [3, 4], [5, 6]], shape));
assert(shape == [3, 2]);
assert(!isRectangular([[1, 2], [], [3, 4]]));
}
//一维数组
bool isRectangular(A)(A a, out size_t[] shape) if (isArray!A)
{
shape = [a.length];
alias E = typeof(a[0]);
static if (isArray!E)
{
size_t first_length = a[0].length;
shape ~= first_length;
foreach (e; a)
{
if (e.length != first_length) return false;
}
}
return true;
}
unittest /* one dimension */
{
size_t[] shape;
assert(isRectangular([1, 2, 3], shape));
assert(shape == [3]);
}
//递归,
bool isRectangular(A)(A a, out size_t[] shape) if (isArray!A)
{
shape = [a.length];
alias E = typeof(a[0]);
static if (isArray!E)
{
size_t[] first_shape;
if (!isRectangular(a[0], first_shape)) return false;
shape ~= first_shape;
foreach (e; a)
{
size_t[] e_shape;
if (!isRectangular(e, e_shape)) return false;
if (e_shape != first_shape) return false;
}
}
return true;
}
unittest /* higher dimensions */
{
size_t[] shape;
assert(isRectangular([
[[ 1, 2, 3, 4], [ 5, 6, 7, 8], [ 9, 10, 11, 12]],
[[13, 14, 15, 16], [17, 18, 19, 20], [21, 22, 23, 24]]
], shape));
assert(shape == [2, 3, 4]);
}
//还可改进,但不管了.
import std.range.primitives:;
template FlatElementType(A) if (isArray!A)
{
alias E = ElementType!A;
static if (isArray!E)
{
alias FlatElementType = FlatElementType!E;
}
else
{
alias FlatElementType = E;
}
}
unittest
{
static assert(is(FlatElementType!(int[]) == int));
static assert(is(FlatElementType!(int[][]) == int));
static assert(is(FlatElementType!(int[][][]) == int));
}
auto flatten(A)(A a) if (isArray!A)
{
FlatElementType!A[] result;
foreach (i; a)
{
static if (isArray!(typeof(i)))
result ~= flatten(i);
else
result ~= i;
}
return result;
}
unittest
{
assert(flatten([[1, 2], [3, 4, 5], [6]]) ==
[1, 2, 3, 4, 5, 6]);
assert(flatten([[[1, 2], [3, 4]], [[5, 6], [7, 8]]]) ==
[1, 2, 3, 4, 5, 6, 7, 8]);
}