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// https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/p2630r0.html
// C99:
#include <stdio.h>
#include <stc/cspan.h>
using_cspan3(span, double); // define span, span2, span3
// Set all elements of a rank-2 mdspan to zero.
void zero_2d(span2 grid2d) {
c_static_assert(cspan_rank(&grid2d) == 2);
for (int i = 0; i < grid2d.shape[0]; ++i) {
for (int j = 0; j < grid2d.shape[1]; ++j) {
*cspan_at(&grid2d, i,j) = 0;
}
}
}
void zero_surface(span3 grid3d) {
c_static_assert(cspan_rank(&grid3d) == 3);
zero_2d(cspan_slice(span2, &grid3d, {0}, {c_ALL}, {c_ALL}));
zero_2d(cspan_slice(span2, &grid3d, {c_ALL}, {0}, {c_ALL}));
zero_2d(cspan_slice(span2, &grid3d, {c_ALL}, {c_ALL}, {0}));
zero_2d(cspan_slice(span2, &grid3d, {grid3d.shape[0]-1}, {c_ALL}, {c_ALL}));
zero_2d(cspan_slice(span2, &grid3d, {c_ALL}, {grid3d.shape[1]-1}, {c_ALL}));
zero_2d(cspan_slice(span2, &grid3d, {c_ALL}, {c_ALL}, {grid3d.shape[2]-1}));
}
int main() {
double arr[3*4*5];
for (int i=0; i<c_arraylen(arr); ++i) arr[i] = i + 1.0;
span3 md = cspan_md(arr, 3, 4, 5);
zero_surface(md);
for (int i = 0; i < md.shape[0]; i++) {
for (int j = 0; j < md.shape[1]; j++) {
for (int k = 0; k < md.shape[2]; k++)
printf(" %2g", *cspan_at(&md, i,j,k));
puts("");
}
puts("");
}
}
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