回答編集履歴
4
修正
answer
CHANGED
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@@ -20,6 +20,7 @@
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20
20
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21
21
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template<typename T, size_t Dim, typename... Args>
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22
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NPtr<T, Dim>::type AllocDim(Args... _width){
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23
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+
static_assert(Dim == sizeof...(_width), "sizeof...(_width) must equal Dim");
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std::array<size_t, Dim> width = {_width...};
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size_t elements = 1, points = 0;
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25
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for(size_t i = 0; i < Dim; i++) {
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3
修正
answer
CHANGED
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@@ -2,10 +2,12 @@
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2
2
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ご質問のように仮引数によって動的に型を決定する事はできません。
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3
3
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4
4
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---
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5
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-
C++においてはテンプレートによって作れ
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5
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+
C++においてはテンプレートによって作れました。
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6
6
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が、前述のようにコンパイル時に`Dim`が決定されている必要があったりと実用的かは微妙です
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7
7
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8
8
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```c++
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9
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+
#include <array>
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10
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+
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9
11
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template <typename T, size_t Dim>
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10
12
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struct NPtr{
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11
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typedef NPtr<T,Dim-1>::type* type;
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@@ -16,8 +18,9 @@
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16
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typedef T type;
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};
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18
20
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19
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-
template<typename T, size_t Dim>
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21
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+
template<typename T, size_t Dim, typename... Args>
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20
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-
NPtr<T, Dim>::type AllocDim(
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22
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+
NPtr<T, Dim>::type AllocDim(Args... _width){
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23
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+
std::array<size_t, Dim> width = {_width...};
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21
24
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size_t elements = 1, points = 0;
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22
25
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for(size_t i = 0; i < Dim; i++) {
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23
26
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points += elements;
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@@ -41,10 +44,14 @@
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41
44
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*it++ = (void*)(base + memo + l * diff);
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42
45
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}
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43
46
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}
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47
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+
size_t last = width[Dim-1];
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44
48
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for(size_t i = 0; it < (void**)data; i++) {
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45
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-
*it++ = (void*)(data + i * sizeof(T));
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49
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+
*it++ = (void*)(data + last * i * sizeof(T));
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46
50
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}
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47
51
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return (typename NPtr<T, Dim>::type) result;
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48
52
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}
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49
53
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54
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+
int main(){
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55
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char*** ptr = AllocDim<char, 3>(3,2,2);
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56
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}
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50
57
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```
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2
修正
answer
CHANGED
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@@ -6,7 +6,6 @@
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6
6
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が、前述のようにコンパイル時に`Dim`が決定されている必要があったりと実用的かは微妙です
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7
7
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8
8
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```c++
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9
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-
// 作りかけ
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10
9
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template <typename T, size_t Dim>
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11
10
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struct NPtr{
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12
11
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typedef NPtr<T,Dim-1>::type* type;
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@@ -25,18 +24,27 @@
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25
24
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elements *= width[i];
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26
25
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}
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27
26
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points -= 1;
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28
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-
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29
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-
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27
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+
size_t size = elements * sizeof(T) + points * sizeof(void**);
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28
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+
void* result = malloc(size);
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30
29
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if(!result)
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31
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-
return
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30
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+
return nullptr;
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32
31
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void** it = (void**)result;
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33
32
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char* data = (char*)(it+points);
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33
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+
size_t memo = 0;
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34
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+
size_t t = 1;
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34
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-
for(size_t i = 0; i < Dim-
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35
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+
for(size_t i = 0; i < Dim-2; i++) {
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36
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+
size_t w = width[i], diff = width[i+1];
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37
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+
memo += w;
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38
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+
t *= w;
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35
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-
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39
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+
void** base = it;
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40
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+
for(size_t l = 0; l < t; l++) {
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41
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+
*it++ = (void*)(base + memo + l * diff);
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42
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+
}
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36
43
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}
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37
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-
for(size_t i = 0;
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44
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+
for(size_t i = 0; it < (void**)data; i++) {
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38
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-
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45
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+
*it++ = (void*)(data + i * sizeof(T));
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39
46
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}
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40
47
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return (typename NPtr<T, Dim>::type) result;
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41
48
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}
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49
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+
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42
50
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```
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1
修正
answer
CHANGED
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@@ -37,6 +37,6 @@
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37
37
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for(size_t i = 0; i < width[Dim-1]; i++) {
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38
38
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// ここ
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39
39
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}
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40
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-
return (NPtr<T, Dim>::type) result;
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40
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+
return (typename NPtr<T, Dim>::type) result;
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41
41
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}
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42
42
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```
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