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09-list-initialization-3.cpp
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76 lines (61 loc) · 1.82 KB
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// d2mcpp: https://github.com/mcpp-community/d2mcpp
// license: Apache-2.0
// reference solution for: dslings/cpp11/09-list-initialization-3.cpp
//
// 用途: 仅给 CI 与维护者参考使用,不是教程入口。
// 教程练习入口: dslings/cpp11/09-list-initialization-3.cpp
//
// 教学要点:
// 1. 用户提供构造函数的类型不再是聚合, Point 需要显式定义 (int, int) 构造函数
// 才能用 `{1, 2}` 这种形式构造。
// 2. 列表初始化优先选 std::initializer_list 重载, 这里去掉 initializer_list 重载,
// 让 `MyVector vec4 { 1, 10 }` 命中 (int, int) 构造函数。
#include <d2x/cpp/common.hpp>
#include <iostream>
#include <vector>
class MyVector {
int mSize;
int *data;
public:
MyVector(int val) {
mSize = 1;
data = new int[mSize];
data[0] = val;
}
MyVector(int v1, int sz) {
mSize = sz;
data = new int[mSize];
for (int i = 0; i < sz; ++i) {
data[i] = v1;
}
}
// 注意: 移除 initializer_list 构造函数, 否则 `MyVector{1, 10}` 会优先匹配
// initializer_list, 导致 size() 等于 2 而非 10.
MyVector(const MyVector& other) = delete;
MyVector(MyVector&& other) = delete;
~MyVector() {
delete[] data;
}
int size() const {
return mSize;
}
};
struct Point {
int x, y;
Point() : x {0}, y{0} { }
Point(int x_, int y_) : x{x_}, y{y_} { } // 添加 (int, int) 构造函数
};
int main() {
Point p1 = {1, 2};
Point p2 {3, 4};
(void)p1; (void)p2;
MyVector vec1(1);
d2x_assert_eq(vec1.size(), 1);
MyVector vec2 { 1 };
d2x_assert_eq(vec2.size(), 1);
MyVector vec3(1, 10);
d2x_assert_eq(vec3.size(), 10);
MyVector vec4 { 1, 10 };
d2x_assert_eq(vec4.size(), 10);
return 0;
}