C++ 浮点数组初始化
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C++ float array initialization
提问by Adam Matan
Possible Duplicate:
C and C++ : Partial initialization of automatic structure
可能的重复：
C 和 C++：自动结构的部分初始化
While reading Code Complete, I came across an C++ array initialization example:
在阅读Code Complete 时，我遇到了一个 C++ 数组初始化示例：
float studentGrades[ MAX_STUDENTS ] = { 0.0 };
I did not know C++ could initialize the entire array, so I've tested it:
我不知道 C++ 可以初始化整个数组，所以我测试了它：
#include <iostream>
using namespace std;
int main() {
const int MAX_STUDENTS=4;
float studentGrades[ MAX_STUDENTS ] = { 0.0 };
for (int i=0; i<MAX_STUDENTS; i++) {
cout << i << " " << studentGrades[i] << '\n';
}
return 0;
}
The program gave the expected results:
该计划给出了预期的结果：
0 0
1 0
2 0
3 0
But changing the initialization value from 0.0to, say, 9.9:
但是将初始化值从 更改0.0为，例如9.9：
float studentGrades[ MAX_STUDENTS ] = { 9.9 };
Gave the interesting result:
给出了有趣的结果：
0 9.9
1 0
2 0
3 0
Does the initialization declaration set only the first element in the array?
初始化声明是否只设置数组中的第一个元素？
回答by Ed S.
If you use anything but empty braces then you only initialize the first N positions to that value and all others are initialized to 0. In this case, N is the number of arguments you passed to the initialization list, i.e.,
如果你使用除了空大括号之外的任何东西，那么你只将前 N 个位置初始化为该值，所有其他位置都初始化为 0。在这种情况下，N 是你传递给初始化列表的参数数量，即，
float arr1[10] = { }; // all elements are 0
float arr2[10] = { 0 }; // all elements are 0
float arr3[10] = { 1 }; // first element is 1, all others are 0
float arr4[10] = { 1, 2 }; // first element is 1, second is 2, all others are 0
回答by Marcelo Cantos
No, it sets all members/elements that haven't been explicitly set to their default-initialisation value, which is zero for numeric types.
不，它将所有尚未明确设置的成员/元素设置为其默认初始化值，对于数字类型为零。
