一个正常的数组初始化一个默认值 [英] Initialization of a normal array with one default value
问题描述
C ++注:阵列初始化过有一个很好的列表阵列的初始化。我有一个
C++ Notes: Array Initialization has a nice list over initialization of arrays. I have a
int array[100] = {-1};
希望它是充满-1的,但它不是,只有第一个值,其余为0的混合随机值。
expecting it to be full with -1's but its not, only first value is and the rest are 0's mixed with random values.
在code
int array[100] = {0};
工作得很好,并设置每个元素为0。
works just fine and sets each element to 0.
我缺少的是在这里..不能在一个初始化如果该值不为零?
What am I missing here.. Can't one initialize it if the value isn't zero ?
2:是默认的初始化(如上)不是通过整个阵列通常的循环更快,分配一个值还是它做同样的事情。
2: Is the default initialization (as above ) faster than the usual loop through the whole array and assign a value or does it do the same thing?
推荐答案
使用您所使用的语法:
int array[100] = {-1};
说的第一个元素设置为 1
剩下的 0
,因为所有的元素略设置到 0
。
says "set the first element to -1
and the rest to 0
" since all omitted elements are set to 0
.
在C ++中,将它们全部设置为 1
,您可以使用类似的 的std :: fill_n
(从<&算法GT;
):
In C++, to set them all to -1
, you can use something like std::fill_n
(from <algorithm>
):
std::fill_n(array, 100, -1);
在便携式C,你必须推出自己的循环。有编译器的扩展,也可以依靠实现定义的快捷方式,如果这是可以接受的。
In portable C, you have to roll your own loop. There are compiler-extensions or you can depend on implementation-defined behavior as a shortcut if that's acceptable.
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