静态标注数组的规则 [英] Rules for statically dimensioning arrays
问题描述
回到旧C的时代，只有数字文字可用作静态分配数组的尺寸 - 尺寸必须是
解析为常数/编译前。现在我开始怀疑（！）这不再是C或C ++的情况:(
任何人都可以升级我目前的状态/版本的规则？（对于
C ++）
确切地说，我回溯了多少年了？
Samee
在c ++中你可以使用stl容器 - 当使用push_back时不需要
预先分配内存，请参阅
http://www.sgi.com/tech/stl/Vector.html
- #include< iostream>
- #include< vector>
-
-使用命名空间std;
-
-int main（void）
- {
- vector< int> v;
-
- cout<< v.capacity（）<< endl;
- cout<< v.size（）<< endl;
-
- v.push_back（1）;
-
- cout<< v.capacity（）<< endl;
- cout<< v.size（）<<结束;
-
- v.reserve（25）;
- cout<< v.capacity（）<< endl;
- cout<< v.size（）<< endl;
-
- 返回0;
- }
< blockquote> Samee Zahur写道：
在旧C的时代，只有数字文字可用作静态分配数组的尺寸 - 尺寸必须为
在编译时/之前解析为常量。现在我开始怀疑（！）用C或C ++不再是这种情况:(
对于C，它不再是真的。
任何人都可以使用当前状态/版本的规则升级我吗？（对于
C ++）
仍然相同。静态分配的大小数组必须是编译时间
常量。
确切地说，我回溯了多少年???
我不知道。
" Samee Zahur"< sa ********* @ gmail。 com>在消息中写道
news：11 ********************** @ o13g2000cwo.googlegr oups.com ...在旧C的时代，只有数字文字可用作静态分配数组的维度 - 大小必须在编译时/之前解析为常量。现在我开始怀疑（！）用C或C ++不再是这种情况:(
任何人都可以用规则的现状/版本打我？ （对于
C ++）
这对于C ++来说还没有改变（因为C ++是从ANSI C''90
标准派生的）。但是C ++提供标准库容器作为首选
意味着存储动态大小的集合。
确切地说，我回溯了多少年???
1999年，ANSI / ISO C标准的更新引入了运行时大小的数组
。例如：
void f（int n）
{
char storage [n] = {0}; //在运行时定义的大小
}
C ++的等价物是：
std :: vector< char>存储（i）;
它有几个好处，能够调整集合的大小，以及在
$的情况下明确定义的行为b $ b内存不足错误 - 以及其他专业人员。
这就是说，为了保持与C的紧密兼容性，下一个C ++标准可能是b
包含C语言的这个新的
功能。
问候，
Ivan
-
http://ivan.vecerina.com/contact/?subject=NG_POST < - 电子邮件联系表格
Back in the days of old C, only numeric literals could be used as
dimensions for statically allocated arrays - the size had to be
resolved to a constant at/before compile time. Now I''m beginning to
suspect(!) that this is no longer the case either with C or with C++ :(
Can anyone upgrade me with the present state/version of rules? (for
C++)
Exactly, by how many years am I back-dated ???
Samee
in c++ you can use stl containers - when use push_back there''s no need
to allocate memory beforehand, see as well e.g.
http://www.sgi.com/tech/stl/Vector.html
-#include <iostream>
-#include <vector>
-
-using namespace std;
-
-int main(void)
-{
- vector<int> v;
-
- cout << v.capacity() << endl;
- cout << v.size() << endl;
-
- v.push_back(1);
-
- cout << v.capacity() << endl;
- cout << v.size() << endl;
-
- v.reserve(25);
- cout << v.capacity() << endl;
- cout << v.size() << endl;
-
- return 0;
-}
Samee Zahur wrote:
Back in the days of old C, only numeric literals could be used as
dimensions for statically allocated arrays - the size had to be
resolved to a constant at/before compile time. Now I''m beginning to
suspect(!) that this is no longer the case either with C or with C++ :(
For C, it is no longer true.
Can anyone upgrade me with the present state/version of rules? (for
C++)
Still the same. sizes of statically allocated arrays must be compile-time
constants.
Exactly, by how many years am I back-dated ???
I don''t know.
"Samee Zahur" <sa*********@gmail.com> wrote in message
news:11**********************@o13g2000cwo.googlegr oups.com...Back in the days of old C, only numeric literals could be used as
dimensions for statically allocated arrays - the size had to be
resolved to a constant at/before compile time. Now I''m beginning to
suspect(!) that this is no longer the case either with C or with C++ :(
Can anyone upgrade me with the present state/version of rules? (for
C++) This has not changed for C++ yet (as C++ is derived from the ANSI C ''90
standard). But C++ offers standard library containers as a preferred
means to store dynamically sized collections.
Exactly, by how many years am I back-dated ???
In 1999, an update to the ANSI/ISO C standard has introduced
run-time sized arrays. E.g.:
void f(int n)
{
char storage[n] = {0}; // size defined at run time
}
The C++ equivalent is:
std::vector<char> storage(i);
It has several benefits, in terms of being able to resize
the collection, and well-defined behavior in case of an
out-of-memory error -- among other pros.
This said, to maintain close compatibility with C, it is
likely that the next C++ standard will incorporate this new
feature of the C language.
Regards,
Ivan
--
http://ivan.vecerina.com/contact/?subject=NG_POST <- email contact form
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