cstdio

cstdio streams vs iostream streams?

由 ぐ巨炮叔叔 提交于 2019-12-30 01:37:05
问题 I just learned of the existence of the ios_base::sync_with_stdio function, which basically allows you to turn off (or on if you already turned it off) the synchronization between iostream streams that are used in C++ and the cstdio streams that are part of Standard C. Now, I always thought that stdout , stderr and stdin in C were essentially wrapped in a set of objects in C++ in the iostreams classes. But if they have to be synchronized with each other, this would indicate that C++'s iostream

Difference between %u and %d in scanf()

由 流过昼夜 提交于 2019-12-25 17:08:54
问题 In C++, if I read an integer from a string, it seems it does not really matter whether I use u or d as conversion specifier as both accept even negative integers. #include <cstdio> using namespace std; int main() { int u, d; sscanf("-2", "%u", &u); sscanf("-2", "%d", &d); puts(u == d ? "u == d" : "u != d"); printf("u: %u %d\n", u, u); printf("d: %u %d\n", d, d); return 0; } Ideone.com I dug deeper to find if there is any difference. I found that int u, d; sscanf("-2", "%u", &u); sscanf("-2",

cstdio streams vs iostream streams?

由 一世执手 提交于 2019-11-30 06:12:13
I just learned of the existence of the ios_base::sync_with_stdio function, which basically allows you to turn off (or on if you already turned it off) the synchronization between iostream streams that are used in C++ and the cstdio streams that are part of Standard C. Now, I always thought that stdout , stderr and stdin in C were essentially wrapped in a set of objects in C++ in the iostreams classes. But if they have to be synchronized with each other, this would indicate that C++'s iostream classes are not a wrapper around C's stdin etc. I'm quite confused by this? Can someone clarify how C+

Skipping expected characters like scanf() with cin

由 坚强是说给别人听的谎言 提交于 2019-11-27 06:16:07
问题 How to achieve scanf("%d # %d",&a,&b); sort of effect with cin in C++ ? 回答1: You could create your own stream manipulator. It is fairly easy. #include <ios> #include <iostream> using namespace std; // skips the number of characters equal to the length of given text // does not check whether the skipped characters are the same as it struct skip { const char * text; skip(const char * text) : text(text) {} }; std::istream & operator >> (std::istream & stream, const skip & x) { ios_base::fmtflags
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