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Convert from ASCII string encoded in Hex to plain ASCII?
...61756c", "hex") works for Python 2 and Python 3. But it returns a bytes() string in Python 3. But that's reasonable for an ASCII string.
– Mark Evans
Aug 7 '15 at 8:46
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How is std::function implemented?
...;
}
};
// examples
int main()
{
int i = 0;
auto fn = [i](std::string const& s) mutable
{
std::cout << ++i << ". " << s << std::endl;
};
fn("first"); // 1. first
fn("second"); ...
What is std::string::c_str() lifetime?
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The c_str() result becomes invalid if the std::string is destroyed or if a non-const member function of the string is called. So, usually you will want to make a copy of it if you need to keep it around.
In the case of your example, it appears that the results of c_str(...
How can I safely encode a string in Java to use as a filename?
I'm receiving a string from an external process. I want to use that String to make a filename, and then write to that file. Here's my code snippet to do this:
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VC/Linux C++ 递归访问目录下所有文件 - C/C++ - 清泛网 - 专注C/C++及内核技术
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#include <dirent.h>
#include <iostream>
#include <cstdlib>
#include <cstring>
using namespace std;
void GetFileInDir(string dirName)
{
DIR* Dir = NULL;
struct dirent* file = NULL;
if (dirName[dirName.size()-1] != '/')
{
dirName += "/";
}
if ((Dir = open...
Why historically do people use 255 not 256 for database field magnitudes?
...char data (unless constrained otherwise). Most systems treat such an empty string as distinct from NULL, but some systems (notably Oracle) treat an empty string identically to NULL. For systems where an empty string is not NULL, an additional bit somewhere in the row would be needed to indicate whet...
Count character occurrences in a string in C++
How can I count the number of "_" in a string like "bla_bla_blabla_bla" ?
13 Answers
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How can we match a^n b^n with Java regex?
...'s start with a simpler problem: we want to match a+ at the beginning of a string, but only if it's followed immediately by b+. We can use ^ to anchor our match, and since we only want to match the a+ without the b+, we can use lookahead assertion (?=…).
Here is our pattern with a simple test harn...
Best way to parseDouble with comma as decimal separator?
..." it will happily return 1.23 without indicating to you that the passed-in String contained non-parsable characters. In some situations that might actually be desirable, but I don't think it's usually the desired behavior.
– E-Riz
Jan 17 '13 at 19:37
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C++ new int[0] — will it allocate memory?
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I guarantee you that new int[0] costs you extra space since I have tested it.
For example,
the memory usage of
int **arr = new int*[1000000000];
is significantly smaller than
int **arr = new int*[1000000000];
for(int i =0; i < 1000000000; i++) {
arr[i]...