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Combine two or more columns in a dataframe into a new column with a new name
...f$s)
df
# n s b x
# 1 2 aa TRUE 2 aa
# 2 3 bb FALSE 3 bb
# 3 5 cc TRUE 5 cc
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Linux反编译全攻略 - 操作系统(内核) - 清泛网 - 专注C/C++及内核技术
...在目录。运行“ objdump -x cm2 ”，显示如下：
代码:
[ncc2008@localhost]$ objdump -x cm2
cm2: file format elf32-i386
cm2
architecture: i386, flags 0x00000102:
EXEC_P, D_PAGED
start address 0x08048080
程序头：
LOAD off 0x00000000 vaddr 0x08048000 paddr 0x...
Resolve build errors due to circular dependency amongst classes
... A.h
class A {
B _b;
};
// file: B.h
class B {
A _a;
};
// file main.cc
#include "A.h"
#include "B.h"
int main(...) {
A a;
}
When you are compiling the .cc file (remember that the .cc and not the .h is the unit of compilation), you need to allocate space for object A. So, well, how much sp...
What's the difference between := and = in Makefile?
...
A simple assignment expression is evaluated only once, at the very first occurrence.
For example, if CC :=${GCC} ${FLAGS} during the first encounter is evaluated to gcc -W then
each time ${CC} occurs it will be replaced with gcc -W.
Recursive assignment =
A Recursive assignment expression is ev...
How to open, read, and write from serial port in C?
... tty.c_oflag = 0; // no remapping, no delays
tty.c_cc[VMIN] = 0; // read doesn't block
tty.c_cc[VTIME] = 5; // 0.5 seconds read timeout
tty.c_iflag &= ~(IXON | IXOFF | IXANY); // shut off xon/xoff ctrl
tty.c_cflag |= (CLOCA...
google mock分享（全网最全最好的gmock文档，没有之一） - C/C++ - 清泛网 ...
...果是一个形参，就是MOCK_METHOD1了，以此往下。
FooMain.cc
#include <cstdlib>
#include <gmock/gmock.h>
#include <gtest/gtest.h>
#include <iostream>
#include <string>
#include "MockFoo.h"
using namespace seamless;
using namespace std;
using ::testing::Return;...
世界首富换人！身价5300亿 却只开一辆破车！ - 资讯 - 清泛网 - 专注C/C++及内核技术
...这位少年实现自己的机会。在做学徒期间他与同样贫困的女裁缝罗萨莉娅·梅拉结了婚。
第一次自己创业
奥特加最初是在拉科鲁尼亚的一家服装店里打工，随后开了自己的裁缝铺，向服装店出售女式上衣。
第一次自己创业是...
Single quotes vs. double quotes in C or C++
...instance:
const uint32_t png_ihdr = 'IHDR';
The resulting constant (in GCC, which implements this) has the value you get by taking each character and shifting it up, so that 'I' ends up in the most significant bits of the 32-bit value. Obviously, you shouldn't rely on this if you are writing plat...
What techniques can be used to speed up C++ compilation times?
...ry. This is a good place for STL headers and other library include files.
ccache is another utility that takes advantage of caching techniques to speed things up.
Use Parallelism
Many compilers / IDEs support using multiple cores/CPUs to do compilation simultaneously. In GNU Make (usually used wi...
2015年硅谷最火的高科技创业公司都有哪些 - 资讯 - 清泛网 - 专注C/C++及内核技术
...il称人类能够在2045年实现数字化永生，他自己也创办奇点大学，相信随着信息技术、无线网、生物、物理等领域的指数级增长，将在2029 年实现人工智能，人的寿命也将会在未来15年得到大幅延长。
国外值得关注的大数据公司都...