我正在查看一些代码,他们有这一行:#define WINVER 0x0501在stdafx.h文件中？你为什么需要定义WINVER？它如何影响您的代码？有人可以解释一下吗？
C#null合并运算符是否有C++等价物？我在代码中进行了太多的空检查.所以正在寻找一种减少空代码量的方法.
我有以下协议缓冲区.请注意,StockStatic是一个重复的字段.
message ServiceResponse
{
enum Type
{
REQUEST_FAILED = 1;
STOCK_STATIC_SNAPSHOT = 2;
}
message StockStaticSnapshot
{
repeated StockStatic stock_static = 1;
}
required Type type = 1;
optional StockStaticSnapshot stock_static_snapshot = 2;
}
message StockStatic
{
optional string sector = 1;
optional string subsector = 2;
}
我在迭代向量时填写StockStatic字段.
ServiceResponse.set_type(ServiceResponse_Type_STOCK_STATIC_SNAPSHOT);
ServiceResponse_StockStaticSnapshot stockStaticSnapshot;
for (vector<stockStaticInfo>::iterator it = m_staticStocks.begin(); it!= m_staticStocks.end(); ++it)
{
StockStatic* pStockStaticEntity = stockStaticSnapshot.add_stock_static();
SetStockStaticProtoFields(*it, pStockStaticEntity); // sets sector and subsector field to pStockStaticEntity by reading the fields using …struct Div
{
int i;
int j;
};
class A
{
public:
A();
Div& divs;
};
在我的构造函数定义中,我有以下内容
A::A() : divs(NULL)
{}
我收到以下错误:
Error72 error C2354:
'A::divs' : initialization of reference member requires a temporary variable
class A
{
bool OutofRange(string& a, string& b, string c);
void Get(vector <string>& str, string& a, string& b);
}
void A::Get(vector <string>& str, string& a, string& b)
{
str.erase(
std::remove_if (str.begin(), str.end(), BOOST_BIND(&A::OutOfRange, a, b, _1)),
str.end()
);
}
我收到的错误如下:
Error 7 error C2825: 'F': must be a class or namespace when followed by '::' File:bind.hpp
Error 8 error C2039: 'result_type' : is not a member of '`global namespace'' t:\3rdparty\cpp\boost\boost-1.38.0\include\boost\bind.hpp 67
有人能告诉我我做错了什么吗？
这就是我现在正在做的事情,但它会锁定文件.
#!/usr/bin/perl
use Env qw( $USERNAME );
use File::Tail;
use strict;
use warnings;
my $file = $ARGV[0];
print "$file\n";
my $fileTail = File::Tail->new( name=>$file, maxinterval=>5, tail=>-1);
my $line;
while ( defined( $line = $fileTail->read ) )
{
print $line;
}
exit;
有人可以为我提供reqExecutions的工作示例吗？我在使用ewrapper和回调机制时遇到了困难.在搜索谷歌的工作示例后,我无法掌握任何简单的工作.请注意,我不是程序员,这就是为什么很难让我的头脑缠绕在ewrapper和回调上.
我计划按行对 data.table 求和并向其添加一个常量。这段代码有什么问题。我专门寻找 pmap_dfr 解决方案：
library(data.table)
library(tidyverse)
temp.dt <- data.table(a = 1:3, b = 1:3, c = 1:3)
d <- 10
temp.dt %>% pmap_dfr(., sum, d) # add columns a b and c and add variable d to it
预期的输出是包含以下行的单列 tibble：
13 16 19
抛出错误：参数 1 必须有名称。
我已经能够让它与 pmap 和 pmap_dbl 一起使用，但在使用 pmap_dfr 时失败。此外，我提供的示例只是一个玩具示例。我希望 d 变量作为 sum 函数的输入参数，而不是稍后将 d 添加到按行求和。
我知道下面的例子会起作用：
temp.dt %>% pmap_dbl(., sum) + d
我想知道#符号是什么意思？为什么要使用它？
例:
INSERT INTO #tmpContracts (sym, contractCount)
SELECT sym,
COUNT(DISTINCT(fulloptionsym)) AS contractCount
如何按名称,年龄和分数对以下代码进行排序...所有三个字段
#include <string>
#include <vector>
#include <algorithm>
struct student_t
{
std::string name;
int age, score;
};
bool by_more_than_1_field( student_t const &lhs, student_t const &rhs )
{
// sort by name, age and score
}
int main()
{
std::vector< student_t > students;
// populate students
std::sort( students.begin(), students.end(), by_more_than_1_field );
}
我找不到一个函数可以总结极坐标数据框中的内容，就像 R 中的一瞥和摘要一样？
假设我有一个xts对象或数据框或csv格式的数据,并希望通过摆脱非流动天数或观察结果小于固定大小的日子来过滤数据(比如说每天观察不到5k) )？我正在按刻度数据操作.
根据社区的要求发布数据.我想在4月5日过滤,因为它的观察次数少于3次:
"DateTime","spy.prices.Open","spy.prices.High","spy.prices.Low","spy.prices.Close"
2007-04-02 09:34:59,142.16,142.34,142.13,142.2
2007-04-02 09:39:59,142.19,142.32,142.14,142.16
2007-04-02 09:44:58,142.16,142.27,142.03,142.25
2007-04-02 09:49:59,142.26,142.28,142.16,142.18
2007-04-02 09:54:57,142.17,142.24,142.15,142.2
2007-04-02 09:59:57,142.2,142.23,142.09,142.13
2007-04-05 14:19:57,144.3,144.34,144.29,144.33
2007-04-05 14:24:59,144.33,144.43,144.31,144.42
2007-04-10 14:34:58,144.64,144.71,144.59,144.62
2007-04-10 14:39:56,144.62,144.69,144.62,144.67
2007-04-10 14:44:59,144.67,144.72,144.67,144.71
2007-04-10 14:49:59,144.7,144.73,144.66,144.73
2007-04-10 14:54:59,144.73,144.75,144.69,144.7
2007-04-10 14:59:58,144.701,144.72,144.7,144.71
2007-04-10 15:04:58,144.72,144.78,144.71,144.74
2007-04-10 15:09:58,144.7499,144.79,144.74,144.77
2007-04-10 15:14:59,144.77,144.7799,144.69,144.69
2007-04-10 15:19:57,144.69,144.73,144.66,144.719
2007-04-10 15:24:59,144.71,144.79,144.71,144.79
2007-04-10 15:29:59,144.79,144.79,144.72,144.725
2007-04-10 15:34:59,144.73,144.79,144.73,144.78
2007-04-10 15:39:57,144.78,144.83,144.76,144.77
2007-04-10 15:44:59,144.78,144.81,144.73,144.77
2007-04-10 15:49:59,144.78,144.78,144.73,144.74
2007-04-10 15:54:57,144.74,144.8,144.73,144.79
2007-04-10 15:59:59,144.79,144.82,144.79,144.8