我的代码的这部分(对于这个项目)给了我一个分段错误.源代码可在此处获得.
void PackageManager::install_package(string pname)
{
if(repository->exists_package(pname)) {
Package *pkg;
ConcretePackage *cpkg;
MetaPackage *mpkg;
if(repository->is_virtual(pname)) {
//code for dealing with meta packages
mpkg = new MetaPackage(pname);
pkg = mpkg;
system->operator+(pname);
} else {
//code for dealing with concrete packages
cpkg = new ConcretePackage(pname);
pkg = cpkg;
system->operator+(pname);
if( cpkg->getDependencies().size() > 0) {
for(set<string>::iterator sit = pkg->getDependencies().begin();
sit!=pkg->getDependencies().end(); ++sit) {
cout<<*sit<<endl;
system->operator+(*sit);
}
}
}
} else {
cout<<"Invalid Package Name"<<endl;
}
}
这是我运行gdb和回溯时的错误.
Program received signal SIGSEGV, …我正在解决一个需要截断输出的问题，令我惊讶的是，我无法找到一种在 java 中截断数字的方法。
输出需要是后跟 6 位小数的数字。
我想要的是
double truncate(double number,int places)输出是
truncate(14/3.0) = 4.666666.
但我得到的是
public static double round(double value, int places) {
if (places < 0) throw new IllegalArgumentException();
long factor = (long) Math.pow(10, places);
value = value * factor;
long tmp = Math.round(value);
return (double) tmp / factor;
}
// rounds( 14/3.0 , 6 ) = 4.666667
随着String.format我得到
String.format("%.6f", 14/3.0) = 4.666667
我还尝试了我在 stackoverflow 上找到的一个解决方案，该解决方案建议使用 BigDecimal 并且给了我相同的答案。
NumberFormat 似乎也以同样的方式工作
java.text.NumberFormat f = java.text.NumberFormat.getNumberInstance();
f.setMinimumFractionDigits(6); …我有一个相对简单的SQL查询拒绝在sqldeveloper上执行,我已经缩小了对此的违规行 -
and (b.date_updated > (sysdate MINUS 2) or a.date_updated > (sysdate MINUS 2))
这是我的where条款的一部分以及其他陈述.
我在视觉上多次对括号进行了计算,它看起来与我平衡,我不确定我在这里做错了什么,有人可以帮我弄清楚这里有什么问题.
为了完整性,这是where子句的样子
where a.customer_id = b.customer_id
and (b.date_updated > (sysdate MINUS 2) or a.date_updated > (sysdate MINUS 2))
and a.c_id = c.c_id
我是iPhone的编程新手,我跟着这本书.我坚持第4章,授权和核心位置的例子.
这是我到目前为止编写的代码:WhereamiAppdelegate.h
#import <UIKit/UIKit.h>
#import <CoreLocation/CoreLocation.h>
@interface WhereamiAppDelegate : NSObject <UIApplicationDelegate, CLLocationManagerDelegate> {
UIWindow *window;
CLLocation *locationManager;
}
@property (nonatomic, retain) IBOutlet UIWindow *window;
@end
这是实现文件:我只包含了我所做的更改.整个文件都在这里.
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
// Create location manager.
locationManager = [[CLLocation alloc] init];
[locationManager setDelegate:self];
[locationManager setDistanceFilter:kCLDistanceFilterNone];
[locationManager setDesiredAccuracy:kCLLocationAccuracyBest];
[locationManager startUpdatingLocation];
[self.window makeKeyAndVisible];
return YES;
}
- (void)dealloc
{
[locationManager setDelegate:nil];
[_window release];
[super dealloc];
}
- (void)locationManager:(CLLocationManager *)manager
didUpdateToLocation:(CLLocation *)newLocation
fromLocation:(CLLocation *)oldLocation
{
NSLog(@"%@",newLocation);
}
- (void)locationManager:(CLLocationManager …我正在尝试创建Point类的一组自定义对象
point.h
#ifndef POINT_H
#define POINT_H
class Point
{
float x_coordinate,y_coordinate;
public:
Point(float x, float y):x_coordinate(x),y_coordinate(y)
{}
float get_x()
{
return x_coordinate;
}
float get_y()
{
return y_coordinate;
}
bool operator==(Point rhs)
{
if( ((int)x_coordinate == (int)rhs.get_x()) && ((int)y_coordinate == (int)rhs.get_y()) )
return true;
else return false;
}
bool operator<(Point rhs)
{
if((int)x_coordinate < (int)rhs.get_x())
return true;
else return false;
}
};
#endif
我刚开始写驱动程序
#include<iostream>
#include<set>
#include "point.h"
using namespace std;
int main()
{
Point p1(-10,-10),p2(-10,10),p3(10,10),p4(10,-10);
set<Point> points_set = set<Point>(); …我有以下代码来读取文本文件.
const string FILENAME = PACKAGES_DIR + pname;
//the arguments to ifstream is a cstring and hence the conversion must be made
ifstream freader;
freader.open(FILENAME.c_str(),ios::in);
if(freader.is_open())
{
while(freader.good())
{
string line;
getline(freader,line);
cout<<line<<endl;
if(line.find("PackageId:"))
{
cout<<line.substr(11)<<endl;
}
else if(line.find("Name:"))
{
cout<<line.substr(5)<<endl;
}
else if(line.find("Version:"))
{
cout<<line.find(8)<<endl;
}
else
{
cout<<line<<endl;
}
}
}
有问题的文本文件的内容是
PackageId:994
Name:basket
Version:1.80-1
Deps:kdebase-runtime,libc0.1,libc0.1-udeb,libc6,libc6-udeb,libc6.1,libc6.1-udeb,libgcc1,libgpg-error0,libgpgme11,libkdecore5,libkdeui5,libkfile4,libkio5,libkparts4,libkutils4,libphonon4,libqimageblitz4,libqt4-dbus,libqt4-network,libqt4-qt3support,libqt4-svg,libqt4-xml,libqtcore4,libqtgui4,libstdc++6,libunwind7,libx11-6,phonon
我得到的输出是
PackageId:994
geId:994
Name:basket
Version:1.80-1
0-1
Deps:kdebase-runtime,libc0.1,libc0.1-udeb,libc6,libc6-udeb,libc6.1,libc6.1-udeb,libgcc1,libgpg-error0,libgpgme11,libkdecore5,libkdeui5,libkfile4,libkio5,libkparts4,libkutils4,libphonon4,libqimageblitz4,libqt4-dbus,libqt4-network,libqt4-qt3support,libqt4-svg,libqt4-xml,libqtcore4,libqtgui4,libstdc++6,libunwind7,libx11-6,phonon
e-runtime,libc0.1,libc0.1-udeb,libc6,libc6-udeb,libc6.1,libc6.1-udeb,libgcc1,libgpg-error0,libgpgme11,libkdecore5,libkdeui5,libkfile4,libkio5,libkparts4,libkutils4,libphonon4,libqimageblitz4,libqt4-dbus,libqt4-network,libqt4-qt3support,libqt4-svg,libqt4-xml,libqtcore4,libqtgui4,libstdc++6,libunwind7,libx11-6,phonon
terminate called after throwing an instance of 'std::out_of_range'
what(): basic_string::substr
我想要的输出是:
PackageId:994
994
Name:basket …我正在尝试检查下面表单中的字段是否已填充,然后才能将其插入数据库,例如显示弹出的字段尚未填写.这只是一个简单的注册表单.
<form name="form1" method="post" action="signup_ac.php">
<strong>Sign up</strong>
Username:<input name="username" type="text" id="username" size="30">
Password:<input name="password" type="password" id="password" size="15">
Name:<input name="name" type="text" id="name" size="30">
<select name="Month">
<option selected>Month</option>
<option value="January">January</option>
<option value="Febuary">Febuary</option
</select>
<select name=Year>
<option selected>Year</option>
<option value="2012">2012</option>
<option value="2011">2011</option>
</select>
<input type="submit" name="Submit" value="Submit">
<input type="reset" name="Reset" value="Reset">
</form>
我如何使用JavaScript或jQuery执行此操作.
我的代码面临着一个非常奇怪的问题,我无法将元素推入列表中.
我正在尝试实现扫描填充算法.我想要在屏幕上绘制的点列表,以便我可以检查扫描线是否与它们相交.在我的Screen :: plot_pixel函数中,我将Point推入mapped_points列表.但是当我遍历列表时,它是空的.(我正在使用友元函数迭代shape.cpp)
我尝试使用套装但无济于事.我已经附加了控制台输出我也得到了.
plot_pixel被多次调用,我通过在那里添加一个print语句验证了这一点但是这些点拒绝被推入.这是我的所有代码,point.h
#ifndef POINT_H
#define POINT_H
class Point
{
float x_coordinate,y_coordinate;
public:
Point(){}
Point(float x, float y):x_coordinate(x),y_coordinate(y){}
float get_x() const{return x_coordinate;}
float get_y() const {return y_coordinate;}
bool operator==(const Point rhs)const
{
if( ((int)x_coordinate == (int)rhs.get_x()) && ((int)y_coordinate == (int)rhs.get_y()) )
return true;
else return false;
}
bool operator<(const Point rhs)const
{
if((int)x_coordinate < (int)rhs.get_x())
return true;
else return false;
}
};
#endif
screen.h
#ifndef SCREEN_H
#define SCREEN_H
#include<graphics.h>
#include "point.h"
#include<list>
class Shape;
class Screen
{ …