小编Eri*_*ric的帖子

是否有可能构建一个循环git历史,如下面的ascii-art？

A (root)
|  H<-G
| /    \
VL      \
C        F
 \      /
  \    /
   D->E

凡C被合并提交的A和H,但H本身就是一个后代C

给定两个2D向量,如何判断第二个向右(顺时针)第一个,还是向左(逆时针)？

例如,在这些图中,B是A的右侧(逆时针)

A   B   .       .----> A
^  ¬    |\      |   
| /     | \     |  
|/      V  \    V 
.       B   A   B

说我有这个班:

class MyString(str):
    def someExtraMethod(self):
        pass

我希望能够做到

a = MyString("Hello ")
b = MyString("World")
(a + b).someExtraMethod()
("a" + b).someExtraMethod()
(a + "b").someExtraMethod()

1. 按原样运行:

   AttributeError: 'str' object has no attribute 'someExtraMethod'
   

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2. 显然这不起作用.所以我补充一下:

   def __add__(self, other):
       return MyString(super(MyString, self) + other)
   def __radd__(self, other):
       return MyString(other + super(MyString, self))
   

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   TypeError: cannot concatenate 'str' and 'super' objects
   

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3. 嗯,好的.super似乎不尊重运算符重载.也许:

   def __add__(self, other):
       return MyString(super(MyString, self).__add__(other))
   def __radd__(self, other):
       return MyString(super(MyString, self).__radd__(other))
   

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   AttributeError: 'super' object has no attribute '__radd__'
   

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仍然没有运气.我该怎么办？

我只是在JavaScript中遇到了一些符号:

var a = (1,2,3,4,5);

在上述情况下,这将始终返回最后一个值5.我知道使用括号来命名我的JavaScript代码,但从未见过它以这种方式使用.

这种符号有什么用处,还是只是一些JavaScript副产品？

我有一些这样命名的常量:

template<int n> class usart {
private:
    usart();
public:
    enum class tx {};
    enum class rx {};
    enum class ck {};
};

template<> class usart<1> {
public:
    enum class tx { A9  = gpio::A9,  C4 = gpio::C4 };
    enum class rx { A10 = gpio::A10, C5 = gpio::C5 };
    enum class ck { A8  = gpio::A8 };
};

// two more of these

where gpio只是一个简单的整数枚举.

我想在另一个文件中对我的类强制执行某些类型的安全性:

class USART {
public:
    template<int N>
    USART(typename usart<N>::tx pin_tx, typename usart<N>::rx pin_rx) { …

这段代码:

constexpr uint32_t ticksPerSecond = 100000;

struct ticks {
    uint32_t count;
    template<typename integer>
    constexpr explicit ticks(integer c) : count(c) { }
    explicit inline operator float() {
        return count / (float) ticksPerSecond;
    }
};

template<>
constexpr explicit ticks::ticks<float>(float s) : count(s * ticksPerSecond) { }

给我错误:

timer.hpp:(last line of snippet):
error: only declarations of constructors can be 'explicit'

肯定ticks::ticks 是构造函数？

int.__hash__简单地返回值似乎是合理的。果然，这似乎是CPython实现它的方式：

>>> hash(1)
1
>>> hash(2)
2
>>> hash(123456789)
123456789
>>> hash(-123456789)
-123456789

好吧，这对于所有大多数整数x都成立吗？

>>> [x for x in range(-10000, 10000) if hash(x) != x]
[-1]

?？

>>> hash(-1)
-2

为什么是-1该规则的例外？

这段代码

struct T {
    int m_x;
    T(int x) : m_x(x) {}

    operator T() {
        return T(0);
    }
};

int main() {
    volatile T v(2);

    T nv(1);
    nv = v; // nv.m_x = 0
}

给出：

prog.cpp: In function ‘int main()’:
prog.cpp:14:10: error: no match for ‘operator=’ in ‘nv = v’
prog.cpp:14:10: note: candidates are:
prog.cpp:1:8: note: T& T::operator=(const T&)
prog.cpp:1:8: note:   no known conversion for argument 1 from ‘volatile T’ to ‘const T&’
prog.cpp:1:8: note: T& T::operator=(T&&)
prog.cpp:1:8: note:   no …

i686-linux-gnu-gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv
-O2 -Wall -Wstrict-prototypes -fPIC -I/usr/include/python2.7 -c src/re2.cpp -o build/temp.linux-i686-2.7/src/re2.o
cc1plus: warning: command line option ‘-Wstrict-prototypes’ is valid for C/ObjC but not for C++ [enabled by default]
src/re2.cpp:201:29: fatal error: re2/stringpiece.h: No such file or directory
 #include "re2/stringpiece.h"
                             ^
compilation terminated.
error: command 'i686-linux-gnu-gcc' failed with exit status 1

我以前做过 sudo apt-get install python-dev

我正在尝试为以下方案创建一个javascript对象

一项调查采访了多人关于他们在几顿饭中消费的食物.该对象需要嵌套如下: -

case={}
case[x].Interview={}
case[x].Interview[y].meals={}
case[x].Interview[y].meals[z].Food=[]

我通过以下代码实现了这一点

var $caseoffset=0
loadcases()
function loadcases() {
    $.ajax({
        url: "functions.php",data: {offset: $caseoffset,method: "getCase"},method: "post",dataType: 'json',
        success: function(result) {
            cases = result;
            loadinterview(cases[$caseoffset].fldCaseID)         
        }
    })  
}

function loadinterview($CaseID) {
    $.ajax({
        url: "functions.php",
        data: {method: "getinterview",caseid: $CaseID}, method: "post",dataType: 'json',
        success: function(result) {
            thiscase=cases[$caseoffset]
            thiscase.interviewcount=result.length
            thiscase.interviews={}

            $.each(result,function(key,val){
                thiscase.interviews[val.fldInterviewID]=val
                loadmeals(val.fldInterviewID)
            })  
        }    
    })
}
function loadmeals($InterviewID) {
    $.ajax({
        url: "functions.php",
        data: {method: "getmeal",InterviewID: $InterviewID},method: "post",dataType: 'json',
        success: function(result) {
            thiscase.interviews[parseInt($InterviewID)].mealcount = result.length
            thiscase.interviews[parseInt($InterviewID)].meals={}

            $.each(result, function(key, val) …