dereference

问题 I'm trying something very simple, well supposed to be simple but it somehow is messing with me... I am trying to understand the effect of ++ on arrays when treated as pointers and pointers when treated as arrays. So, int main() { int a[4] = { 1, 4, 7, 9 }; *a = 3; *(a+1) = 4; *++a = 4; //compiler error } 1: So at *(a+1)=4 we set a[1]=4; //Happy But when *++a = 4; , I'd expect pointer a to be incremented one since ++ is precedent to * and then * kicks in and we make it equal to 4. But this

问题 I'm learning how to use Qt with PyQt, and I have a QTabelView with a StandardItemModel I've populated the model successfully and hooked up the itemChanged signal to a slot. I'd l'd like to mess around with whatever object is returned in IPython, so currently I have the line: def itemChangedSlot(epw, item): new_data = item.data() print new_data print item which prints <PyQt4.QtGui.QStandardItem object at 0x07C5F930> <PyQt4.QtCore.QVariant object at 0x07D331F0> In the IPython session is it

问题 I'm learning how to use Qt with PyQt, and I have a QTabelView with a StandardItemModel I've populated the model successfully and hooked up the itemChanged signal to a slot. I'd l'd like to mess around with whatever object is returned in IPython, so currently I have the line: def itemChangedSlot(epw, item): new_data = item.data() print new_data print item which prints <PyQt4.QtGui.QStandardItem object at 0x07C5F930> <PyQt4.QtCore.QVariant object at 0x07D331F0> In the IPython session is it

问题 I'm learning how to use Qt with PyQt, and I have a QTabelView with a StandardItemModel I've populated the model successfully and hooked up the itemChanged signal to a slot. I'd l'd like to mess around with whatever object is returned in IPython, so currently I have the line: def itemChangedSlot(epw, item): new_data = item.data() print new_data print item which prints <PyQt4.QtGui.QStandardItem object at 0x07C5F930> <PyQt4.QtCore.QVariant object at 0x07D331F0> In the IPython session is it

问题 In the hope of gaining a better understanding of the answers given in this post, can someone please explain to me if the following circular buffer implementation is possible, and if not, why not. #define CB_TYPE_CHAR 0 #define CB_TYPE_FLOAT 1 ... typedef struct CBUFF { uint16 total; /* Total number of array elements */ uint16 size; /* Size of each array element */ uint16 type; /* Array element type */ uint16 used; /* Number of array elements in use */ uint16 start; /* Array index of first

问题 I am trying following hql query to execute SELECT count(*) FROM BillDetails as bd WHERE bd.billProductSet.product.id = 1002 AND bd.client.id = 1 But it is showing org.hibernate.QueryException: illegal attempt to dereference collection [billdetail0_.bill_no.billProductSet] with element property reference [product] [select count(*) from iland.hbm.BillDetails as bd where bd.billProductSet.product.id=1001 and bd.client.id=1] at org.hibernate.hql.ast.tree.DotNode$1

问题 In PHP, the following code is valid $a=array(0);$a[0]; but that one is invalid: array(0)[0] What is the terminology corresponding to that behaviour? (has it anything to do with "dereferencing"?) What is the motivation behind such a behaviour (besides user spite :-P) I am looking for the general terminology , not necessarily the terminology associated with PHP. (Other example: in MATLAB, the following is valid: s = size(M) s(0) but that is invalid: size(M)(0) In both PHP and MATLAB, adding

问题 The standard says that dereferencing the null pointer leads to undefined behaviour. But what is "the null pointer"? In the following code, what we call "the null pointer": struct X { static X* get() { return reinterpret_cast<X*>(1); } void f() { } }; int main() { X* x = 0; (*x).f(); // the null pointer? (1) x = X::get(); (*x).f(); // the null pointer? (2) x = reinterpret_cast<X*>( X::get() - X::get() ); (*x).f(); // the null pointer? (3) (*(X*)0).f(); // I think that this the only null

问题 I'm new to programming and I'm trying to wrap my head around the idea of 'pointers'. int main() { int x = 5; int *pointerToInteger = & x; cout<<pointerToInteger; } Why is it that when I cout << pointerToInteger; the output is a hexdecimal value, BUT when I use cout << *pointerToInteger; the output is 5 ( x=5). 回答1: * has different meaning depending on the context. Declaration of a pointer int* ap; // It defines ap to be a pointer to an int. void foo(int* p); // Declares function foo. // foo

问题 I am answering a textbook question from this textbook. I am learning about pointers in C and have come across l-values and r-values. From my understanding: l-values are values that are defined after they are executed (++x) r-values are values that are not defined after they are executed (x++) It that correct? The question I wanted to answer (with my attempts): a) Which of the following C expressions are L-Values? 1. x + 2 Not a L value 2. &x Is a L value 3. *&x Is a L value 4. &x + 2 Not a L