Visual C++ :: Overriding Prefix / Postfix Operators
Oct 26, 2012
I have an assignment which includes overriding the prefix and postfix operators, and my teacher has provided what the output from the program should be. I've written the code and it's nearly perfect, except for one tiny error I can't seem to get right.
This is (most of) the code from the header--I left out a few of the parts that aren't relevant to my question:
Code:
using namespace std;
#include<string>
#include<iostream>
class NumDays {
private:
int hours;
[Code] ....
The two problem lines are supposed to be outputting 12 and 1.5, respectively, but are instead showing 13 and 1.625. I know that hours is being changed to 12 at the end of the overriden prefix operation in the line above them, so I don't understand why it returns to 13 again. What I need to change?
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Apr 25, 2013
first code,
Code:
int aRRay[] = {2,4,8,-2,-1,100};
int *ptr;
int loop;
ptr = &aRRay[0];
}
[code].....
first code result, " aRRay[] " and " ptr + loop " are in the same result
second code result, " aRRay[] " and "ptr + loop " are in the same result too,
third code result, " aRRay[] " and "ptr + loop " are in the same result Except "aRRay[4] = -1 with ptr + 4 = 100 " and "aRRay[5] = 100 with ptr + 5 = 14"
Question:Why the third code had a different result ? Its only because of the increment ++ptr or the round brackets on the *(++ptr) ?
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May 2, 2013
The objective is to build a month class that hold data on the number of the month and the name of the month. Using constructors and overloads, set it up to where you can input either the month or the name and it will output the results for both the month number and name.
Here is the code I have so far:
#include<iostream>
#include<string>
using namespace std;
class Month{
private: string name;
int monthNumber;
[Code] ....
It is almost fully compiled if I go by the error list. The only problems I see to be having are with the prefix and postfix overloads.
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Jun 14, 2014
I'm experimenting with a custom memory-pool for my application, and I initially planned to override the global new and delete operators to allocate memory in this pool. But since I'm using QT, this will apply to all the QT-related stuff as well. Should I instead just override the new and delete operators per class?
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Jul 24, 2014
[URL]
class CMyclass
{
public:
CMyClass(BOOL bUseWhichMemManager);
void* operator new(size_t);
void operator delete(void*);
};
I create two memory manager called CMemManager1 and CMemMangaer2, using different algorithms to allocate buffer. Now I want to control which memory manager to be used, when calling new.
I try to add a parameter bUseWhichMemManager to the constructor, but in overrided new function, there are no way to access the parameter. Is there a way to pass more parameters to new operator, such as:
void* operator new(size_t size, BOOL bUseWhichManager);
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Oct 8, 2012
I have subclassed CFileDialog. I need to select both file and folder on certain case only. Suppose I have a folder selected and it is containing desired file type. Then in such situation, On clicking open button will not open the selected folder. But just close the CFileDialog with IDOK.
For doing this I need to provide my own implementation for Open button handler. I am not getting how I can do this.
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Oct 31, 2013
There was an "impovement" since Windows 7 in algorithm for selecting the initial directory, which is described here OPENFILENAME structure. Briefly:
Windows 7:
If lpstrInitialDir has the same value as was passed the first time the application used an Open or Save As dialog box, the path most recently selected by the user is used as the initial directory. Otherwise, if lpstrFile contains a path, that path is the initial directory.
Otherwise, if lpstrInitialDir is not NULL, it specifies the initial directory. If lpstrInitialDir is NULL and the current directory contains any files of the specified filter types, the initial directory is the current directory. Otherwise, the initial directory is the personal files directory of the current user. Otherwise, the initial directory is the Desktop folder.
The problem that this behavior is not what users of my program expect. Another constraint is that I need to use old CFileDialog dialog, not Common File Dialogs. I've tried to use advises described on StackOverflow and on MSDN. This solution by EllisMiller works perfectly:
Specifying a full path (including filename) in lpstrFile. The filename of course shows up in the filename box which is annoying. I ended up using a filename of "." and adding a bit of code to clear the filename combobox once the dialog is open.
BUT I can't figure how to clear the filename combobox. I've tried to add hook procedure, enumerate windows and clear text, but this didn't work for me. So, my question is: how can I clear text in the filename combobox of CFileDialog?
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Sep 25, 2013
the question am having problems with..
1.Write a class function that defines adding, subtracting, multiplying and dividing fractions by overloading standard operators for the operations.
2. Write a function member for reducing factors and overload I/O operators to input and output fractions. how would i set this up?
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Sep 16, 2013
Code:
#include<stdio.h>
#include<conio.h>
#include<string.h>
#include<ctype.h>
#define MAX 50
[Code] ....
[URL] .....
My output should look like this ..
Enter an expression in infix form: (9+6)/(2*4)^15
Specify output expression type,1) Prefix 2)Postfix
The Prefix expression is: /+96^*2415
----------------------------------------------
Enter an expression in infix form: (9+6)/(2*4)^15
Specify output expression type,1) Prefix 2)Postfix
The Postfix expression is:96+24*15^/
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Feb 4, 2014
I am writing the overloading operator function (prefix ++) according to my book.. but it doesnt work !!!!!!
But if i write:
void operator++() {
++x;
}
It works !!!!!
Here is my code according to the book that doesnt work as it should:
#include <iostream>
using namespace std;
class things {
int x,y,z;
[Code] ....
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Jan 17, 2014
I have some functions inlined using the inline function prefix. If the function is called from outside the file (so a seperate psp-gcc -O3 ... filename.c filename.o compile command, when only the function is changed), will the other files be updated too? (I'm using the pspsdk toolchain).
Example:
max.c
inline byte max(byte a, byte b) {
return a>b?a:b;
} use1.c
void use1() {
if (max(1,2)==0)
[Code] ....
If I compile this, next change the max function and recompile using make (the compiler only takes the changed max.c->max.o file, next links them together) will use1.c&use2.c be updated with the new max.c function?
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Feb 5, 2013
I've got the following code with output. I can't figure out myself why it's what printed out there. I believe, it has something to deal with overloading/overriding/virtual functions implementations in C++:
class Base{
public: virtual void f(int);
virtual void f(double);
}
[Code].....
Thus here're my conclusions:
1) in line
d.f(1.0);
for some reason compiler preferred casting double->int of the argument and then call to 'Derived::f(int)'.
2)in line
pb->f(1.0);
for some reason compiler preferred call to 'Base::f(double);'. 'Base' is static type of pb, but the dynamic type is 'Derived'.
I believe the answer has to deal with the fact whether virtual table contains in addition to functions' names also the types of arguments they accept. AFAIK, vTable doesn't include such info.
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Feb 15, 2013
Is it possible to do something like this:
class A //parent {
public:
virtual void DoSomething() = 0;
};
class B : public A //child {
public:
void DoSomething(string s) override;
}
Where the child member function overrides and changes the parents member function.
I need to pass an array of key states to the Controller class' Update() function but don't want to send it to every class derived from Object (like Controller).
Is this possible or do I have to overload the original Update() member function (but I would need to define the method in Object then (i.e remove the pure virtual function (=0)))
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Mar 20, 2013
Below is simplified code consists of two classes, namely Parent and Child.
Child is inherited from Parent.
All member functions of class Parent are declared virtual, and they have been overridden in the class Child.
Code 1:
#include <cstdlib>
#include <iostream>
using namespace std;
#define QUANTITY 5
class Parent {
[Code] ....
The output of the code:
Child::showID() -- ID is 1804289383
Child::showID() -- ID is 846930886
Child::showID() -- ID is 1681692777
Child::showID() -- ID is 1714636915
Child::showID() -- ID is 1957747793
Parent::operator=() invoked.
Child::showID() -- ID is 1804289383
Child::showID() -- ID is 846930886
Child::showID() -- ID is 1714636915
Child::showID() -- ID is 1714636915
Child::showID() -- ID is 1957747793
Question:
Why is Parent::operator= invoked instead of Child::operator= ..?
Isn't it already declared virtual and hence would be overridden..?
I need to invoke Child::operator= instead. How to achieve this?
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Dec 27, 2012
I'm looking at writing my own plug-in app, but I know that deleting class instances that were created in a plug-in module can result in the dreaded "undefined behaviour" because of the different memory spaces. Many examples of plug-ins use create_class and destroy_class functions to resolve this problem, but I wondered about overriding / overloading the class's new and delete operators. This would be used for all third-party library class derivations (e.g. derived GUI classes) and all home-grown classes.
The operators would only be declared in the class declaration:
class PluginBase {
public:
void *operator new(std::size_t n);
void operator delete(void *p);
// Other plugin bits
While the actual implementation would be defined in the plug-in's implementation file:
#include "PluginBase.h"
void *PluginBase::operator new(std::size_t n) {
return ::operator new(n);
[Cvoid PluginBase::operator delete(void *p) {
return ::operator delete(p);
}
This would need to be implemented in every transferable plug-in class (possibly by a crafty IMPLEMENT_PLUGIN(classname) macro or some other mechanism), but before I commit this to my code I was hoping for feedback. Does this sound like a good idea? The GUI classes in particular are handled by a third-party library, so it's some memory-space safe way of deleting them by the GUI library (in the app) that I'm looking for.
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Jan 22, 2015
PHP Code:
class B {
public:
template<class T>
T foo(){}
};
class D1:public B {
[Code] ....
I have that code piece and would want it to work but it doesn't.
Error "Error2error C2993: 'double' : illegal type for non-type template parameter '__formal' ....
I have no choice and have to use double and float for template typename when specializing. I tried to wrap it up like this
PHP Code:
typedef struct DOUBLE {
DOUBLE(double d){ val = d; }
double val;
};
but it's of no use.
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Feb 15, 2015
My program suppose calculate postfix expression.
Ex. 5 4 + 3 10 * + the answer is 39 because if I change it to infix, it's (5 + 4) + (3 * 10)
I need to use vector to compute the value. Here is what I think. First, I save leftmost from the string. If it is a number, I push. If that is a operation, I pop twice and push the result. By doing it until the string is emptied, the vector will only contain the final answer. And here is my code
#include <iostream>
#include <vector>
#include <string>
using namespace std;
int main(){
vector<int> stack;
string input;
[Code] .....
When I put 1 1 + or 2 2 +, it showing me a correct answer, but when I put the above example which is 5 4 + 3 10 * +, it shows 30 instead of 39.
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Sep 14, 2014
I'm trying to make an infix to postfix notation calculator. The difficult thing is th stack class is custom. It's not to hard to understand, I don't know if the fact that it is that way will not allow me to receive support. The difference is that the pop functions is as such:
stack<char> conversion;
char temp;
conversion.pop(temp);//It receives a parameter and puts the popped element in there.
conversion.peek(temp);//Places the top element in said parameter
not only that... but these are boolean functions. they return true if the operation was completed. So they can be used as conditions.
#include<iostream>
#include<string>
#include<stdio.h>
#include"stack.h"
using namespace std;
int main(void) {
Stack<char> conversion;
string infix,inter,temps;
[Code] .....
The error is that i am mismanaging parenthesis handling and i can't seem to grasp where and how.
An example input is:(35+7)-(9-2)
that input gives me:35 7 + 9 2 ) -
but another input such as :(35+7)/7
outputs as: 35 7 + 7 /. Totally fine.
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Mar 8, 2013
I am Getting following errors I don't know why.I have mentioned the lines (in comments) where these errors are occurring.
__________________________________________________
warning C4018: '<' : signed/unsigned mismatch
error C2064: term does not evaluate to a function taking 0 arguments
error C2064: term does not evaluate to a function taking 0 arguments
__________________________________________________ _
Code:
/////////////////////////////////////////////////
//libraries
/////////////////////////////////////////////////
#include <iostream>
#include <string>
using namespace std;
[Code] .....
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Oct 1, 2013
Program which convert expression from PostFiz to Infix and also wants to evaluate them....
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Nov 3, 2013
i feel like im really close to completing this but i cant seem to get the result printed out i dont think im calling my evaluate function correctly and its not performing the operations..
#include <iostream>
#include <stack> //stack header file
using namespace std;
[Code].....
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Jul 27, 2012
Recently, i successfully overloaded postfix operator to class counter by using Object and Class. Now, i want to overload same postfix operator to Inheritance. I created my code and generated in compiler. But, my compiler signaled me uncommon error(saw first time) and i couldn't generate any idea where my actually mistake is.
Here is my Code which objective is to count the number increasingly or decreasingly as per object created of CountDn class.
Code:
#include <iostream>
using namespace std;
class Counter // base class
{
protected : // NOTE : Not Private
unsigned int count;
[Code] ....
Error :|41|error: no 'operator++(int)' declared for postfix '++', trying prefix operator instead|
|42|error: no 'operator++(int)' declared for postfix '++', trying prefix operator instead|
|42|error: no match for 'operator=' in 'c2 = c1.CountDn::<anonymous>.Counter:perator++()'|
|44|error: no 'operator--(int)' declared for postfix '--', trying prefix operator instead|
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Nov 21, 2014
So I have been working my way through this assignment and I'm just stuck now. I cannot get this work properly It just tells me I'm trying to return a local variable when attempting to return postfix in the to_postfix function. It is line 97 that wont compile. Also I cannot change anything in runner.c.
Calculator.c
Code:
1 #include <stdio.h>
2 #include <stdlib.h>
3 #include <ctype.h>
4 #include <string.h>
5 #include "stack.h"
[Code] .....
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Dec 14, 2013
i try to write a postfix calculator program using stack in C++ the in put must be the infix expression but can dont know how to write a infix expression in put.
this is my code :
#include <iostream>
#include <stdio.h>
#include <math.h>
#include <conio.h>
using namespace std;
}
[code]....
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Feb 6, 2014
So i solved my earlier problem but now how do i make it read from the text file that i have and output the postfix notations? Because right now it is only outputting what is currently in the text file for example
6+9
2+7*8
(1+5)*3
5+(6-2)*((2-8)
Header file is
#ifndef STACKS_H
#define STACKS_H
#include <iostream>
using namespace std;
const int STACKS_CAPACITY = 128;
typedef int StacksElement;
[Code]...
test client cpp is
#include <iostream>
using namespace std;
#include "Stacks.h"
#include <fstream>
#include <string>
#include <cassert>
#include <cctype>
[Code]...
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Apr 12, 2015
I am trying to convert from infix to postfix, and then evaluating the postfix expression to get the final answer. I am having a severe problem though, because for somereason the conversion is not working at all. For example, when I input the first infix expression:
24 + 33 * ( 7 - 5 ) + 8 / 3 it ouputs 24 33 7 5 - 5 ) + 8 / 3( 7 - 5 ) + 8 / 3* ( 7 - 5 ) + 8 / 3+ 33 * ( 7 - 5 ) + 8 / 3 8 3/ 3+ 8 / 3
Which is obviously very wrong. I am not really sure where the problem is though.
Below I have included all of the code needed. I also had to create my own stack class, so I will include it too .
#include "stacks.h"
#include <iostream>
using namespace std;
bool IsOperand(char C) {
if(C >= '0' && C <= '9') return true;
if(C >= 'a' && C <= 'z') return true;
[Code] .....
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