Came across the foll code:
#include<stdio.h>
main() {
int i=4,j=7;
j=j||(printf("you can")&&(i=5));
printf("%d %d",i,j);
}
output: 4 1
Although I am specifying the braces for the && operator so that it gets executed first..Then also the value of i remains 4 only..Why does not it gets changed to 5??Also the printf does not execute??
I am using VS2K12 version 4.5.50709.
I am working Prata's C++ Primer 6ed. The exercise sequence of Listing 6.9 through Listing 6.11 involved using a switch statement with integer input (switch.cpp: 6.9), character input (switchchar.cpp: 6.10), and using integer input with enum (enum.cpp: 6.11). The main function of each was similar, especially in the usage of the input variable used by cin ("code" in the code provided below).
With switch.cpp, it was shown that entering a character caused the loop to cycle continuously. This was because the "cin >> choice" call failed to read the character into the int (choice) variable. The 'cin.fail() test followed by cin.clear().get() was added to switch.cpp to prevent the bad read from producing the loop spin.
However, in the original version of enum.cpp (below), which also uses integer input, if I input an 'm', the response is:
Enter color code (0-6): m
Bye!Press any key to continue . . .
In other words, with character input the int based read operation apparently did not fail. The main methods were very similar, but I noticed that switch.cpp used the "!=" operator in the while loop's test expression. So I tried it in enum.cpp and it is commented out in the code below. I found that with that code in place the inability to handle character input was present. When a character is input the failing response is:
Enter color code (0-6): Always include default case.
Enter color code (0-6): Always include default case.
Enter color code (0-6): Always include default case.
...
...
I assume this is a VS2K12 quirk, but I will likely try something like gcc at work tomorrow. I think it would be easy to chase this though the iostream code, for someone who has already been there. But it is going on 1AM, and I am not certain it would be time well spent (i.e. how often do you "really" need to debug iostream code?). I did use the debugger and see that (I believe) _OK is set to false.
// enum.cpp -- Listing 6.11 (PG 279): Using enum (091513)
#include <iostream>
// const int red = 0, orange = 1, ....
enum {red, orange, yellow, green, blue, violet, indigo};
int main() {
using namespace std;
int code;
[code].....
If I have the following code:
long lSecondsSum = 8039;
double dNumDays = lSecondsSum / (24 * 3600);
I expect to get 0.093044 but for some reason I am getting dNumDays = 0.0000000000.
However, if I write the code as follows:
long lSecondsSum = 8039;
double dNumDays = lSecondsSum/24;
dNumDays = dNumDays/3600;
then I get correct dNumDays = 0.092777777777777778.
Also, how do I avoid all these floating point errors.
The + operator has left to right associativity then for the program f1() + f2(), why f1() is not called first compared to f2()?
View 5 Replies View RelatedI wrote this program using an online compiler i am getting a lot of errors.
#include <iostream>
#include <string>
#include <sstream>
using namespace std;
int main() {
string birthmonth;
string birthday;
[Code] ....
I have a code that uses multi threads using OMP. However, Inside the code I allocate too many memory using "new".
I know that the memory allocation using new must be done in serial. Therefore I am not getting a good performance out of the multi-threaded program.
I thought about allocating a big memory only once, and then advance the pointer every time I need to allocate a small memory.
For example, if I need to allocate chunks of 7 doubles:
Code:
main_memory = new double [10000];
double* x1 = main_memory;
main_memory+= 7;
double* x2 = main_memory;
main_memory+= 7
However, I do not know how to handle the memory deallocation. Beside, this is not thread safe method because main_memory is shared by all threads.
May be there is a boost library that does this, which I am not aware of.
I have two class GameOfLife and Cell and i want to overload square braket for class GameOfLife."if g is a GameOfLife object, g[10][5] will return the Cell at row 10 and column 5. If there is no such Cells, then it will return a new Cell with position (-1000,- 1000)."
but if g[10][1000] and 1000>cols,then it returns different Cell exp (3,2) How i do control the col ( [row][col] )?
Code: vector<Cell> GameOfLife::operator [](const int row){
vector<Cell> rowCell;
for(int i=0; i<cols; ++i)
{
if( isLive(row,i) )
rowCell.push_back( Cell(row,i) );
else
rowCell.push_back( Cell(-1000,-1000) );
}
return rowCell;
}
Switch case statements are a substitute for long if statements that compare a variable to several "integral" values ("integral" values are simply values that can be expressed as an integer, such as the value of a char).
So does that mean switch statements can only test if variable == value and nothing more, like > < >= <= != etc... ? I tried to make a program to test this and it seems like switch statements are limited to == but I'm not sure, maybe I'm doing something wrong.
This is the program I tried to make to test this:
Code:
#include <stdio.h>
int main () {
int n;
[Code]....
So is it true that switch statements only work with the built in == operator? if that was the case then I would feel rather meh about switch statements.
I have a small piece of code that used the set::insert function on a set of myClass. For that, I need to overload the < and > operators, which I have, but I still get a huge error saying it can't compare.
set<MyClass> mySet;
MyClass myClass
All the class information gets filled in. Then, I try to insert...
mySet.insert(myClass);
bool operator<(MyClass &lhs, MyClass &rhs) {
return lhs.name < rhs.name; //name is a string
}
The error says
...stl_function.h:230:22: error: no match for 'operator<' in '__x < __y'
MyFile.h:80:6: note: candidate is bool operator<(MyClass&, MyClass&)
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?
View 2 Replies View RelatedI have two files NumDays.h and ClientProgram.cpp
clientprogram.cpp basically has the main module below
int main(){
// Initialized UDT object Declarations
NumDays hoursWorked_John; // Instantiate with Default Constructor
NumDays hoursWorked_Sue(36.9); // Instantiate with Initializing Constructor
NumDays hoursUsed_Sue(4.5); // Instantiate with Initializing Constructor
[Code] .....
I can't figure out anything to put in for NumDays.cpp so it's not there.
In the following program.
void main() {
int a=1;
cout<<a++<<" "<<++a<<" "<<a++<<endl;
}
If I execute the above program i should get 1 3 3. But I'm getting different values when I executed this program. The values that I get after execution are 3 3 1.
I made a program that allows the user to enter information of credit cards on an array of size 5, however I need to allow the user to compare the five credit cards with each other and I am having problems with this particular part. I made my bool operator functions for the operator< and the operator> but how to make the user be able to select which cards he wants to compare and how to compare them. My code is the following:
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
const int SIZE = 5;
enum OPCIONES {CARGAR=1, ABONAR, NADA};
[Code] ......
Why can't I take the address of operators for primitives?
#include <iostream>
#include <string>
int main()
{
{
std::string (&plus)(std::string const&, std::string const&) = &std::operator+;
std::string a ("Hello, "), b("World!");
std::cout << plus(a, b) << std::endl;
[Code]...
[URL]....
I'm using this functionality in a templated class, do I really have to specialize for primitives or use std::enable_if?
What I'm trying to do is create a class for constructing an 'op tree' for parsing infix notation.
I started with a base class that uses a map of lambdas to actually calculate the operations (since they are mostly 1 line functions) of passed in integer or float values.
This base class just uses a templated T type as the lvalue and rvalue. I realized though that if I overload the math operators, +, -, etc.. I could also use the class itself as a type for the lvalue and rvalue. This lead me to think I could easily create the op tree by using Operation class members themselves as operands, which I think makes sense but I'm having some trouble expressing the code.
Heres what I have thus far
Code:
#include <map>
#include <string>
#include <algorithm>
#include <iostream>
namespace Calc {
[Code] .....
Example, if you look at the main() function I create normal operations easily with integer values. I then try to create a "tree" operation that includes 2 sub-operations as it's rvalue and lvalue, that is where I'm having some conceptual problems as far as implementing the code to do that.
what order a CPU would process the following arithmetic problem: 5 - (-9) = 14? Would the CPU recognize that the 'minus a minus' combination simply represents 5 + 9, and proceed with that addition, or would the CPU have to first calculate the 2's complement of -9, and then proceed to take the 2's complement of that first result in order to complete the calculation of the addition of the 'double negative'?
View 2 Replies View Related1.The operands from << and >> may be any of integer type (including char) The integer promotions are performed on both operands the result has the type of the left operand after promotion.
It means that if we have z = x >> y then sizeof(z) == sizeof(x) ?
2. The ~ operator is unary the integer promotions are performed on its operand.
So if I have short int y; and int x=1; y = ~x what is the meaning here?
I'm having an issue with output, luckily everything else works!! I'm working with Mixed Numbers and operations on them. So, here's the code I'm testing with:
int main() {
Mixed m1(5), m2(1,1,1), m5(2,2,3);
cout << "m1+m2= " << m1+m2 << endl;
cout << "m1 + 10=" << m1+10 << endl;
cout << "m1 - 10=" << m1-10 << endl;
return 0;
}
And here is the output for that code:
File name: fract.h
#ifndef fract_H
#define fract_H
#include <iostream>
using namespace std;
const int DEFAULT_VAL = 0;
[Code] ....
The code below doesn't compile. Two things to clear up:
1) I know x is going to be garbage.
2) I used the same type name label ElementType.
#include <iostream>
#include <ostream>
template <typename ElementType>
class Example {
[Code] .....
I must overload [] but at the same time I must use polymorphism. I wonder if using polymorphism affects operators overloading since when I modified the first class by writing "virtual":
virtual void mostrarDatos(char*, char*, char*);
virtual void calcularEdad(int);
So I can do the polymorphism, it affects the part of the code where suppose to do an addition:
s=student1+=student2;
t=student3+=student4;
u=s+=t;
if I do that, it shows some strange numbers instead of the right ones. Here is the complete code:
.h
#ifndef PERSON_H
#define PERSON_H
#include <iostream>
using namespace std;
class persona {
[Code] ......
I can't seem to figure out the algorithm to find the right permutation(s) of operands and operators.
We basically have a list of 6 unsigned integers. Using arithmetic operations (addition, subtraction, multiplication, division), find the arithmetic expression that evaluates to a target integer.
Example:
myIntegers = {3, 7, 8, 10, 50, 100};
trgtInt = 315;
Solution is (50 + 10) * 7 - 100 - 8 + 3
We also have the following conditions:
1) Each number from the list can be used only once, but does not have to be used. i.e an expression with 5 or less numbers is acceptable
2) Operators can be used multiple times
I am thinking a parenthesis-free notation like Polish or Reverse Polish notation should be used.
So this is the code I have so far which puts a bitmask seperator base on what I choose. My problem is when Im trying to do them in this manner.
1. 0 to 31, with minimum width set to 8, and separating between every 4 digits.
2. 2^0 to 2^16, with minimum width set to 17, separating between every 8 digits.
3. (2^0-1) to (2^16-1) with minimum width set to 16, and no seperation between digits.
I try doing number 2 called "String multyplyByTwo" but seems to be getting errors.
#include<iostream>
#include<string>
using namespace std;
string binToChar( const int n, unsigned minWidth = 8, unsigned sepMask = 0x11111110 ) {
[Code] ....
I believe I have the syntax correct but I'm having difficulty calling my overloaded == operator in main (last snip-it of code). Below are several files explaining the code.
Commission.h here is where the friend bool operator == exists and I believe I have it initialized correctly.
#ifndef COMMISSION_H_INCLUDED
#define COMMISSION_H_INCLUDED
using namespace std;
class Commission {
public:
Commission();
Commission(int, double, double, double );
~Commission();
[Code] .....
#include <iostream>
using namespace std;
int main(){
int polje[8][8];{
for(int i=0;i<8;i++)
for(int j=0;j<8;j++) {
[Code] .....
I don't get any errors,the program works. The problem is that it doesnt work how it should. This is a simple program that multiplies 2 variables(i and j)that go from 0 to 7. The problem I have is with the logical operators,i want the program to skip multiplication with 0 and when the 2 variables are the same value. When i try using only 1 logical operator it work.
I'm trying to overload an operator << so that it prints to a .txt file. Would these two codes basically do the same thing? If so, which one is the more efficient one to use?
ofstream& operator<<(ofstream& fout, const Grid& g);
ostream& operator<<(ostream & out, const Grid& g);
I have made a custom class matrices class which allows me to add, multiply, subtract (etc.) matrices. I have the following method for multiplication but I get an error that says
'invalid use of 'this' outside of a non-static member function'
How can I refer to the current instance without getting this error.
void operator *(Matrices& matrix2) {
this.multiplyMatrix(matrix2);
}