C++ :: How To Make Sure Dereference To Vector Is Valid
Oct 6, 2014
I have this piece of code in parts of my path finding algorithm
for( int head; head < q.size(); ++ head ){
walk& w = q[head];
// do manything with w
if( some_condition ) q.push_back( walk( w.x + 1, w.y, head ) );
}
However I notice that sometimes w is cannot be dereferenced. It can but it throws junk number at me. Perhaps the vector is changing it size and move the whole array to a different location. Is there anyway to make sure that w is always valid ?
I just want to use w because of shorter typing and cleaner look not because of performance. I also refrain from using macro.
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Jun 29, 2014
I get errors C2100 (illegal indirection) and C2088 ("<<": illegal for class) while trying to use the myPrint function (irrespectively of whether the set for printing contains pointers or not):
template <class T = std::string>
void myPrint(const std::set<T>& mySet) {
std::cout << "Size of vector is " << mySet.size() << ", Pointers: ";
bool pp = false; std::string str = "no";
[Code] ....
The errors point to the line "if (pp) { std::cout << *(*i) << ","; }", but I cannot figure out what's wrong with it...
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Feb 25, 2015
Code:
void dereference(int* a, int* b)
{
a=b;
}
int main(int argc, char **argv)
[Code] ....
Why isn't f and d the same after calling "dereference(f,d);"
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Apr 8, 2014
Why this code works
Elenco e1;
e1.add(Persona("a","b"));
e1.add(Persona("c","d"));
e1.add(Persona("e","f"));
e1.add(Persona("e","f"));
e1.remove(2); //list of 4 elements
but this not work?
Elenco e1;
e1.add(Persona("a","b"));
e1.add(Persona("c","d"));
e1.add(Persona("e","f"));
e1.remove(2); //list of 3 elements
This is remove method:
Persona Elenco:: remove(int pos){
list<Persona> ::iterator iter=l.begin();
for(int i=0 ;i<pos;i++){
iter++;
}
return *(l.erase(iter)); //erase ritorna un iterator
}
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Feb 8, 2014
I am trying to make a 5x3 2D-vector of integers, then set its i-capacity to be 5 and j-capacity to be 3, i.e:
vec2D[i][j] i = 1,2,3,4,5 j = 1,2,3
and then assign integer values to it.
#include <vector>
#include <iostream>
using namespace std;
int main () {
vector<vector<int> > vec2D;
[Code] ....
It compiles, but does not work properly:
Test.exe exited with code -1073741819
i-capacity before reserve: 0
i-capacity after reserve: 5
i = 0
j-capacity before reserve: 336043326
j-capacity after reserve: 336043326
i = 1
j-capacity before reserve: 4282929217
j-capacity after reserve: 4282929217
Press <RETURN> to close this window...
I am trying to convert a C code with dynamic 2D arrays, to a C++ code. I prefer to keep the vec2D[i][j] = ... way of assignment instead of using vec2D.push_back(...).
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Jun 8, 2013
let say
char temp[8][8];
and you want to make vector of this char
vector<????> boardVec;
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Mar 7, 2013
My program is a dictionary vector with a cin at the end that will read your input and check if it's in the dictionary.
#include "std_lib_facilities_3.h"
#include <algorithm>
#include <string>
#include <iostream>
string translate_to_lower(string s){
transform(s.begi[/code]n(), s[/code].end(), s.begin(), (int (*)(int)) tolower);
[Code] ...
How do I make the program accept inputs such as "hello?", "hello!", and "hello,"?
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Mar 9, 2014
I am supposed to make a scrabble game and randomize 10 of the letters.
Here's my code:
class Spinner
Spinner::Spinner(string things[], int numThings[], int n)
{
currentPosition = 0;
[Code].....
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Jul 28, 2013
My assignment is to write a system for managing a radio station. The code is composed of four classes:
Song: each song has a name, a composer and a singer, and has a few segments: INTRO,VERSE,CHORUS,TRANSITION, while each represents a different length string of chars.
Playlist: a multiset of songs, and a pointer to a RadioStatistics instance (see below).
RadioStation: a set of Songs (will represent the station database), and a list of Playlists, each playlist holds a few songs from the database.
RadioStatistics: can only be instantiate once, this object gather statistics; it has two maps: one that counts how many times a song was played, and second that counts how many times each singer was played. (the key is the song/singer name, and the value is the counter).
The RadioStation has a constant that defines a limit to how many times a song is allowed to be played. whenever a song reaches this limit (meaning, it was played too much), the program needs to skip to the next song in the database.
so, I run this test from main, and the program crashes (or more accuratly get stuck, since the console stays open and the program keeps working until I stop it).
I made a few changes and run the debugger a few times, and was able to focus on the problem.
Song.h:
Code:
#ifndef SONG_H_
#define SONG_H_
#include<iostream>
#include<string>
[Code] ....
I ran a step by step debugger, and found out the problem lays with line 90 in RadioManager.cpp, when the while loop runs its fourth iteration. It crashes when it tries to dereference the iterator, while it points to the fourth playlist in the list.
And here's some more weird stuff: when I comment out line 73 in main.cpp - it works perfectly fine! (line 73 in particular! commenting out any other line in main.cpp didn't worked around the bug!)
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Mar 11, 2013
I was asked by a friend about validity of following function prototypes,
void func1(int = 0, int*);
void func2(int = 1, int& = 2);
void func3(int*, int& = 3);
void func4(int& = 4, int* = 0);
void func5(int& = 0, int = 1);
void func6(int = 5, int& = 6, int* = 0);
I think the only prototype that is invalid is func1 because it does not have default parameter on the far right.
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Jan 31, 2014
I want to know if it's valid to use and/or when using the conditional operator.
Example:
value = textBox1.Text;
decimal? qty = (value.Equals("0") || value.Equals("0.0")) ? null : (decimal?)decimal.Parse(value);
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Jan 27, 2013
The following code writes to a file on either local disk to a remote disk (commented out code) on Windows 7 platform.
Code:
#include <iostream>
#include <fstream>
using namespace std;
int main () {
ofstream outfile;
[Code].....
The documentation does not specify what is a valid filename (path and filename). For example, will the "\server emp" path work on all operating systems to access a samba share? Does the constructor accept forward and backward slashes as folder separator on all operating systems?
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Mar 19, 2013
How can I write my simple program so if the user enters an invalid number, The program won’t exit? I know I am supposed to use a if (cin) or if (!cin),
But I don’t know where in the program or how I should use it. Right now my Program looks kind of like this:
If (number > 1 && number < 1001)
Go through some function loops
Else
Cout << “invalid number”;
I need to write it so when the user enters an invalid number, the program would Keep asking for the right number until it's given.
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Jul 13, 2013
Now I have to write a code which would determine whether an Email address is valid or not.
In my exercise a valid address should look like this : ___@___.___.il (___ for any letters)
E.g. Valid address:
something @ something . something . il Invalid: tami @ jce . ac . uk
(without spaces of course)
Code:
#include <iostream>
#include <string.h>
using namespace std;
int isValid (char s[]) {
int length=strlen(s), ind1=0, ind2=0;
[Code] ....
It doesn't work well. It says both addresses are wrong when the 1st one isn't.
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Sep 30, 2013
So my program is to check if a certain 9x9 sudoku grid is valid. i have to get the input through command argument. so for example.
./a.out sudoku.txt
So we have make my c program to use FILE I/O open and what not
program behavior must be as follow File does not exist.File contains something other than a sequence of 81 integers (too many, too few, non-int).
One or more of the values is not in the range 1..9 Violation of Sudoku rules (this is the big one!) In case 4, you should report the violation (or any one of the violations if there are multiple -- you do not need to exhaustively enumerate all violations).
For example: Row Violation: entries (2,2) and (2,6) are both equal to 7. (Similarly for column and box violations). All i know is that i need to make a 2d 9 by 9 array
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Jul 21, 2013
Is this a good way of writing this program?I wanted to start fresh with my new code though and a better title.Basically, I took what I learned from my questions in that thread and managed to build a list of musical notes( octaves, frequencies, sharp symbols, basically everything ).
Code:
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <math.h>
#define MAX_NOTES 88 /* 88 keys on a standard piano */
[code]...
I already know the frequencies are correct( they are rounded, but they should be close enough to the value ), but I wasn't so sure about the note labels. Obviously though, I'm not done with this program and I will be adding most of the functions Anduril suggested to take a text file and convert it into music. I just wanted to make sure I had everything correct before moving on. I probably didn't do the GetNextOctave() and GetNextNote() functions very efficiently so need suggestions on those functions also.
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Mar 20, 2013
Entering valid user input?
How can I write my simple program so if the user enters an invalid number, The program won’t exit? I know I am supposed to use a if (cin) or if (!cin), But I don’t know where in the program or how I should use it. Right now my Program looks kind of like this:
If (number > 1 && number < 1001)
Go through some function loops
Else
Cout << “invalid number”;
I need to write it so when the user enters an invalid number, the program Would Keep asking for the right number until it's given.
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May 2, 2014
#define PROJECT_ID ram
#define QUOTES(FILENAME) #FILENAME
#define DATA_VAR_FILENAME(PROJECT_ID) QUOTES(../##PROJECT_ID##_data_var.h)
#define DATA_VAR_FILE(PROJECT_ID) DATA_VAR_FILENAME(PROJECT_ID)
#define CUST_DATA_VAR_FILENAME DATA_VAR_FILE(PROJECT_ID)
When I tried to include CUST_DATA_VAR_FILENAME like below
#include CUST_DATA_VAR_FILENAME
Will get below error
error: pasting "/" and "ram" does not give a valid preprocessing token
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May 28, 2014
Is there a function in C/C++ that can check if a given 8-byte data block is a valid double value in the valid range?
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Mar 11, 2013
Why does the following line of code generate error as " pasting / and / doesn't generate a valid reprocessing token"?
Code:
#define comment /##/
int main() {
comment printf("hello");
return 0;
}
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May 12, 2013
if I include iostream twice in my project why is that valid? Wouldn't the linker see that there are two definitions of it and report a error, but it works?
By project I mean in multiple translation units.
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Oct 9, 2014
I have the below code, the first rich text box works fine but on the second i get the error
An unhandled exception of type 'System.ArgumentException' occurred in System.Windows.Forms.dll
Additional information: File format is not valid.
System.Windows.Forms.RichTextBox rtBox = new System.Windows.Forms.RichTextBox();
rtBox.Rtf = reader["Change_Description"] as string;
Change_Description = rtBox.Text;
System.Windows.Forms.RichTextBox rtBox2 = new System.Windows.Forms.RichTextBox();
rtBox2.Rtf = reader["Change_Justification"] as string;
Change_Justification = rtBox2.Text;
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Oct 10, 2014
C# type setting a char? I have tried setting as characters, as integers but nothing seems to work?
last try: char mchar = 'X'; // Character literal
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Jun 10, 2013
I am getting this error whenever I leave my drop down lists blank: "String was not recognized as a valid DateTime". My code is below:
aspx:
asp:DropDownList ID="cboDay" runat="server" Width="55px" Height="32px" AppendDataBoundItems="true">
<asp:ListItem></asp:ListItem></asp:DropDownList >
<asp:DropDownList ID="cboMonth" runat="server" Width="80px" Height="30px" AppendDataBoundItems="true">
[Code]....
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Dec 22, 2013
I just wonder whether 0xFFFF is a valid Unicode character.
When I using the following code:
CStringW strTempW;
CString strTemp1;
INT_PTR nLen;
strTempW.Format(L"%c", 0xFFFF);
nLen = strTempW.GetLength();
strTemp1 += strTempW;
nLen = strTemp1.GetLength();
After executing the first codeline strTempW.Format(L"%c", 0xFFFF), I will get strTempW of length 1, but cannot see it first character in Visual Studio watch window.
After executing the codelilne strTemp1 += strTempW, I will get strTemp1 of length 0.
Whether 0xFFFF is taken as a valid Unicode or not?
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Jul 13, 2013
I have to write a code which would determine either a URL address is correct or not.
Now, a valid address should look like: "www.something.something.uk".
It has to have 3 dots, 3 w-s in the beginning, and it must end with "uk".
E.g.
Valid addresses:
1. www.jce.ac.uk
2. www.tr2213.oi34.uk
Invalid addresses:
1. www2.jce.ac.uk
2. òæøéàìé - îëììä à÷ãîéú ìäðãñä éøåùìéí - ìéîåãé äðãñä ìúåàø øàùåï
3. www.something.uk
Just to be clear, this criteria mentioned above is not real, just homework
Code:
#include <iostream>
#include <string.h>
using namespace std;
int isValid (char s[])
{
int dots=0;
[Code] ......
It tells me both strings are incorrect but the first 1 is.
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