In the following char array, notice the use of a backspace character in a string literal: ''.
char text1[50] = "aHello,
World! Mistakee was "Extra 'e'"!
";
What exactly does a backspace character do here? When the compiler evaluates this line, does it actually delete the previous character, like when you press the backspace button on the keyboard?
How to avoid using Backspace character with push_back? I'm making a software as an ATM, so when the user try to enter the password the user only sees *******, but when trying to delete it doesn't delete a character. It just adds a new one. Here's my code:
string password2 = "";
cout << "PASSWORD: ";
ch = _getch();
while(ch != 13) //character 13 is enter {
password2.push_back(ch);
cout << '*';
ch = _getch();
}
And also, I try to use pop_back(); but it doesn't work either.
Very new to programming, and I know that there must be another way on inputting a string into each array cells not by just inputting it one by one, but as a whole. My code at the meantime is: [URL]
View 1 Replies View RelatedI have a binary identifier which I tried to make a constexpr since all of its calculations would never occur during runtime (this is true for literal identifiers, right?). Since constant expressions can only have one instruction, I tried to cheat a little and returned an immediate call to a lambda function. This failed miserably however. I tried making a constexpr function pointer and called that from _binary down below, but the compiler still felt that it wasn't a constexpr. Why is this? And is there a way to make a function like _b below constexpr?
#include <iostream>
#include <cstddef>
using std::cout;
using std::endl;
long unsigned //Original
operator"" _b(const char* const literal, size_t lsize){
[Code] .....
In another forum, this example code fragment was stated as being an example of undefined behavior. My understanding is that a literal string exists from program start to program termination, so I don't see the issue, even though the literal string is probably in a different part of memory.
Code: /* ... */
const char *pstr = "example";
/* or even */
char *pstr = "example";
/* as long as no attempt is made to modify the data pointed to by pstr, */
/* unless pstr is later changed to point to a stack or heap based string */
This compiles o.k.:
Code:
int main(void){
char *a;
a = (char*) malloc (100*sizeof(char));
[Code]....
I get an error saying "pointer being freed was not allocated". This happens for free(a), free(*a), free(&a), free(&*a).
So if I no longer need "1234567"... how do I get rid of this memory element?
how string literal that works with the cin object?
char * str = "This is a string constant";
Is the str stored the address of the first character of the string literal?
But some books just state that the pointer-to-char (char pointer) stores the address of the string literal". So just wonder how it is.
When it is used with cout, cout just treats it like a string and instead of printing the address, it just prints out all characters one by one until it reaches the terminated null character.
If this is the case, then I am just wondering how cin works with it? with a statement like this cin >> str; ?
Does the computer allocate enough memory for it? and then cin stores the first character into the first address and then advances to the next address and stores the next character?
I have a struct like this:
Code:
struct String{
char* data;
std::size_t size;
};
I would like to be able to create const variables of this type for string literals.
Code:
const String message;
Is there an elegant way to create a const String like this when data is a string literal?
I tried this:
Code:
const char *string_data = "Hello";
size_t string_size = strlen(string_data) + 1;
const String string = {string_data, string_size};
The problem with that is that string.data isn't considered const during the initialization of the String struct so the compiler throws an error. It doesn't feel very elegant to do it like this either way.
Is there an elegant solution to this problem? I would like to avoid making a copy of the string literal.
I'm making a .json loader for a project that I'm working on, and to simplify things, I decided to make all the root attributes named in a separate file. Here's my problem: my loading function, Add(const char* id), works just fine when I pass it a string literal.
However, when I use a function that iterates through a vector list, even with the exact same definitions as the literal, it returns the error: std::out_of_range at memory location 0x0026fb30
I've stepped through it with the VS2010 debugger about a hundred times, checked against memory locations, and just have done everything I can think of, all to no avail..
The code, with data-checking omitted:
The std::map I'm adding to:
static std::map<const char*, Item*> *s_mItems;
Initialized as std::map<const char*, Item*> *Item::s_mItems;
Add() Function (Works by itself with a literal):
static bool Add(const char* id) {
...
std::string name = node.Get("name").ToString();
std::string desc = node.Get("description").ToString();
int rarity = StrToRarity(node.Get("rarity").ToString());
[Code] ....
AddList() function, where the program always breaks:
static void AddList(std::vector<std::string> list) {
for(std::vector<std::string>::iterator it = list.begin(); it != list.end(); it++) {
Add(it->c_str());
}
}
Background: I'm using SDL and CodeBlocks and trying to make a Graphics class that would simplify some SDL operations such as drawing and loading images.
Issue: The loadImage function in the graphics class fails to load the image correctly and so the program prints out a blank window during run-time. I've tried multiple ways of passing a string literal into the function the surface temp fails to load and so background in Game fails to load. After testing it several times, I'm pretty sure that the issue lies with SDL_LoadBMP not registering the passed variable for whatever reason. I know the image is in the right place as writing SDL_LoadBMP("./Graphics/image.bmp"); brings it up just fine.
Current Code:
Main simply creates a Game object and execute(), so I didn't feel the need to put it on here.
Game.h
#ifndef GAME_H
#define GAME_H
#include "SDL/SDL.h"
#include "SDL/SDL_ttf.h"
#include "Graphics.h"
#include <string>
#include <cstring>
using namespace std;
//GLOBAL CONSTANTS
//game window settings
[Code] ....
Output: A blank window. (It should show the background image but doesn't.)
Note: I originally wrote it as gfx.loadImage(background, "./Graphics/image.bmp") but that gives me a conversion warning and still fails to show the image when the program runs. I've tried looking up examples similar to what I was doing but no one else seems to have this problem.
So I'm trying to create a function that replaces any instance of a character in a string with another. So first I tried the replace() string member function:
In my implementation file
void NewString::ReplaceChar(const char& target,const char& entry)
{
this->replace(this->begin(),this->end(), target, entry);
};
Main program
#include "NewString.h"
using namespace ...;
int main()
[Code].....
Instead of replacing the the l's with y's it outputted a long string of y's. Also, NewString is derived from the string class (it's for the assignment). the header and whole implementation file, already tested.
I've also tried, instead, to use a for loop in ReplaceChar() but I need to overload the == operator and I don't know how I should exactly:
bool NewString::operator ==(const char& target)const {
if(*this == target)
return true;
[Code]....
I want the == operator to test if the value in the char array is equal to target but I'm not sure how to pass in the position. I'm guessing the this pointer in ReplaceChar() is not the same as the one dereferenced in ==() because target is never replaced by entry in the string.
[URL]
#include <iostream>
#include <string>
#include <conio.h>
[Code].....
the code use in above link is good but one problem i cant able to use backspace to remove mistake if user made any mistake he cant able to remove the mistaken character
I'm making a calculator project but i can't find a solution for backspace button ,, i used these code -->
TxtNumber.Text.Remove(0,1);
But it removed the first number i wrote in the TxtNumber(TextBox) not the last one !!!!
how work backspace key in c++.i want to make a program which can work as a backspace number
View 1 Replies View RelatedI'm trying to get the int value of each character in a string and then add them all together so I can do a 1's complement of the total value. I'm trying to do simple checkum kinda of thing for verification of data.
For example: string DPacket = "Hello World!";
I would like to have each character added and do the ones complement. Will it be easier to convert first to int and then add or any other easier way? So my result should be the decimal value addition of each character and then do the ones complement to that.
I know how to remove certain characters from a string by using something like this:
Code: string str ("Hello world!");
erase (0, 6);
That's great if I want to do that manually, but say if someone entered a string, how would I automatically remove every other character they entered?
I want to check whether a certain character is in a string or not but my code is not working
Code:
#include<stdio.h>
#include<string.h>
int main()
{
[Code].....
Let's say i have a string "file.txt" and i want to insert "_out" to make it look like "file_out.txt"
I don't know how to do this ....
Copy some characters from char * arg to char * first using a loop with specific conditions.
Code:
char * arg;
// set arg some string...
char first_[25];
char * first;
int length;
length=strlen(arg);
for (n++; arg[n] != '}' || n>=length-1; n++)
strcpy(first,arg[n]); // first += arg[n]; I have strcpy(first,arg[n]); but arg[n] is char and strcpy expects char * ;
how to solve this?
It's been about two years since I last program c, now I need to do it for a basic project. How would I print out one letter in a string?
For example lets say I have a string called str=[Hello]. I want to display the third letter so just the "l". Here's what I have so far:
Code:
#include<stdio.h>
int main() {
char str[50] = "Hello";
printf("The third letter is : %s
",str[3]);
return 0;
}
I'm trying to find a < character in a document, get it's position. Then find > and get it's position. Then i want to delete all things between that but runtime is terminating my process so i don't know what to do.
The code:
#include <iostream>
#include <conio.h>
#include <stdio.h>
[Code].....
I want to input a string, say: abcdaa so, the program should output:
a
b
c
d
In other words, the program will display each character for only ONCE!!!! And display their frequency. Here is my idea: user will input a string and such string will be copied into another string variable called "checker".There will be a loop and each character will be printed, BUT, first, the program will check if the character to be printed is not equals to all elements of the checker string.
I already have the function to count the frequency of each character
GOAL: to make a program that will accept a string and use the HUFFMAN CODING to compress it.
for(x=0; x<string_in.size(); x++) {
cout<<" "<<string_in[x]<<endl;
for(y=0; y<string_in.size(); y++) {
if(checker[y]==string_in[x])
break;
else
checker[x]=string_in[x];
}
}
I have an open file dialog that opend the xml file and store the path to the textbox, it returns the path correctly but when i need to store that xml file into the database it tells me that there is an error next to '' because when i try to debug it it gives me "C:\Student Results\FC2015.xml" this results then it breaks. here is my code:
This code returns xml path to textbox
OpenFileDialog ofd = new OpenFileDialog();
ofd.Filter = "XML Files (*.xml)|*.xml";
ofd.FilterIndex = 0;
[Code]....
I need to make a function that removes a function in a c-string. This is what I have:
#include <iostream>
using namespace std;
char removeCharacter (char *str, char c)
{
[Code].....
I keep getting this error after I input:
Code:
Unhandled exception at 0x54AE350B (msvcp110d.dll) in Random.exe: 0xC0000005: Access violation writing location 0x0131CA21.
Code:
#include <iostream>
#include <cstring>
//Prototypes
void lastChar(char *);
int main() {
const int LENGTH = 21;
[Code] ....
It builds without any errors. I am just trying to output the last character in the C-string. Am I doing this all wrong?
I wish to convert a character directly to a string for a top-secret project I'm working on. It needs to be portable across various machines with different sized Indians.
Code:
#include <stdio.h>
int main(void)
{
const int i = 0x0041;
const char *str_p = (char *) &i;
}
[code]....
I want this to output an 'A', but I'm not sure this code will work on my friend's mom's S/360.