I 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){
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]
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 */
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 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?
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..
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.
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.
How does one use a functor as a static constexpr member? I had this basic functor for a class:
struct functor{ short operator()(char c)const{return c-'0';} };
And in the class, I use it as a static constexpr member: class Foo{ public: //... private: static constexpr functor k_funky = functor(); };
During the linking stage, I kept getting "undefined reference to 'Foo::k_funky'". So then I tried declaring the functor's constructor and operator function constexpr:
In C++ there are a number of primitives that are not defined in terms of other types. By this I'm thinking
int a = 1; char b = 'M'; float c = 3.45f; short d = 0xC3A3;
Is it possible to define your own literal? What I would like to do is have a hex literal for a data type where n = sizeof(data_type). If this type were a big integer, then I would want something like:
BigInt e = 0x13CA9B0C98D983E912DA0B0A9F87E0;
My goal is to assign a value from one contingous chunk of bytes and to not do it with a string.
these function works. but if i concat literal strings with '+', i must use '(string)'. so i'm trying overload the operator + for concat literal strings, but without sucess:(
"A constant, like a variable, is a memory location where a value can be stored. Unlike variables, constants never change in value. You must initialize a constant when it is created. C++ has two types of constants: literal and symbolic.
A literal constant is a value typed directly into your program wherever it is needed. For example, consider the following statement:
long width = 5
This statement assigns the integer variable width the value 5. The 5 in the statement is a literal constant. You can't assign a value to 5, and its value can't be changed.
The values true and false, which are stored in bool variables, also are literal constants.
A symbolic constant is a constant represented by a name, just like a variable. The const keyword precedes the type, name, and initialization. Here's a statement that sets the point reward for killing a zombie:
const int KILL_BONUS = 5000;
Whenever a zombie is dispatched, the player's score is increased by the reward:
playerScore = playerScore + KILL_BONUS;
If you decide later to increase the reward to 10,000 points, you can change the constant KILL_BONUS and it will be reflected throughout the program. If you were to use the literal constant 5000 instead, it would be more difficult to find all the places it is used and change the value. This reduces the potential for error."
what's the difference? Here is a program to demonstrate what I'm having trouble conceptualizing.
#include <iostream> using namespace std; int main() { int width = 10, length = 10; int area = width * length; cout << "Width: " << width << endl; cout << "Length: " << length << endl; cout << "Area: " << area << endl; return 0; }
Now, why would it be harder to go in and changed a regularly defined integer than one defined with the 'const' keyword proceeding it? For example, the width and length variables. My confusion comes from the point that they seem to both simply be variables with a value assigned to them. I feel as if the process of having to change a literal constant's value is synonymous to the process of having to change a symbolic constant's.
What shall I learn in order to send values from 0.00 to 5.00? I'm working with they Hitachi 16x2 LCD display.I've been sending/displaying literal values on it all day.
Code:
SendCharater(unsigned char val)
where the variable val corresponds to the LCD character table.I can also send Hello World to the display, like so:
Code:
void putsXLCD(unsigned char *buffer){ while(*buffer) // Write data to LCD up to null { while( BusyXLCD() ); // Wait while LCD is busy SendCharacter(*buffer); // Write character to LCD buffer++; // Increment buffer } return; }
I could type in putsXLCD("5.00") in order to display it on the LCD, but how do I implement this automatically for values, e.g. 0.00 to 5.00?It appears I can only pass literal values through the function SendCharacter, meaning that in order to display "0" I have to pass the value 0x30 (the hex value of "0" on the LCD Table).
My current thought process:Much like passing "Hello World" in the function putsXLCD(), I need to assign a pointer that points at each value in the "array" that I need to send. E.g., I need to send 3.24, so I need to point to "3", fetch the corresponding hex value in the LCD table, in this case 0x34, and the pass this 0x34 into the SendCharacter function, and so on. So, if this is the case, how can I fetch the corresponding hex value?
What is the efficiency of the two assignments (line 1 and 2), i.e. (function calls, number of copies made, etc), also the Big O notation. I know there are function calls for retrieving the size of each string in order to produce a new buffer for the concatenated string...any difference between line 1 and 2 in terms of efficiency?
String s("Hello"); String t("There"); 1. s = s + t; 2. s += t;
Ok, so I'm writing this code and when I build it keeps saying cannot implicitely convert type int to string even though I declared my variables as string. Why is it giving me this error?
private static string Repair() { string result=""; string beep; string spin; Console.WriteLine("Does your computer beep on startup?:(y,n)");
I would like to understand a function on strings. Below is a code that I took from my teacher where the user inputs a string and prints out the length of the string.
Code: #include <stdio.h> #include <string.h> int main() { char str[100]; int i = 0;
[Code] ....
Now I understand that it returns the count in "int" so my question is:
Let's say i declared
Code: int count = 0; at the beginning of the code and then made Code: count = strlen(str); why wouldn't i have the same result? Is there a way to do it also?
I have this string d ="3 J JD, K" and i want to split the string to individual string. I have this code which eliminates the comma but doesn't split the string into individual string.
#include <iostream> #include <string> #include <sstream> using namespace std; int main() { string str = "3 J JD,K"; stringstream ss(str);
[Code] ....
Output of the code is 3 J JD k
but I want 3 J JD K
Also after I split the string is there any way to put the split string into individual string variables.
I have problem with string compare. I want to compare the string user input with a string in binary. And I don't know how to do it. Problem in function login();Here is the code: And you also can download file in attachment too..
In this code, i declared a string constant and trying to print the length of string. I know that if i write char a1[7] or char a1[] than it runs and give aggregate output, but in this case it is giving double length of string.
I wrote a program that reads a list from a file and stores it in a string type vector. Now, I want the user to input a word so that the program can search the vector to see if that word already exists. I have used every possible way of reading input from the console and storing it in order to compare with the vector but it never results in a match. When I print the input string and the vector string they are exactly the same thing (or at least print to the console as if they were). I've tried using getline; using cin direct to a string var; using cin to a char array and then casting to string using string str(arr); I even added a newline at the end just in case and STILL I cannot get a match.
vector <string> currentSet; //read a list in from a file and has 9 items in it cin.ignore(); string line; getline(cin, line); if(line == vector[0]){//if printed to console line is HEAT and vector[0] is HEAT cout<<"match"<<endl; }
write a program that prompts the user to input a string and outputs the string in uppercase letters. (Use a character array to store the string.) Does this follow the criteria? This program is very similar to one I found on these forums but I have one problem, it outputs everything backwards! EX: dogs will output to SGOD. What I need to do to make it output correctly, I think it may have to do with getline?
#include <iostream> #include <cctype> #include <cstring> using namespace std; int main() { char let[100]; cout << "Enter what you would like to be UPPERCASE: ";
I made a simple little program that takes text from the clipboard, and spits out all the lines I've copied one at a time (so my program can analyze it).
everything works perfectly, except, it spits it own in the wrong order, I want it to spit out from bottom to top. but currently it spits out the data from top to bottom. here is my code :
Code: #include <iostream> #include <Windows.h> #include <string> #include <sstream> using namespace std; int main() { HANDLE clip; // assigns the var. clip to hold a handle ID.
[Code] .....
I want this loop to run backwards! Like it say's what I want to work backwards. Where as I know how to flip a while loop like this: while(x < 5), how to flip a loop like the one I'm using. how I can do this?
