C++ :: Implicit Conversions To / From Library Type Only In Implementation
Apr 1, 2014
1. I designed two classes: Processor and Data.
2. Data represents some data object the user can pass to Processor's public methods.
3. Internally, Processor needs to use InternalData type which is based on the content of Data (I can use Data's public interface to get the required information from it, or construct a Data object using its public constructor when needed, and that's how I have done it so far).
4. To avoid repeating code and localize changes required when Data's interface would change someday, I made conversion functions from Data to InternalData and back inside Processor, as private methods.
Now here comes the kicker:
5. But I'd like these conversions to be implicit inside Processor's methods instead of explicit. And only there.
6. These conversion functions are only for Processor implementation's use. They shouldn't be visible nor accessible from the outside world.
Where the problem lays:
7. InternalData is a library type. I don't have control over it and I cannot modify its interface.
That is, I cannot just add converting constructors or conversion operator member functions to them.You can consider it to be built-in type if you wish.
8. I don't want to put those converters inside Data class either, since it's not its business and it shouldn't know that Processor converts it to something else internally.
Long story short, I'd like to teach the Processor's implementation how to make type conversions between Data and InternalData implicitly, but no one else except Processor should be affected by it. Outside world shouldn't be able to do these conversions or even know about them being done inside Processor's implementation.Is there any way to do it in C++?
The core of the problem seems to be the fact that in C++ defining implicit conversions is possible only from/to a user-defined type when defining this type. I don't know of any way to define such conversions for some other type's internal use only. (Especially when I don't have control about one of these converted types.)
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 have a class "Result" with a single template function Set(const std::string& arName, T& val) and a specialization of this function Set<Real>(const std::string& arName, Real& val) where Real is a typedef for double. The class is in a shared library and I use it in my main program. If I do result->Set<GLOBAL::Real>("U", 100.0); the wrong template function is called!
I check this by the output with std::cout.
Maybe it's a problem with the typedef.
If I link the object file of the Result class directly to my main program (no shared library), it works.
I realize that implicit int rule was removed in C99 but gcc still takes this approach by default. I wonder why this happens:
bbb = 5; // legal int main(void) { aaa = 10; // illegal auto aaa = 10 // legal
Inside function a specifier is needed. Error message with no specifier used is:
error: ‘aaa’ undeclared (first use in this function)
Is this because of linkage - bbb variable has an external linkage so compiler knows that we are defining a variable here while inside mean() we need to show compiler that aaa is defined right here, it does not come from external functions?
I got the following to compile and execute, but I don't understand how this works. Here is the code verbatim:
Code: // Basic conversions in C #include <stdio.h> int main () { float f1 = 123.125, f2; int i1, i2 = -150; char c = 'a';
[Code] .....
Okay, so first we have some variables declared as integers, floats, (and that char what it's doing). On the same lines we have values assigned to some of those variables. At first the "f2" and the "i1" confused me, but I think they're just variables whose type has been declared but have not received a value. So far I think I'm good. Then we get into the routines
I think I understand the first one. i1 didn't originally receive a value assigned to it, so when it says f1 = i1, then f1 (123.125) just becomes an integer, simple enough.
Then we get to the next routine and I'm like what dafuq??? So first we have f1 (123.125) being set to i2 (-150). wtf? So does that mean f1 is now going to have the value of -150? Vice versa? How are they becoming equal? Or does it have nothing to do with the values of the variables at all and just the type??? I'm just totally lost.
The output of that line is "-150 assigned to a float produces -150.000000." Which makes perfect sense to me written in plain English, but I don't understand how the C code works ....
I have a project assignment for school to write a program that does number conversions using bitwise operators. The premise is that the user enters a number with one of three letter prefixes -- Q1232, O6322, H762FA, etc. -- and the program will take that number and convert it to the other two number bases. Q is for quarternary, O is for octal, and H is for hexadecimal. The transformations should be done using bitwise operators and bit shifting. I am guessing I need to scan the number, convert it to binary, then convert it to the other two bases.
However, I am completely new to bitwise operators and bit shifting, so how to convert numbers of different bases to binary and then binary to other bases using these bit and bitwise functions. I don't have much code done yet, since I am still unsure of how to approach it, but I'll post what little I have.
Here it is:
#include <stdio.h> #include <string.h> int main() { char numType; printf(" The user will enter a number up to 32 digits in quarternary "); printf("(base 4), octal (base 8), or hexadecimal (base 16). If in ");
[Code] ....
I figure in each case I can write a function that converts the entered number to binary, then maybe two more functions that convert said binary number to the other bases. For default in the switch I will tell the user they entered an invalid number. I don't have the program looping until the user types 'EXIT' yet, but I will once I figure out anything about these bitwise operators.
So, in my platform, conversion from an unsigend integer primitive data type to any bigger integer primitive data type never extends the most significant bit of the former integer and conversion from an signed integer primitive data type to any bigger integer primitive data type always extends the most significant bit of the former integer. This is convenient to mantain the same value when converting between integer primitive data types of the same signedness (i.e, signed integers or unsigned integers).
Write a program that creates and displays a table of temperature conversions. Get the starting temperature from the keyboard in degrees Celsius (do not allow input of a value below absolute zero). Also get an integer value to represent the number of degrees to increment for each of a 20 row table (do not allow the increment value to be less than one. The first column will be a row number starting with one, follow by the Celsius value and then the conversions into Fahrenheit, Kelvin, and Rankine. Be sure that all columns are neatly right aligned for a variety of inputs.
Thats what i wrote so far:
#include <iostream> #include <iomanip> using namespace std; int main() { double C,F,K,R,n,a; cout <<"Enter starting temperature in Celsius: "; cin >> C; [Code] ....
Thats what the instructor looking for:
Enter starting temperature in Celsius: -500 ERROR: Temp must be >= -273.15: -273.15 Enter increments in degrees Celsius: 100
run-time check failure #0 - the value of ESP was not properly saved across a function call. This is usually a result of calling a function declared with one calling convention with a function pointer declared with a different calling convention
when i try to run my code. It has compiled fine on another computer, but it simply will not work on this one. This is the part of code where it is receiving the error. it has to do with the stoi
Code: #include <string> // for use of string #include <fstream> //for file handling #include <iostream> // for file handling #include <cstdlib> #include <iomanip> //for the setprecision used further below using namespace std; struct MasterData //struct created named 'MasterData' to hold one line from master file
I've been reading about libraries; How to make them, how to use them, the different types of libraries, etc..
When using a shared library, does the program require that library to be installed on the computer after the program has been compiled into an .exe?
Ie.. if somebody downloaded a "Helloworld.exe" that I had compiled on my computer using a shared library (that wasn't part of a standard operating system), would they also need that shared library on their computer for the program to run without errors?
and for Static Libraries, when I compile a program using a static library, does it include in the final binary only the functions of the library that are actually used, or does the compiler add in the entire library?
I'm having some problems with changing an array of numbers of type char to type int. Every time i try to sum 2 array indexed values it returns some letter or symbol. Also, if i change the type of the array in the functions the compiler gives me an error message. I would also like to add that the problem requires that the first two arrays be char so each individual number gets assigned to a different value.
My current code is:
Code: #include <iostream> void input(char a[], char b[], int& size_a, int& size_b); void convert(char a[], int size); void reverse(char a[], int size); void add(char a[], char b[], int c[], int size); int main()
list contains, in order: A, B and C in any order, D, E
I am thinking it is possible with some clever template and polymorphism combos, but maybe not. As a last resort I know how to make it work by storing static type information in each class, but I'd like to avoid that if possible.
I have to develop minimalistic implementation of RSA algorithm in C for an embedded device.
I'm doing that for two days but I have run into a problem. The N modulus is the limitation for the maximum message value to be encrypted with RSA.
For example theoretically RSA-1024 can encrypt/decrypt messages 1024 bits long but I still cannot understand how to choose p and q values to produce N == pow(2, 1024).
Is it possible to encrypt/decrypt 1024 bits long messages in practice if the N < pow(2, 1024)?
I was trying to implement Big Integer Implementation. I wanted to start with the basic operation of addition. I am having some problems with operator overloading part
I was looking at this tutorial: [URL] ..... And I was wondering if implementing it in MVC would be pretty much the same way? How would I display feed items in the views page using?
I tried something like:
ReaderModel Reader = new ReaderModel(); Collection<Rss.Item> List; List = Reader.GetFeed(); ViewData["RssItems"] = List;
// then in index.cshtml @foreach(Collection<Rss.Item> items in ViewData["RssItems"]) { <h3>items.Title</h3> ... }
I don't think this is right as I'm getting those red error lines...
I've been working on creating a simulator to crash two galaxies together as part of a project to stress test a CUDA super computer. I've got a long way to go and am currently just working on correctly simulating n-body gravity functions. First I will use this to simulate the cores of the galaxies (the black holes) and eventually the stars.
So long story short I'm working on the beginnings of a gravity simulator. At this point I found some basic code that works well but doesn't quite give the effect I'm looking for.
The code below only pulls each object towards each other like a spring faster and faster until they shoot off into infinity. I try to give one of my bodies an initial velocity to get it to orbit another, but it always just shoots straight at the other body. I'm thinking I need to factor in inertia so that the initial velocity doesn't just get calculated away really fast by the other calculations.
I'm really looking for a bit of direction to get a real gravity simulator with orbits and such working right so eventually I can scale it up to a galaxy, throw in 100B stars and let the CUDA run for a month..
As you can see, I'm calculating all the bodies in a vector called "galaxies" with each other, and doing a basic gravity calculation to it. The update_position function simply takes the calculated acceleration and uses it to calculate the velocity and position based on the "elapsedTime".
I think I need to use the Varlet or Runge-Kutta integration methods, after doing a bit more research.
Output to terminal: 0 2 3 1 4 5 but it should be: 0 2 4 5 3 1
Here's my code:
#include<stdio.h> #include<assert.h> /* maxVertices represents maximum number of vertices that can be present in the graph. */ #define maxVertices 100 void Dfs(int graph[][maxVertices], int *size, int presentVertex,int *visited)
I am trying to implement a stack class which has struct data type as its private member. I am getiing the following error ,
bash-3.2$ g++ stack_str_arr.cpp stack_str_arr.cpp: In member function ‘void stack::push(int)’: stack_str_arr.cpp:39: error: ‘top’ was not declared in this scope stack_str_arr.cpp: At global scope: stack_str_arr.cpp:43: error: no ‘void stack::display()’ member function declared in class ‘stack’
Code:
#include<iostream> using namespace std; #define MAX 5 class stack { public : stack();
I'm implementing a 4x4 matrix class and all is going well until the inverse function turned up. I'm trying to implement the inverse function, but I can't seem to get my head around it.
I've tried the internet, but found nothing useful. Also, I've looked into source code of other programs/libraries that implement a matrix class, but the code is unreadable.
How I can implement this damn 4x4 inverse function? I know the process of inversion, but putting that process into code is proving quite a challenge.
In addition, I do have some code, but it's unmanageable and inefficient at the moment. If you want to see it, just ask.
Additional question(s): What applications does the inverse matrix have in 3-D?
