I have been struggling with pointers. I am trying to write a program that first asks a user to input a filename. It then checks if the file exists and if it does it passes a pointer to the next function. The next function then asks the user for a specific word to look for and the function will search a text file for the word and do some other operations. My problem is that I do not understand how to use the pointer returned by my first function as an input to another function.
The following code has the first function file_check() and the second function word_search() which I think the way I am declaring it is the problem.
Background: I'm writing a convolutional encoder (and decoder, eventually) for a microprocessor (PIC24), for which I'm using structs and pointers to move from state to state. So far as I'm aware, everything I'm using in the PIC involves nothing other than ANSI C.
I have a little experience with structures, having written a linked-list program for a class a couple years back, but nothing since and never used structure arrays. I have the feeling I'm missing something basic here, which is what's so frustrating. The most confusing error (and I suspect the root of most of them) is the 'state undeclared', which I just can't figure.
The errors I'm getting are:
encoder.c:11: warning: 'struct memstate' declared inside parameter list encoder.c:11: warning: its scope is only this definition or declaration, which is probably not what you want encoder.c: In function 'state_init': encoder.c:22: error: two or more data types in declaration specifiers encoder.c:25: error: 'state' undeclared (first use in this function) encoder.c:25: error: (Each undeclared identifier is reported only once
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Code:
Code: //Includes #include <stdlib.h> //------------------------------------------------------------------------------ //Creates state machine and passes back pointer to 00 state void state_init(struct memstate* startpoint) { extern struct memstate { char output0; //output if next input is 0
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NB: I'm aware that at the moment, this code will do nothing except spin round that do-while loop. Once it's actually compiling I'll drop in some simple button-based test code so it'll check for the correct output.
I have a a group of text files that are used as input into a program. Another very similar program needs the same data in a different input format. I am writing a program that will read in each line of data and parse it. I have successfully written the program in main() such that it will read until the end of file. However, I am trying to re-write the program such that the algorithm is in an external function and will read one line at a time and then pass all of the character strings to the main program. The program will not compile and I am positive it has to do with an incorrect use of arrays in passing the variable "token". I am attaching a copy of the main program and the function.
forget everything from before. It came out of confusion regard the supplier functions. dis_s() and read_s() the part functions work and are not any different really.
when I run the dis_s() function it just prints out garbage until it segments. starts with a bunch of 0 and newlines until it starts printing locations on my computer...... it worked on campus with debian and I only copied it from gmail to my computer so I really don't understand whats up(im on mint).
I'm having some problems with a function. The function is supposed to find the two largest values in an array.
Code:
void find_two_largest( const int *a, int n, int *largest, int *second_largest){ largest = a; int temp; second_largest = a; for ( int i = 1; i < n; i++){ if (*(a + i) > *largest){ temp = *largest;
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I don't see any mistake with the code of the function, but when I try to call it inside my program it only returns 0 for both largest and second_largest.
Code:
int *find_middle( int *a, int n); void find_two_largest(const int *a, int n, int *largest, int *second_largest); int main() { int n;
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Do I have to declare the variables largest and second_largest as normal integer variables and then pass their addresses as arguments to find_largest or is that incorrect?
//This function takes the radius of a circle and returns the diameter, the circumference and the area. int circleStatistics(double radius, double *diameter, double *circumference, double *area);
//This function takes a number of days and returns how many years, weeks and remaining days that is. int convertTime(int days, int *y, int *w, int *d);
//This function takes a length of time and calculates the dilation of that time at a percentage of the speed of light. int lorentzTimeDilation(double normalTime, double percentC, double *dilatedTime);
I am writing a code that creates a deck of cards using a doubly linked list. One function, newDeck(), is made to create a new deck if the user wants. I don't have any problems creating the deck and it all seems to work fine, but when I run the whole program and a separate function needs to utilize the nodes in my deck, I get an error. Trying to find where there was a problem, I tried displaying the values of a card node in random parts of my code. At the end of the newDeck function, after the whole deck has been created, the card still displays correctly, yet when I return back to main immediately after newDeck has been called, I noticed that the values of my cards changed to either random values or they became null. I found this strange because in between the end of my newDeck function and at this point, there is no extra code so it doesn't seem as if there is any way the pointers could have been changed. Maybe It's because I don't have a complete understanding of pointers yet but is there any way that pointers can change values when returning from a function to main?
newDeck(head, tail, n); //this is how I call the function from main. void newDeck(Card* head, Card* tail, Card* n) //this is my function body { for (int i = 0; i < 4; i++) {
Code: void Class1::Func(shared_ptr<type1> parameter) { } or void Class1::Func(const shared_ptr<type1>& parameter) { } or Should I ever pass arguments/parameters to other objects using shared_ptr's or raw pointers?
I have this code where I am trying to retrieve the contents of the variable dev1 and dev2. for some reason when i compile and run I am getting 0 and 0.
i have a program that works, but now I am trying to get function1() to work. What it has to do is bring in the array and populate it with random letters. I don't know much about functions.
Code:
#include<stdio.h> #include<stdlib.h> #include<time.h> #define maxrow 20 //defines maxrow as a constant of 20 #define maxcol 30 //defines maxcol as a constant of 30 }
I think i am getting confused with passing structs and functions all in the same...When I run through the program (it compiles), the functions that add coins do not add, but rather just replace an old value with a new one.
#include <cstdlib> #include <iostream> using namespace std; struct coinbox {
I am trying to get some confirmation about how to pass to functions. If you want to assign default values to certain parameters, and have others defined inside the body of int main(), then the parameters which will have default values go at the end of the list. Is that correct?
i.e. The following code is wrong, because we cannot leave a black in the function call on the third line of the main function. However, if we switch the prototype to void Passing (int a, int c, int b = 1); and the function definition to void Passing (int a , int c, int b) everything will be okay and we can call the function as Passing (a, c).
In brief, we cannot do this EVER: Passing( a, , c)right? #include <iostream> using namespace std;
I've got a game engine with a line-trace collision method which returns the first object it hits. I'd like to be able to pass it a class-type so that it can ignore objects of other types.
consider this pseudo-code:
Entity* TraceEntity( const Vec3f& LineStart, const Vec3f& LineEnd, const Type atype ) { // check collision on entities, ignore entities of type 'atype'. // return whatever it finds }
I'd like to do this without template classes because it will result in a significant bloat in executable size every time I decided to trace for a new entity type (I've really developed a distaste for templates for this reason)
using type_info only checks for an object's deepest subclass, so it won't work for class C : public B : public A if I'm looking for classes of type B.
Now the book says to take the following program and add a member function to the CarType class which prints the values of all of its data members. Add two more data members which are relevant for cars. Add the use of these data members to the program (to the assignment statements for MyCar, to the operator prompt and input inside the getYourCar function, and to the print function you have created).
Here is my code. Whenever I run it, it takes my assigned variables in MyCar and prints those instead of the one which the user is inputting.
#include <iostream> #include <iomanip> #include <string> using namespace std; using namespace std; struct CarType { string maker;
the book I learn from gave a task to write a program which gets a matrix , and we have to write a function that switches 2 columns or rows the user inputs .as far as I know a function can not change variables in the main function without using pointers .so , theoretically, can a function described here can be written without using pointers ? as far as I tried - it can not.
I have a vector of pointers inside a seperate Exam class.
vector <Question* > question_list
The Question class is my base class in which I have derived sub classes for the different types of questions (MultipleChoice, LongAnswer, etc.). I am using my vector to hold the different types of questions.
in each of those classes I have virtual "write" functions in both the base and the derived classes, that write to a file differing for each type of question.
My problem now is calling the write function from a Exam function. I've tried several methods, such as:
for (size_t i = 0; i < question_list.size(); i++) { question_list[i].write(testfile.c_str()); }
but it comes with two errors: "error C2228:left of '.write' must have class/struct/union" along with "IntelliSense: expression must have class type"
I have made a write function for the exam class as well but am not sure what it should include since the Exam class is not a derived class of the Question class.
I am trying to pass input file between two functions. The code compiles but immediately upon running the program, there is a "bad cast" run time error.
My average is failing but I played and played with it and I still keep crashing.
Code: #include <iostream> using namespace std; void getScore(int score[], int NumGrades) { cout<<"How many grades do you need to enter?"<<endl; cin >> NumGrades; cout<<"Enter the Students Grade(s)"<<endl; for (int i=0; i<NumGrades; i++) { cin >> score[i];
At first i had my int variables in global scope however i cant do the so im trying to pass my variables from my main to the void functions but cant.....
