What the second print statement prints
main() {
struct s1{
char *str;
int i;
struct s1 *ptr;
[Code] .....
I executed the code and the output was some number(for second printf) but it should print a string.
I have an assignment where I need to use pointers to do a few things and I am a little confused on the syntax of it all. My question is how do you use a pointer to point to an array of structs.
For example
struct info{
char firstName[15];
char lastName[15];
};
main() {
info person[4];
cout << "The third letter of the second persons first name is: "; // ?????
}
how would I define a pointer to point to the third letter of first name the second person in the "person" array.
I have a struct and I want to implement in with pointers and functions.
What is the corect syntax? For example:
Code:
typedef struct XYZ
{
int x;
int y;
int z;
}XYZ_t;
int func( using the XYZ_t struct)
[Code] .....
I have this struct declaration to create a linked list
struct node {
string y;
node* next;
};
If I create a linked list of 3 nodes
A->B->C->NULL
A->y is "a"
B->y is "b"
C->y is "c"
Since they are consecutive in memory. How far apart are the strings in memory?
I tried doing something like
int n = &(head->next->x)-&(head->x);
The problem is that I got 6 while debugging and 2 otherwise.
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
[Code]....
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
[code]...
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 am having a lot of trouble being able to get data from a file and input it into given structs and arrays of structs and then outputting the file. We are given a file that contains 96 lines and looks like this:
Arzin, Neil
2.3 6.0 5.0 6.7 7.8 5.6 8.9 7.6
Babbage, Charles
2.3 5.6 6.5 7.6 8.7 7.8 5.4 4.5
This file continues for 24 different people and then repeats with different scores (the second line).
The first number, in this case is 2.3 for both people is a difficulty rating. The next 6 numbers are scores.
We are given this data in order to set up our structs and arrays and my code:
#include <iostream>
#include <fstream>
#include <iomanip>
#include <string>
#include <cmath>
using namespace std;
int main () {
ifstream inFile;
inFile.open("C://diveData.txt);
[Code] .....
I'm trying to create an array of pointers to pointers which will point to array of pointers (to strings) I tried
Code:
int i;
char *string[]={
"my name is dave",
"we like to dance together",
"sunny day",
"hello",
[code]...
the app keeps crashing , I don't know how to make the array-elements to point to another array-elements..
I am a little confused while comparing char pointers to integer pointers. Here is the problem:
Consider the following statement;
char *ptr = "Hello";
char cArr[] = "Hello";
When I do cout << ptr; it prints Hello, same is the case with the statement
cout << cArr;
As ptr and cArr are pointers, they should print addresses rather than contents, but if I have an interger array i.e.
int iArr[] = {1, 2, 3};
If I cout << iArr; it displays the expected result(i.e. prints address) but pointers to character array while outputting doesn't show the address but shows the contents, Why??
If i want to input (FROM A FUNCTION) information into a struct:
* How do I define/ call/ prototype that function.
* How do I check if that array inside the function is empty?
I'm working on a project involving nested classes and structs like this:
Code: class A {
public:class B {
public:f()
{A::C* iCanDoThis; //no errors.
iCanAlsoDoThis->root->.... //this also works fine.}private:A::C* iCannotDoThis //this is what I would like to do.
Has errors
A* iCanAlsoDoThis;};private:struct C
{..data..};
C* root;};
Is it possible make a pointer to struct C a private member of class B?
The main is not working properly, I get strange missing parenthesis notices and array errors which I am not understanding. How to identify the errors. Functions are included.
Code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int menu ();
double change_value (double * value);
[Code] ......
I'm currently working on a program that writes an array of struct to a file and then read back the data from the file to another array of struct. At the bottom is an image of my result.
My goal is to end up with two identical struct arrays but my program fails to do this. My struct have to members: ID and kind (of animals in this case). I declare my first arraystruct africa[] with "monkey" and "giraffe" with their respectively IDnr: 112 and 555. I stream this data to a file and read read them back to the arraystruct get_animal[]. Simply I want the get_animal[] to be identical with the africa[] when the program is over, but that is not so. According to my result(bottom image) it display:
112, monkey (get_animal[0])
112, monkey (get_animal[1])
meaning that get_animal[0] is identical to africa[0] get_animal[1] is also identical to africa[0]
but why? I want get_animal[1] to be identical with africa[1]. meaning I want the result to look like this:
112, monkey
555, giraffe
I've also made the program to print the parameters of my fwrite/fread calls. Why is the 3rd parameter = 1 meaning that only 1 element will be read/written when my program just read/write 2 elements?
Code:
main(){
FILE *fp;
struct animals
{
int id;
char kind[20];
} africa[1] = {{112,"monkey"}, {555,"giraffe"}};
}
[code]....
How would I be able to have this display the rest of the households without having to have 13 separate cout lines(one for each household)? In other words, how can I set it up to increment the output?
#include <iostream>
#include <iomanip>
#include <string>
using namespace std;
struct Household {
int idNumber;
int income;
[Code] ....
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 {
[code].....
I can't seem to remember everything I should about constructors. I'm looking for a way to create an array of structs, using a constructor. My code should explain.
struct myStruct
{
private:
int structInt1, structInt2;
[Code].....
What I'm trying to do :
struct foo {int x; int y;};
foo function_example(int x, int y) {
foo temp;
temp.x = x;
temp.y = y;
return temp;
}
Works as is, however when I try doing it through seperate class files :
//header file for class example_class
struct foo {int x; int y;};
foo function_example(int x, int y);
//source file for example_class
foo example_class::function_example(int x, int y) {
foo temp;
temp.x = x;
temp.y = y;
return temp;
}
I get an error telling me that foo is undefined, and that declaration of function_example(int x, int y) is incompatible with the declaration of it in the header file.
How to fill a vector with structs that are read in from a separate file. Each line in the file would read for example "Doe John M 26" for the name of the person, gender and age. I just need to get pointed in the right direction so I can get this started.
View 2 Replies View RelatedWhat is the difference between reading from binary file between the following way:
struct aStrct{
int number;
}vars[];
while(file.good())
file.read((char*)&vars, sizeof(aStrct))
And
while(file.good())
file.read((char*)&vars[i], sizeof(aStrct))
i++;
Write a program for the following problem. You're given a file that contains a collection if IDs and scores (type int) for an exam in your computer course. You're to compute the average of these scores and assign grades to each student according to the following rule:
If a student's score is within 10 points (above or below) of the average, assign a grade of satisfactory. If a studnt's score is more than 10 points above average, assign a grade of outstanding. If a student's score is more than 10 points below average, assign a grade of unsatisfactory.
The output from your program should consist of a labeled three-column list that shows each ID, score, and corresponding grade. Use a struct to store each student's data and an array of structs to store the whole class. The struct should have a data member for id, score, and grade.
I was given the following file grades:
3313904258647075100
568888487970797094
4700504489737073100
956188698887846398
31999669100908867100
376878578059571560
82917256708274983
7754766293100784158
81469468999493954
2106984796947027100
So far, I have this much, but the output is all wrong. I also haven't tackled the grade part yet.
Code:
//grader.cpp
//Grades
#include <fstream>//required for file streams
#include <iostream>//input/output
#include <cstdlib>//for definition of EXIT_FAILURE
#include <string>
#include <iomanip>
using namespace std;
#define inFileGrades "grades.txt"//grades
[code]....
I am versed in qsorting struct members within a struct instance, as in the example below:
Code:
#include <iostream>
#include <stdlib.h>
using namespace std;
struct item_database {
[Code]....
What I CANT do however is to sort an array of structs by one of its members. This is a complete different problem even if it sounds similar.
In other words, the problem is this; Say we have a struct:
Code:
struct item_database {
int key;
string token;
};
Then we declare an array of this struct in the heap:
Code: item_database *idptr = new item_database[700000]; and initialize its values.
How would one go about sorting this heap array of structs by its member function "token"?
I used the following call to qsort (standard library) and call to the compare function but it doesnt work:
Code:
qsort (idptr, 1000, sizeof(string), compare);
Code: int compare (const void* a, const void* b){
if (*(char*)a >= *(char*)b)
return 1;
else
return -1;
}
Or in more lamens terms say we have the following stuct instances:
Key: Token:
1 Hello
2 World
3 How
4 Are
5 You
Then I need those structs to order according to token (alphabetically, increasing or decreasing depending whats in our compare function).....
what I am trying to do is to pass to a function the address of an array of structs, so I can later modify the items within the struct, within the array
Code:
typedef struct { //A struct of name auctionint bidder;float bid;} auction;
void myFunction (auction * auctionItem[]){(*aucItem[x]).bid = y;(*aucItem[x]).bidder = z;}
int main(){auction theItems[10];
myFunction(theItems);} Where x, y, and z can be any number.
When I try to run my code the IDE (I'm using Code::Blocks 12.11) does not give me any errors, but it does give me a warning:
warning: passing argument 3 of '<function name>' from incompatible pointer type [enabled by default]
and the note:
note: expected 'struct <struct name> **' but argument is of type 'struct <struct name> *'.Also, when I run the program, it will crash and return garbage.
I have a structure product_array *pa that contains a pointer *arr to an array of structs and count that adds 1 when a new product is added (set to NULL initially). I have to write a function which adds a new product entry to that array. One product entry has *title, *code, stock and price parameters. The array is dynamically allocated and I’m supposed to:
1. Reallocate space for array.
2. Update product_array.
3. Initialize it.
Also, code should be truncated to 7 characters.Products can be added multiple times, so the initial size is unknown.
Code:
void add_product(struct product_array *pa, const char *title, const char *code, int stock, double price)
{
for (int i = 0 ;; i++){
pa->arr = realloc(pa->arr, sizeof(struct product_array));
[code]....
How do I set all of these string and double value(s) to 0?
Code:
#define MAXcharacters 12
#define MAXaccounts 100
struct Records {
char userid[MAXcharacters + 1];
char password[MAXcharacters + 1];
double balance;
};
[code]...
I have a deck of 108 cards inside a 2D array and want to deal these card by 7 to 4 player. Each player had a id. The player and id are stored in a file while i've read in array each. Now I have to deal the cards.
Code:
struct card{
char color;
int rank;
char action[24];
char location[108]; Code: struct players{char name[10];
int id[5];
char hand;
};
I need to create a dynamically allocated, growable, queue of structs. I tried my best to do as much as I could. What's holding me up is the queue aspect of it.
#include <iostream>
#include <string>
#include <stdlib.h>
[Code].....
I need to scan a .csv file that contains the following info:
programming,03,60,141,01,W,2015
programming,03,60,141,30,W,2015
Algebra,03,62,102,02,S,2013
Religion,08,98,938,20,F,2014
So i made a struct:
typedef struct CourseInfo {
int courseID;
char courseName[50];
char courseCode[13];
char term[7];
} courseinfo;
Where course code is the 4 numbers after the name together and the term is the letter and year in the last two pieces of info. I got this to work:
int main() {
FILE *p;
p = fopen("input.csv", "r+");
if(p == NULL) {
puts("The file could not be opened");
[Code] ......
But lets say i dont know how many lines i have in my file and i want to count them and then use that size for my array so i tried this by:
int main() {
FILE *p;
int lines = 1;
char ch;
p = fopen("input.csv", "r+");
if(p == NULL) {
[Code] .....
But the second program is not working for unknown reasons. I do not get any errors but its not scanning the info because when i print the info later on it prints out random symbols.