Hi CS50 gang!

I'm really enjoying the course, but my brain hurts already at week 2. I've noticed an error when compiling a programme in C when I try to declare a variable inside a FOR loop in C (example below).

I just move my variable declaration to above the FOR loop, but I have two questions about this:

1. Why does this happen? Is it because the loop tries to declare the variable each time it iterates?

2. Does it cause problems to declare the variable (int letter_count) above the loop, like I have done in the example below? Or is there a better convention for declaring variables?

 int letter_count = 0;
    //loop to break text string into chars
    for (int i = 0, n = strlen(text); i < n; i++)
    {
        //check if char i is lower or upper and increment letter-count by 1 if true
        if (isupper(text[i]) || islower(text[i]))
        {
            letter_count++;
        }
        
        printf("%c", text[i]);
    }

Thank you!

I am getting this error numerous times in one file which leads me to think that its a simple thing im over looking yet I cannot find a solution to the problem. Any help is greatly appreciated.

I have a post.cpp and post.h (post.h is causing the problem) and it is giving the same error plus others. Please see the list here;

https://ibb.co/VBFc581

I have another class User - all the errors are related to this class for some reason. I am not getting any errors highlighted in the code file in VS only when I run the compiler. I will include the first error here as I dont want to post loads of code to make it hard to solve.

The Post class first error is std::vector<User*> taggesUsers; - you can see it has User in it.

#include "pch.h"

class Post
{
	std::string poster;
	time_t dateTime = DkDateTime::getTimeNow();
	std::string message;
	std::list<std::string> tags;
	std::vector<User*> taggesUsers;

My pch.h

#include <iostream>
#include <string>
#include <vector>
#include <list>


#include "DkDateTime.h"
#include "User.h"
#include "Post.h"

and my user

#pragma once

#include"pch.h"


class User
{
	//Class members
	std::string email;
	std::string password;
	std::string userName;
	time_t lastLogin = DkDateTime::getTimeNow();;

public:

	//Constructor
	User();
	User(std::string email, std::string password, std::string userName);
	~User();

	//Get&Set
	std::string const getEmail() { return email; }
	std::string const getPassword() { return password; }
	std::string const getUserName() { return userName; }
	time_t getLastLogin() { return lastLogin; }

	void setEmail(std::string e) { email = e; }
	void setPassword(std::string p) { password = p; }
	void setUserName(std::string un) { userName = un; }
	void setLastLogin(time_t ll) { lastLogin = ll; }

	//Validation
	bool validateEmail(const std::string email);
	bool validatePassword(const std::string email);
	bool validateUserName(const std::string userName);

	//Overloads
	friend std::ostream& operator<<(std::ostream &out, const User &usr);
	friend std::istream& operator>>(std::istream& in, User& usr);

};

I hope that if you can solve the first error I can get the rest as it seems to be anywhere in the Post.h file I use my User class.

So I've just learned about inheritance in my C++ programming class, and for one of my personal projects I wanted to create a card game. I have an object, 'aDeck', which I want to be a vector of 'aCard' objects.

This is what my .h file for the aDeck class looks like.

#pragma once

#include <vector>
#include "aCard.h"

using namespace std;

class aDeck : public vector<aCard>
{
    public:
    	aDeck(int type);
    	~aDeck();
    	void drawCard(aDeck drawHand);
    	void populateHand(aDeck popHand);
    	void populateDiscard(aDeck gameDeck);
    
    	void outputAll();
    	void outputTop();
};

And this is the .h file for aCard

#pragma once

#include "aDeck.h"
#include <iostream>

using namespace std;

class aCard
{
	public:
		aCard();
		aCard(int color, int number);
		~aCard();
		void displayCard();
	private:
		int cardColor;
		int cardNumber;	
};

This, however, is giving me the error of: "error C2065: 'aCard' : undeclared identifier"

Google says this is because i'm not including the .h file for aCard, which I am. So what would cause something like this?

int total = 0;   
    for (int i= 0; word[i] != '\0'; i++)
    ;
    {
       char c = word[i];     
       if (isalpha(c))
           total += POINTS[get_index(c)];
    }    
    return total;
        
}

int get_index(char c)
{
    return tolower(c) - 'a';

When I compile the code I get undeclared identifier 'i'. But when declare it I get declaration shadows a variable in the global scope [-Werror,-Wshadow]. Please help

Hello, I'm new to programming and while coding my example program I ran into an issue that I've been trying to figure out how to resolve. When print_Menu_Info(); executes and it tries to execute print_Customer_Table(&c); I encounter the error in the title.

sales.c:101:24: error: use of undeclared identifier 'c'

Even though the line is being declared in line 12.

struct customer c = empty_customer;

#include <stdio.h>
#include <stdlib.h>
#include "sales.h"

int main(void)
{
    menu_update();
    return 0;
}

void menu_update(void){
    struct customer c = empty_customer;
	float f = 0.00;
	int i = 0;
	while (1) {
	    cls();
	    print_Menu_Info();
	    switch(get_User_Input()){
	        case 1:
				printf("Customer First Name: ");
				scanf("%s",c.first_Name);
	            break;
	        case 2:
				printf("Customer Last Name: ");
				scanf("%s",c.last_Name);
	            break;
	        case 3:
				printf("Customer Amount: ");
				scanf("%f",&f);
				c.amount = f;
	            break;
	        case 4:
				printf("Customer Card Number: ");
				scanf("%s",c.card_Number);
	            break;        
	        case 5:
				printf("Customer Card Expiration Month: ");
				scanf("%i",&i);
				c.card_Expiration_Month = i;
	            break;
	        case 6:
				printf("Customer Card Expiration Year: ");
				scanf("%i",&i);
				c.card_Expiration_Year = i;
	            break;
	        case 7:
				printf("Sales Person: ");
				scanf("%s",c.sales_Person);
	            break;
            case 8:
                print_Customer_Table(&c);
                break;
            case 9:
                c = empty_customer;
                break;
	        case 10:
	            exit(0);
	        default:
	            printf("Incorrect action ID!\n");
	            break;
	    }    
	}
}

void cls(void){
    printf("\033c");
}

int get_User_Input(){
	int a = 0;
    char line[32];
    printf("Please input an action ID: ");
	if (fgets(line, sizeof(line), stdin) != NULL) {
    	sscanf(line, "%i", &a);
    	cls();
    }
	return a;
}


void print_Customer_Table(struct customer *cp){
    printf(
    "1. Customer First Name: %s\n"
    "2. Customer Last Name: %s\n"
    "3. Customer Amount: $%.2f\n"
    "4. Customer Card Number: %s\n"
    "5. Customer Card Expiration Month: %i\n"
    "6. Customer Card Expiration Year: %i\n"
    "7. Sales Person: %s\n",
    cp->first_Name,
    cp->last_Name,
    cp->amount,
    cp->card_Number,
    cp->card_Expiration_Month,
    cp->card_Expiration_Year,
    cp->sales_Person);
}

void print_Menu_Info(void){
	print_Customer_Table(&c);
	printf(
	"If you would like to update a value type the value you would like to update(1-7)\n"
    "If you would like to send this as a email type 8\n"
    "If you would like to clear all customer data type 9\n"
    "If you would like to exit this program type 10\n");
}                

and sales.h

#define NAME_LEN_MAX 128
#define CARD_NUM_LEN_MAX 16
struct customer {
    char first_Name[NAME_LEN_MAX + 1];
    char last_Name[NAME_LEN_MAX + 1];
    float amount;
    char card_Number[CARD_NUM_LEN_MAX + 1];
    int card_Expiration_Month;
    int card_Expiration_Year;
    char sales_Person[NAME_LEN_MAX + 1];
};
const static struct customer empty_customer = {{""},{""},0.00,{""},0,0,{""}};
void print_Customer_Table(struct customer *cp);
void print_Menu_Info(void);
void cls(void);
int get_User_Input();
void menu_update(void);