i don't know what's wrong with my code. Trying to convert from string to long

Question

INPUT int main(void) { long long cardnumber, calc; string credit[0]; string nonnumeric; //long long calc = card number; int countcardcharacters = 0; long long c;

//user input
do
{
    credit[0]= get_string("Card number: ");
}
while (credit < 0);

printf("%lli\n", cardnumber);


/*checksum(long long calc);
{
    
}*/



cardnumber = long long strtoll(const char credit, &nonnumeric, 10);
calc = cardnumber;
//credit[0] = cardnumber;
//printf("%li\n", credit[0]);

//amex
if (strlen(credit[0]) == 15)
{
    while (credit[0][0] == 3 && (credit[0][1] == 4 || credit[0][1] == 7))
    {
        //american express
        printf("lol");
    }
}

OUTPUT clang -ggdb3 -O0 -std=c11 -Wall -Werror -Wextra -Wno-sign-compare -Wno-unused-parameter -Wno-unused-variable -Wshadow credit.c -lcrypt -lcs50 -lm -o credit credit.c:33:18: error: expected expression cardnumber = long int strtoll(const char credit, &nonnumeric, 10); ^ 1 error generated. : recipe for target 'credit' failed

Answer 1

The reason that this

cardnumber = strtoll (credit, NULL, 10)

gives this error

error: incompatible pointer types passing 'string [0]' to parameter of type 'const char *' 

is because the variable credit has been declared an array of strings with 0 members here

string credit[0];

I am inclined to think that was not the intention. Prompting the user for a string with get_string is much the same as prompting the user for an integer with get_int as would have been done in mario. Here is the example from the source code that accompanies the lecture to use as a guide.

    // get_string and printf with %s 

        #include<cs50.h> 
        #include<stdio.h> 

       intmain(void) 
       { 
            string s = get_string("What's your name?\n"); 
            printf("hello, %s\n", s);
       }