Cannot print returned value in C - c

Question

I ran compile this:
char get_credit_card_status(long long credit_card_number, char Luhn_validity)//, char credit_card_status)
{
char credit_card_status = 0;
if (((credit_card_number < 350000000000000) && (340000000000000 <=credit_card_number)) && (Luhn_validity=1))
{
credit_card_status = 1;
printf("1 test\n");
}
else if ((5100000000000000<= credit_card_number) && (credit_card_number < 5500000000000000) && Luhn_validity)
{
credit_card_status = 2;
printf("2 test\n");
}
else if ((((4000000000000<= credit_card_number)&&(credit_card_number<5000000000000)) || ((4000000000000000<=credit_card_number)&&(credit_card_number<5000000000000000))) && Luhn_validity)
{
credit_card_status= 3;
printf("3 test\n");
}
return credit_card_status;
}
int length_ccn(long long credit_card_number)
{
int length = 0;
while (credit_card_number > 0)
{
length++;
credit_card_number /= 10 ;
}
return length;
}
char Luhn_check(long long credit_card_number)
{
int total_even_numbers = 0;
int total_odd_numbers = 0;
int even_number = 0;
int odd_number = 0;
int Luhn_sum = 0;
char Luhn_validity = 0;
long long check_digit_basis = credit_card_number;
for(int i =1 ; check_digit_basis > 0 ; i++)
{
if ((i % 2) > 0)
{
odd_number = (check_digit_basis % 10);
total_odd_numbers = total_odd_numbers + odd_number;
}
else
{
even_number = (check_digit_basis % 10);
if(even_number >= 5)
{
total_even_numbers = total_even_numbers + ((( 2 * even_number) % 10) + 1 );
}
else
{
total_even_numbers = total_even_numbers + (2 * even_number);
}
}
check_digit_basis = (check_digit_basis / 10);
}
Luhn_sum = total_even_numbers + total_odd_numbers;
if ((Luhn_sum % 10 ) == 0 )
{
Luhn_validity = 1;
}
else
{
Luhn_validity = 0;
printf("%c for Luhn_validity\n", Luhn_validity);
}
printf("%d for Luhn_validity\n", Luhn_validity);
return Luhn_validity;
}
int main(void)
{
printf("Provide your credit card number:\n");
long long credit_card_number = get_long_long();
int length = length_ccn(credit_card_number);
printf("%i for length\n", length);
char Luhn_validity = Luhn_check(credit_card_number);
printf("%c returned from line 119\n", Luhn_validity);
char credit_card_status;
credit_card_status = get_credit_card_status(credit_card_number, Luhn_validity);
switch (credit_card_status)
{
case 1:
printf("American Express\n");
break;
case 2:
printf("MasterCard\n");
break;
case 3:
printf("Visa\n");
break;
default:
printf("INVALID\n");
}
}
I got:
15 for length
1 for Luhn_validity
returned from line 119
The value of Length is returned to the main function while Luhn_validity isn't. Why?
I cannot make another post because someone posted an incomplete answer only answering to what I already began to implement (see the post before its edits and you'll see that the boolean problem was being corrected and wasn't in the post's title).

Answer 1

credit_card_status = credit_card_status(credit_card_number)
You try to use the same name, credit_card_status, for two different things. If the function is called credit_card_status don't store it's return value in credit_card_status, because that's the function and not a variable. This leads to the error that credit_card_status is not assignable.
error: comparison of constant 350000000000000 with boolean expression is always true
There is no "twoway" comparison a <= x < b in C, you have to use two separate comparisons: a <= x && x < b.