looping through a character array c++ [closed] - c++

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#include <iostream>
#include <string>
using namespace std;
bool custNum(char [], int);
int main()
{
const int size = 8;
char custmor[size];
cout << "Enter a customer number in the form ";
cout << "LLLNNNN\n";
cout << "(LLL = letters and NNNN = numbers): ";
cin.getline(custmor, size);
if(custNum(custmor, size))
cout<<"That's a valid id number"<<endl;
else
cout<<"That's not a valid id number"<<endl;
return 0;
}
bool custNum(char custNum[], int size)
{
int count;
for(count = 0; count<3; count++)
{
if(!isalpha(custNum[count]))
return false;
}
for(count = 3; count <size - 1; count++) //3<7 , 4
{
if(!isdigit(custNum[count]))
return false;
}
return true;
}
so I want to loop through a character array of 3 letters and 4 numbers like ABC1234, but I didn't get the condition of the second for loop (size - 1). How does it work every time it tests the condition?

Answer 1

Never use count as a loop variable. A good name for a loop variable is i.
Never declare variables away from their initialization. The above should be for( int i = 0; ... in both cases.
i < size - 1 is probably wrong. What you probably want is i < size.
Anyhow, it would help if you showed how size is declared, how it is initialized, etc. It would also help if you showed the exact text you are trying to parse. It would also help if you explained exactly what you expected to happen, and exactly what happened instead. I might amend my answer when you do that.

Answer 2

you read only amount of characters that size variable specify,
since then , Why custNum function would not return true for anything longer than size variable ? , Because it's not checking anything more than what size variable specify.
Below is the code you need
#include <iostream>
#include <string>
using namespace std;
bool custNum(string,unsigned int);
int main()
{
const unsigned int size = 8;
//char custmor[size];
string mystring;
cout << "Enter a customer number in the form ";
cout << "LLLNNNN\n";
cout << "(LLL = letters and NNNN = numbers): ";
cin >> mystring;
cout << mystring <<endl << " " << mystring.length() << endl;
// cin.getline(custmor, size);
if(custNum(mystring , size))
cout<<"That's a valid id number"<<endl;
else
cout<<"That's not a valid id number"<<endl;
return 0;
}
bool custNum(string s, unsigned int size)
{
unsigned int count;
if (s.length() != (size + 1))
return false;
for(count = 0; count<3; count++)
{
if(!isalpha(s[count]))
return false;
}
for(count = 3; count <size - 1; count++) //3<7 , 4
{
cout << s[count] <<endl;
if(!isdigit(s[count]))
return false;
}
return true;
}