/* This program demonstrates
 * 1. c-style strings
 * 2. The input stream and how it interacts with cin
 *
 * * A string is the word programmers use to represent text.
 * We can store a single character in a char variable. To store many characters (text),
 * we need multiple char variables. The quick solution to this is to use an
 * array of characters. An array of chars is called a C-String.
 * Since C-Strings are arrays, every concept that applies to arrays also applies
 * to C-Strings. So, a C-String has elements in contiguous memory locations,
 * we can access individual elements using the index, the index starts at 0.
 *
 * There are 4 major points of difference between a regular numeric array we are
 * familiar with and a C-String
 * 1. End-of-String: If we have a regular numeric array, and we have fewer values
 * than spots allocated, then the rest of the spots are filled out with 0's (if
 * we initialize the array) or with junk values (if we do not initialize). In
 * case of C-Strings, the spot  after the last value is assigned the end-of-string
 * character. The end-of-string character is '\0'. C++ considers all the characters
 * from position 0 until the end-of-string to be the string.
 *
 * 2. Direct initialization: If we want to initialize a numeric array, we have
 * to use set notation upon declaration. However, for strings we can either use
 * the set notation or use a double quoted string literal.
 *
 * 3. Direct printing: It is not possible to directly print a numeric array.
 * If we tried, we would just get the starting address of the array. However,
 * we can directly print a C-String (put it in the cout without using a loop).
 *
 * 4. Direct reading: We cannot directly read in the entire numeric array. However,
 * we can use a cin statement to read in the C-string (instead of using a loop).
 *
 * A Note on streams:
 * cin reads from the input stream (stdin), which sends data from the
 * keyboard to our program. To save time and make this process more efficient
 * the input stream will send in what we typed only when we press the Enter key.
 * So, multiple pieces of information could be sent to the input stream (cin)
 * However, cin in whitespace delimited. It will read from the first character
 * remaining on the stream until the first whitespace character. If any charatcer
 * does not match wha cin is expecting, it will crash.
 * When we use cin with a string just like we use it with numbers, it will
 * read until it encounters the first whitespace character. So, it is capable of
 * reading only one "word"
 */

#include<iostream>
#include<cctype> // for query functions
#include<cstring> // for string length

using namespace std;

int main()
{
    //Declare a C-string and initialize it with set notation
    char str[100] = {'H', 'e', 'l', 'l', 'o', '\0'};

    //Directly print a string
    cout<<"The string is "<<str<<endl;

    //Direct initialization with a quoted string
    char myString[50] = "Sample string";
    cout<<"myString is "<<myString<<endl;
    /* When we use direct initialization, C++ puts the '\0' at the end.
     * When we use set notation, we have to terminate the string. */

    // Directly read a string
    cout<<"Enter a string: ";
    cin>>str;

    cout<<"You entered "<<str<<endl;

    char st1[50];
    cout<<"Enter another string: ";
    cin>>st1;

    //We can also print individual characters
    // C++ does not check for bounds, we have to do it ourselves.
    for(int i=0; i<100 ; i++)
        cout<<st1[i] <<" ";

    cout<<"\nActual Print: "<<st1<<endl;

    int x, y;
    char st[100];
    cout<<"Enter a number: ";
    cin>>x;

    cout<<"Enter a string: ";
    cin>>st;

    cout<<"Enter another number: ";
    cin>>y;

    cout<<"x: "<<x<<"\nst: "<<st<<"\ny: "<<y<<endl;

    /* To read in multiple words, we can use a function that is a part of cin, called
    * getline. However, this will also read the newline left behind in the stream,
    * after our previous input. To get rid of this newline, we use another
    * function that is a part of cin, called ignore.
    * getline takes 3 parameters, the string, the maximum number of characters
    * we want to read and the character we want to stop at. The last one is a
    * default parameter with the default value of '\n'.
    * cin.getline will read until it reaches the maximum number of characters
    * or the termination character, whichever is earlier. The delimiter
    * character is then removed from the stream.*/

    // cin.getline(junk, 20, '\n');
    char st2[20];
    cin.ignore();
    cin.getline(st, 100);
    cin.getline(st2, 20, '\n');

    cout<<"st is now "<<st<<endl;
    cout<<"st2: "<<st2<<endl;

    /* We can print the length of a string using the strlen function fromt he cstring library */
    cout<<"Length of st is "<< strlen(st)<<endl;
    
    /* The query functions in the cctype library only work on individual characters */
    cout<<"Is the first character of st uppercase? "<< isupper(st[0])<<endl;
    
    return 0;
}