//--------------------------------------------------------------------
// funcptr.cpp
//--------------------------------------------------------------------


// Examples showing the use of pointers as function parameters and
// of functions that return a pointer.

#include <iostream.h>

// Function prototypes
void printSum ( int *numPtr1, int *numPtr2 );
void swap ( int *numPtr1, int *numPtr2 );
void copyString ( char *dest, char *source );
char *match ( char *str, char searchCh );

//--------------------------------------------------------------------


void main()
{
    int val1 = 10,               // Sample integer values
        val2 = 20;
    char alpha[11] = "alpha",    // Sample strings
         beta[11];
    char sample[11] = "Sample",
         *ptr;

    // Prints the sum of two integer values.
    cout << endl << "The sum of val1 and val2 is ";
    printSum(&val1,&val2);

    // Swaps two integer values.
    swap(&val1,&val2);
    cout << "After swapping" << endl;
    cout << "val1: " << val1 << endl << "val2: " << val2 << endl;


    // Copy alpha to beta.
    copyString(beta,alpha);
    cout << "After copying" << endl;
    cout << "alpha: " << alpha <<
endl << "beta: " << beta << endl;


    // Find a match for character 'p' in sample.
    ptr = match(sample,'p');
    cout << "Match character: " << *ptr << endl;
}

//--------------------------------------------------------------------


void printSum ( int *numPtr1, int *numPtr2 )
// Outputs the sum of the integer values pointed to by numPtr1 and
// numPtr2.
{
    cout << *numPtr1 + *numPtr2 << endl;
}

void swap (int *numPtr1, int *numPtr2)
// Exchanges the integer values pointed to by numPtr1 and numPtr2.
{
    int temp;

    temp = *numPtr1;
    *numPtr1 = *numPtr2;
    *numPtr2 = temp;
}

void copyString ( char *dest, char *source )
// Copies source string to dest string buffer. Note that strings
// source and dest are passed using pass-by-reference.
{
    while ( *source != '\0' )    // Stop when null reached in source
    {
        *dest = *source;   // Copy character
        source++;          // Advance to next character in source
        dest++;            // Advance to next character in dest
    }
    *dest = '\0';          // Add null character to dest
}

/*

void copyString ( char *dest, char *source )
// Copies source string to dest string buffer. Uses the subscript
// operator to access the characters in the strings.
{
    int index = 0;
    while ( source[index] != '\0' )    // Stop when null is reached
    {
        dest[index] = source[index];   // Copy character
        index++;                       // Advance to the next character
    }
    dest[index] = '\0';                // Add null character to dest
}

*/

char *match ( char *str, char searchCh )
// Returns a pointer to the first character in string str that
// matches character searchCh. If there are no matches, then
// returns the null pointer.
{
    char *matchPtr = str;   // Pointer returned

    // Search for searchCh by advancing matchPtr through the string.
    while ( *matchPtr != searchCh  &&  *matchPtr != '\0' )
        matchPtr++;

    if ( *matchPtr == '\0' )
        matchPtr = 0;           // searchCh not found, return null

    return matchPtr;
}