#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdarg.h>

#define absVal(x)   ( ( (x)>0 ) ? (x) : -(x) )

#define printInt(expr)  printf("Line %d: %s=%d\n", \
                        __LINE__, #expr, expr )
#define printArrayItem(arr,idx)  printf("%s[%d]=%d\n", \
                        #arr, idx, arr[idx] )

int zz;

void printStrings( const char *str1, ... )
{
    const char *nextStr;
    va_list argp;

    printf( "%s\n", str1 );
    va_start( argp, str1 );

    while( ( nextStr = va_arg( argp, const char * ) ) != NULL )
        printf( "%s\n", nextStr );

    va_end( argp );
}

int (absVal)( int x )
{
    return x > 0 ? x : -x;
}

int square( int x )
{
    return x * x;
}

int cube( int x )
{
    return x* x * x;
}


struct function
{
    char *functionName;
    int ( * ptrToF ) ( );
};

struct function fs[ ] = { { "cube", cube },
                          { "abs", absVal },
                          { "absVal", absVal },
                          { "square", square }
                        };

int invokeFunction( const char *name, int x )
{
    int i;
    int numFunctions = sizeof( fs ) / sizeof( fs[ 0 ] );

    for( i = 0; i < numFunctions; i++ )
        if( strcmp( name, fs[ i ].functionName ) == 0 )
            return ( *fs[ i ].ptrToF )( x );

    printf( "OOPS!!! BAD FUNCTION NAME\n" );
    return 0;
}

int intCompare( const void * lhs, const void * rhs )
{
    int first = *(int *)lhs;
    int second = *(int *)rhs;

    if( first < second )
        return -1;
    else
        return first > second;
}

int main( )
{
    int x = 3;
    int y = -5;
    int arr[ ] = { 8, 4, 1, 12, 7, -3 };
    int *ptr;
    int ARR_SIZE = sizeof( arr ) /sizeof( arr[ 0 ] );
    int i;

    printInt( absVal( x ) );
    printInt( absVal( y ) ) ;
    printInt( 5 * absVal( x+y ) );
    printInt( (absVal)( ++x ) );

    printInt( invokeFunction( "square", -7 ) );
    printInt( invokeFunction( "abs", -4 ) );
    printInt( invokeFunction( "absVal", -4 ) );
    printInt( invokeFunction( "cube", 10 ) );

    for( i = 0; i < ARR_SIZE; i++ )
        printInt( arr[i] );

    qsort( arr, ARR_SIZE, sizeof( arr[ 0 ] ), intCompare );

    ptr = arr;
    for( i = 0; i < ARR_SIZE; i++ )
        printArrayItem( ptr, i );


    printStrings( "This", "is", "a", "test", ( const char *) NULL );

    return 0;
}