/* -------------------------------------------------------------------------  
//  Figure 3.17:  Problem solution: Gas prices.                                              
//                Compute the equivalent prices for Canadian gas and US gas.        
// ------------------------------------------------------------------------- 
*/
#include <stdio.h> 
#define  LITR_GAL    3.78544 

void main( void ) 
{               
    double US_per_Can;      /*  Exchange rate, $_US / $_Canadian */     
    double C_liter;         /*  Canadian dollars per liter */ 
    double D_gallon;        /*  US dollars per gallon  */ 

    puts( "\n Gas Price Conversion Program \n" ); 
    printf( " Enter the exchange rate, &US per $Can: " ); 
    scanf( "%lg", &US_per_Can );
    while (US_per_Can < 0.0) {
        printf( " Re-enter, &US per $Can rate must be positive: " );
        scanf( "%lg", &US_per_Can );
    }

    printf( " Canadian price per liter: " ); 
    scanf( "%lg", &C_liter );
    while (C_liter < 0.0) {
        printf( " Re-enter; price must be positive: " ); 
        scanf( "%lg", &C_liter );
    }

    D_gallon = C_liter * LITR_GAL * US_per_Can; 
    printf( "\n Canada: $%g  USA: $%g \n", C_liter, D_gallon );
    puts( "\n Normal termination.\n" );
}