443: Mainline

Many programmers use typedef synonyms for user-defined structures, but not for the built-in data types. The following, for the sake of illustration, uses typedef synonyms for both:

#include   
/* Define the trade apparatus */ 
struct trade {double price; int number;}; 
/* Define enumeration constants, needed in switch statement */ 
enum {food, trucking, computers, metals, health, airline}; 
/* Define types */ 
typedef struct trade Trade_description; 
typedef int Industry_code; 
typedef int Number_of_shares_traded; 
typedef double Price_per_share_traded; 
typedef double Total_cost_of_trade; 
/* Define trade array */ 
Trade_description *trade_pointers[100]; 
/* Define price-computing function */ 
Total_cost_of_trade trade_price (Trade_description *x) { 
  return x -> price * x -> number; 
} 
main ( ) { 
  /* Declare various variables */ 
  int limit, counter; 
  double sum = 0.0; 
  Industry_code industry; 
  Price_per_share_traded price; 
  Number_of_shares_traded number; 
  /* Read trade information and compute cost */ 
  for (limit = 0; 3 == scanf ("%i%lf%i", &industry, &price, &number);) 
    switch (industry) { 
      case trucking: case airline: 
        trade_pointers[limit] = 
          (Trade_description*) malloc (sizeof (Trade_description)); 
        trade_pointers[limit] -> price = price; 
        trade_pointers[limit] -> number = number; 
        ++limit; 
        break; 
      case food: case computers: case metals: case health: 
        break; 
      default: printf ("Industry code %i is unknown!\n", industry);  
               exit (0); 
    } 
  for (counter = 0; counter < limit; ++counter) 
    sum = sum + trade_price (trade_pointers[counter]); 
  printf ("The total cost of %i selected trades is %f.\n", 
                             limit,                sum); 
} 
--- Data ---
0  3.3  300 
1  2.5  400 
5  9.9  100 
5 10.1  100 
2  5.0  200 
--- Result --- 
The total cost of 3 selected trades is 3000.000000.