618: Mainline

Suppose, for example, that you decide to write a function that constructs trades, similar to the one defined in Segment 385:

/* Define trade structure */ 
struct trade { 
    double price; 
    int number; 
}; 
/* Define constructor for trade structures */ 
struct trade* construct_trade (double price, int number) { 
  struct trade *tptr; 
  tptr = (struct trade*) malloc (sizeof (struct trade)); 
  tptr -> price = price; 
  tptr -> number = number; 
  return tptr; 
} 

In contrast, you want the new version of construct_trade to be able to handle the following cases:

• As before, you supply both a price and a number of shares.
• Alternatively, you supply just a price, with the number of shares taken to be 100 by default.