Question

program Project1;
var 
  a,b:set of byte;
  c:set of byte;
  i:integer;

begin
  a:=[3]; 
  b:=[2]; 
  c:=(a+b)*(a-b);
  FOR i:= 0 TO 5 DO
    IF i IN c THEN write(i:2);
  readln;
end.

有人可以向我解释一下这段代码中发生了什么。我知道c = 3但不明白a和b的值是什么？试过writeln(a,b);但是给了我一个错误......

Answer 1

好的，我会解释你可能通过调试找到的东西，或者只是简单地阅读Pascal上的教科书：

该行：

c := (a+b)*(a-b);

执行以下操作：

a + b is the union of the two sets, i.e. all elements that are 
      in a or in b or in both, so here, that is [2, 3];
a - b is the difference of the two sets, i.e. it is a minus the
      elements of a that happen to be in b too. In this case, no 
      common elements to be removed, so the result is the same as a, 
      i.e. [3]
x * y is the intersection of the two sets, i.e. elements that are in 
      x as well as in y (i.e. a set with the elements both have in common).

说，x := a + b; y := a - b;，然后可以将其视为：

x := a + b; // [3] + [2] --> [2, 3]
y := a - b; // [3] - [2] --> [3]
c := x * y; // [2, 3] * [3] --> [3]

一组字节，a和b的值是什么

1 个答案: