statically and dynamically scopes

问题

I'm working on this problem and I got the answers :

Statically: 20, 16

Dynamically: 20, 100

is that correct?

Consider the program below (in a Pascal like language). What is the output of the language is statically scoped? What is the output if the language is dynamically scoped?

Program main;
   x: integer;
procedure f1(z: integer)
begin 
       return z * x;
   end
procedure f2(z: integer)
      int x;
   begin
       x = 2;
       return f1(z)  * x;
   end

begin /* main program */
   x = 5;
print f1(4);
   print f2(4);
end

回答1:

Why not try out both versions? Using Perl with static scope:

my $x = 5;
sub f1($) {
  my $z = shift;
  return $z * $x;
}
sub f2($) {
  my $z = shift;
  my $x = 2;
  return f1($z) * $x;
}
print f1(4), "\n";
print f2(4), "\n";

I get 20, 40. (20 being 4 * 5, 40 being (4 * 5) * 2.)

Replacing all the mys with locals to get dynamic scope, I get 20, 16. (20 being 4 * 5, 16 being (4 * 2) * 2.)

Unfortunately, since you only posted your conclusions, no explanation, I can't point out where you went wrong . . .

来源：https://stackoverflow.com/questions/9421863/statically-and-dynamically-scopes

标签

dynamic