Discussion Session 6

Lazy Evaluation

Procedure definition and invocation

• procedure(name, body)
• call(name)

Tail Call Optimization

Example 1:

procedure foo1 {
  print 1;
  call foo2;
  print 11;
}
procedure foo2 {
  print 2;
  call foo3;
}
procedure foo3 {
  print 3;
}
call foo1;

Example 2:

procedure foo1 {
  print 1;
  call foo1;
}
call foo1;

While loop and recursive tail call is equivalent.

Discussion

What’s the benefit?