Hanging else problem?

Question

What is the "hanging else" problem? (Is that the right name?)

Following a C++ coding standard (forgot which one) I always use brackets (block) with control structures. So I don't normally have this problem (to which "if" does the last(?) else belong), but for understanding possible problems in foreign code it would be nice with a firm understanding of this problem. I remember reading about it in a book about Pascal many years ago, but I can't find that book.

Answer 1

Ambiguous else.

Some info here: http://theory.stanford.edu/~amitp/yapps/yapps-doc/node3.html

But the classic example is:

if a then
  if b then
     x = 1;
  else 
     y = 1;

vs.

if a then
  if b then
     x = 1;
else 
  y = 1;