Re: abusing exceptions

From:

Francis Glassborow <francis.glassborow@btinternet.com>

Newsgroups:

comp.lang.c++.moderated

Date:

Sat, 15 Dec 2007 16:54:23 CST

Message-ID:

<Jcadne2xfuvQWv7anZ2dnUVZ8uidnZ2d@bt.com>

Jerry Coffin wrote:

Both of these have the same problem. The OP's code is NOT like either
one of these though. His code works roughly like this:

void recur(int depth) {
    if (depth == 0)
        return;
    throw(depth-1);
}

void recur_entry(int depth) {
    while (depth > 0) {
        try {
            recur(depth);
        }
        catch(int x) {
            depth = x;
        }
    }
}

(He put the current depth into a struct and throws an instance of the
struct, but the call structure isn't affected).

Well if that really is the structure of his code then it should be
written as:

void recur_entry(int depth){
    while (depth > 0) {
      try {
          //do something
throw (depth - 1)
      }
      catch(int x) {
        depth = x;
      }
    }
}
Which has a 0 call depth.

At which point it is clear that recursion is the wrong way to go because
that is equivalent to:

void recur_entry(int depth){
    if (depth < 1) throw invalid_argument;
    while (depth > 0) {
         //do something
         --depth;
    }
}

So clearly I still do not understand his code.

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