//LISTING 1
#ifndef CTASSERT_H
#define CTASSERT_H

// Use of ctassert<E>, where E is a constant expression,
// will cause a compile-time error unless E evaulates to
// a nonzero integral value.

template <bool t>
struct ctassert {
  enum { N = 1 - 2 * int(!t) };
    // 1 if t is true, -1 if t is false.
  static char A[N];
};

template <bool t>
char ctassert<t>::A[N];

#endif