/*
  interval.hh -- part of flowerlib
  
  (c) 1996 Han-Wen Nienhuys
*/

#ifndef INTERVAL_HH
#define INTERVAL_HH

#include <assert.h> 
#include "fproto.hh"
#include "real.hh"


/** a T interval.  this represents the closed interval [left,right].
  No invariants. T must be a totally ordered ring (with division, anyway ..)
  At instantiation, the function infinity() has to be defined explicitely.
  
  */
template<class T>
struct Interval_t {
  T left, right;

  /* ************** */
    
  static T infinity() ;
  static String T_to_str (T arg);
    
  // ugh, egcs 1.02 ices on this
//  T center() { return (left + right) / T(2);}
  // and can't handle this either
  // anyone want to make a bug report?
  // better make one soon, egcs in rh5.1 barfs on this!
  T center() {
    T two (2);
//    return (left + right) / two;
    T result ((left + right) / two);
    return result;
  }
  void translate (T t) {
    left += t;
    right += t;
  }
  T& idx (int j) {
    if (j==-1)
      return left;
    else if (j==1)
      return right;
    else
      assert (false);
    return left;		
  }
  T& operator[](int j) {
    return idx (j);
  }
  T operator[](int j) const {
    return ((Interval_t<T> *)this)->idx (j);
  }
  T &max() { return right;}
  T max() const { return right;}
  T min() const{ return left; }
  T &min(){ return left; }
  /**
    PRE
    *this and h are comparable
    */
  void unite (Interval_t<T> h);
  void intersect (Interval_t<T> h);

  T length() const;
  void set_empty() ;
  bool empty_b() const { return left > right; }
  bool contains_b (Interval_t<T> const&) const;
  Interval_t() {
    set_empty();
  }
  Interval_t (T m, T M) {
    left =m;
    right = M;
  }
  Interval_t<T> &operator -= (T r) {
    *this += -r;
    return *this;
  }

  Interval_t<T> &operator += (T r) {
    left += r;
    right +=r;
    return *this;
  }
  Interval_t<T> &operator *=(T r) {
    left *= r;
    right *= r;
    if (r < T(0)) {
      T t = left;
      left = right;
      right = t;
    }
    return *this;
  }
  String str() const;    
  void print () const;
  bool elt_b (T r);
  void negate () {
    T r = -left;
    T l = -right;
    left = l;
    right =r;
  }
};


/**
  inclusion ordering. Crash if not comparable.
  */
template<class T>
int Interval__compare (const Interval_t<T>&,Interval_t<T> const&);

/*
  INLINE
 */

#include "compare.hh"

TEMPLATE_INSTANTIATE_COMPARE(Interval_t<T>&, Interval__compare, template<class T>);


template<class T>
inline Interval_t<T>
intersection (Interval_t<T> a, Interval_t<T> const&b)
{
  a.intersect (b);
  return a;
    
}

template<class T>
inline
Interval_t<T> operator +(T a,Interval_t<T> i)
{
  i += a;
  return i;
}

template<class T>
inline
Interval_t<T> operator - (Interval_t<T> i, T a)
{
  i += -a;
  return i;
}

template<class T>
inline
Interval_t<T> operator - (T a,Interval_t<T> i)
{
  i.negate ();
  i += a;
  return i;
}

template<class T>
inline
Interval_t<T> operator +(Interval_t<T> i,T a){
  return a+i;
}

template<class T>
inline
Interval_t<T> operator *(T a,Interval_t<T> i)
{
  i *= a;
  return i;
}

template<class T>
inline
Interval_t<T> operator *(Interval_t<T> i,T a){
  return a*i;
}

// again? see fproto.hh
typedef Interval_t<Real> Interval;
typedef Interval_t<int> Slice;


#endif // INTERVAL_HH

