basic routines for ContFrac

contfrac.h

@@ -25,17 +25,45 @@
 
 namespace LA {
 
+//simple finite continued fraction class
+//NOTE: 0 on any position >0 means actually infinity; simplify()  shortens the vector
+//presently implements just conversion to/from rationals and floats
+//maybe implement arithmetic by Gosper's method cf. https://perl.plover.com/classes/cftalk/TALK
+
+template <typename T>
+class Rational {
+public:
+	T num;
+	T den;
+
+	Rational(const T p, const T q) : num(p),den(q) {};
+};
 
 template <typename T>
 class ContFrac : public NRVec<T> {
+private:
+	int size() const; //prevent confusion with vector size
 public:
 	ContFrac():  NRVec<T>() {};
 	template<int SIZE>  ContFrac(const T (&a)[SIZE]) : NRVec<T>(a) {};
 	ContFrac(const NRVec<T> &v) : NRVec<T>(v) {}; //allow implicit conversion from NRVec
 	ContFrac(const int n) : NRVec<T>(n+1) {};
+	ContFrac(double x, const int n, const T thres=0); //might yield a non-canonical form
+	ContFrac(const T p, const T q); //should yield a canonical form
+	ContFrac(const Rational<T> r) : ContFrac(r.num,r.den) {};
 
+	void canonicalize();
+	void convergent(T *p, T*q, const int trunc= -1) const;
+	Rational<T> rational(const int trunc= -1) const {T p,q; convergent(&p,&q,trunc); return Rational<T>(p,q);};
+	double value(const int trunc= -1) const;
+	ContFrac reciprocal() const;
 	int length() const {return NRVec<T>::size()-1;};
-	void resize(const int n, const bool preserve=true) {NRVec<T>::resize(n+1,preserve);}
+	void resize(const int n, const bool preserve=true) 
+		{
+		int nold=length();
+		NRVec<T>::resize(n+1,preserve);
+		if(preserve) for(int i=nold+1; i<=n;++i) (*this)[i]=0;
+		} 
 	
 };