Index: src/libcfa/rational
===================================================================
--- src/libcfa/rational	(revision 3d9b5dab248af2c0f972053139d0a12c951786d0)
+++ src/libcfa/rational	(revision e55ca0532660df6b168cbfe023499f87bda57a53)
@@ -5,30 +5,38 @@
 // file "LICENCE" distributed with Cforall.
 // 
-// rational -- 
+// rational -- Rational numbers are numbers written as a ratio, i.e., as a fraction, where the numerator (top number)
+//     and the denominator (bottom number) are whole numbers. When creating and computing with rational numbers, results
+//     are constantly reduced to keep the numerator and denominator as small as possible.
 // 
 // Author           : Peter A. Buhr
 // Created On       : Wed Apr  6 17:56:25 2016
 // Last Modified By : Peter A. Buhr
-// Last Modified On : Thu Apr  7 17:23:36 2016
-// Update Count     : 9
+// Last Modified On : Fri Apr  8 11:38:27 2016
+// Update Count     : 15
 // 
 
 #include "iostream"
 
+// implementation
 struct Rational {
 	long int numerator, denominator;					// invariant: denominator > 0
 }; // Rational
 
+// constants
 extern struct Rational 0;
 extern struct Rational 1;
 
-long int gcd( long int a, long int b );
-long int simplify( long int *n, long int *d );
-Rational rational();									// constructor
-Rational rational( long int n );						// constructor
-Rational rational( long int n, long int d );			// constructor
+// constructors
+Rational rational();
+Rational rational( long int n );
+Rational rational( long int n, long int d );
+
+// getter/setter for numerator/denominator
 long int numerator( Rational r );
 long int numerator( Rational r, long int n );
+long int denominator( Rational r );
 long int denominator( Rational r, long int d );
+
+// comparison
 int ?==?( Rational l, Rational r );
 int ?!=?( Rational l, Rational r );
@@ -37,4 +45,6 @@
 int ?>?( Rational l, Rational r );
 int ?>=?( Rational l, Rational r );
+
+// arithmetic
 Rational -?( Rational r );
 Rational ?+?( Rational l, Rational r );
@@ -42,6 +52,10 @@
 Rational ?*?( Rational l, Rational r );
 Rational ?/?( Rational l, Rational r );
+
+// conversion
 double widen( Rational r );
 Rational narrow( double f, long int md );
+
+// I/O
 forall( dtype istype | istream( istype ) ) istype * ?|?( istype *, Rational * );
 forall( dtype ostype | ostream( ostype ) ) ostype * ?|?( ostype *, Rational );