[Gnucash-changes] add clarifying documentation

[Linas Vepstas]

Log Message:
-----------
add clarifying documentation

Modified Files:
--------------
    gnucash/src/engine:
        gnc-numeric.h

Revision Data
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Index: gnc-numeric.h
===================================================================
RCS file: /home/cvs/cvsroot/gnucash/src/engine/gnc-numeric.h,v
retrieving revision 1.17
retrieving revision 1.18
diff -Lsrc/engine/gnc-numeric.h -Lsrc/engine/gnc-numeric.h -u -r1.17 -r1.18
--- src/engine/gnc-numeric.h
+++ src/engine/gnc-numeric.h
@@ -176,7 +176,15 @@
                             gint64 denom, gint how);
 gnc_numeric gnc_numeric_mul(gnc_numeric a, gnc_numeric b, 
                             gint64 denom, gint how);
-gnc_numeric gnc_numeric_div(gnc_numeric a, gnc_numeric b, 
+
+/** Division.  Note that division can overflow, in the following 
+ *  sense: if we write x=a/b and y=c/d  then x/y = (a*d)/(b*c)  
+ *  If, after eliminating all common factors between the numerator 
+ *  (a*d) and the denominator (b*c),  then if either the numerator 
+ *  and/or the denominator are *still* greater than 2^63, then 
+ *  the division has overflowed.
+ */
+gnc_numeric gnc_numeric_div(gnc_numeric x, gnc_numeric y, 
                             gint64 denom, gint how);
 /** Negate the argument  */
 gnc_numeric gnc_numeric_neg(gnc_numeric a);