corrected the division conversion scheme

doc/integer_division.org

@@ -33,13 +33,7 @@ a div_M b = (a - (a mod_M b)) div_C b
 
 * From Euclidian to C
 
-a mod_C b = (a >= 0 ? a mod_M b : - ((-a) mod_M b)) 
-            (using math def to ensure positiveness of remainder))
-          = (a mod_M b) - (a mod_C < 0 ? abs(b) : 0)
-          = a mod_M b - ((a mod_M b <> 0 && a <= 0) ? abs(b) : 0)
-            (using the def of mod_M above)
+a mod_C b = a mod_M b - ((a mod_M b <> 0 && a <= 0) ? abs(b) : 0)
 
 a div_C b = (a - (a mod_C b)) div_M b
-          
-Let's choose the second, simpler, def of mod_C
-
+          = (a mod_M b <> 0 && a <= 0)?((a - a mod_M b + abs(b)) div_M b) :((a - a mod_M b) div_M b)