added lemma divAlg_div_mof

--- a/src/HOL/Integ/IntDiv.thy	Mon May 21 19:11:39 2007 +0200
+++ b/src/HOL/Integ/IntDiv.thy	Mon May 21 19:11:40 2007 +0200
@@ -68,6 +68,10 @@
   div_def: "a div b == fst (divAlg (a, b))"
   mod_def: "a mod b == snd (divAlg (a, b))" ..
 
+lemma divAlg_mod_div:
+  "divAlg (p, q) = (p div q, p mod q)"
+  by (auto simp add: div_def mod_def)
+
 text{*
 Here is the division algorithm in ML: