[gcalctool] Fix off-by-one error in mp_cast_to_double

[Robin Sonefors <rsonefors src gnome org>]

commit 19761f8f5ea585cb8818270d0ae3916cb7faf87c
Author: Robin Sonefors <ozamosi flukkost nu>
Date:   Mon Oct 5 07:18:15 2009 +0200

    Fix off-by-one error in mp_cast_to_double

 ChangeLog        |    4 ++++
 src/mp-convert.c |    2 +-
 2 files changed, 5 insertions(+), 1 deletions(-)
---
diff --git a/ChangeLog b/ChangeLog
index 13da6de..9ab8d66 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -7,6 +7,10 @@
 gcalctool change history.
 =========================
 
+2009-10-05 Robin Sonefors <ozamosi flukkost nu>
+
+    * Fix off-by-one in mp_cast_to_double
+
 2009-10-04 Robin Sonefors <ozamosi flukkost nu>
 
     * Make "Insert character" work, use unsigned numbers, and work with UTF-8
diff --git a/src/mp-convert.c b/src/mp-convert.c
index 976e05f..939a946 100644
--- a/src/mp-convert.c
+++ b/src/mp-convert.c
@@ -409,7 +409,7 @@ mp_cast_to_double(const MPNumber *x)
     }
 
     /* NOW ALLOW FOR EXPONENT */
-    ret_val *= mppow_di(db, x->exponent - tm);
+    ret_val *= mppow_di(db, x->exponent - tm - 1);
 
     /* CHECK REASONABLENESS OF RESULT. */
     /* LHS SHOULD BE .LE. 0.5 BUT ALLOW FOR SOME ERROR IN DLOG */