[gnumeric] TDIST: fix x<0 case.

[Morten Welinder <mortenw src gnome org>]

commit 2958d438ca1bb5dfed7a4407c8f3c2a644ed6182
Author: Morten Welinder <terra gnome org>
Date:   Wed Jan 20 15:15:13 2010 -0500

    TDIST: fix x<0 case.

 NEWS                        |    1 +
 plugins/fn-stat/ChangeLog   |    1 +
 plugins/fn-stat/functions.c |    5 ++---
 3 files changed, 4 insertions(+), 3 deletions(-)
---
diff --git a/NEWS b/NEWS
index a6e3a6d..91e6f74 100644
--- a/NEWS
+++ b/NEWS
@@ -2,6 +2,7 @@ Gnumeric 1.9.19
 
 Morten:
 	* Fix TRIMMEAN border case.  [#607562]
+	* Fix TDIST border case.  [#607008]
 
 --------------------------------------------------------------------------
 Gnumeric 1.9.18
diff --git a/plugins/fn-stat/ChangeLog b/plugins/fn-stat/ChangeLog
index 124a331..69d1a39 100644
--- a/plugins/fn-stat/ChangeLog
+++ b/plugins/fn-stat/ChangeLog
@@ -2,6 +2,7 @@
 
 	* functions.c (gnumeric_trimmean): Fix p==1 case.  Return right
 	error value.
+	(gnumeric_tdist): Don't allow negative x.  Fixes #607008.
 
 2010-01-19  Morten Welinder <terra gnome org>
 
diff --git a/plugins/fn-stat/functions.c b/plugins/fn-stat/functions.c
index 7bf9203..b61fc78 100644
--- a/plugins/fn-stat/functions.c
+++ b/plugins/fn-stat/functions.c
@@ -1211,11 +1211,10 @@ gnumeric_tdist (GnmFuncEvalInfo *ei, GnmValue const * const *argv)
 	gnm_float dof = value_get_as_float (argv[1]);
 	int tails = value_get_as_int (argv[2]);
 
-	if (dof < 1 || (tails != 1 && tails != 2))
+	if (x < 0 || dof < 1 || (tails != 1 && tails != 2))
 		return value_new_error_NUM (ei->pos);
 
-	return value_new_float (tails * pt ((tails == 1) ? x : gnm_abs(x),
-					    dof, FALSE, FALSE));
+	return value_new_float (tails * pt (x, dof, FALSE, FALSE));
 }
 
 /***************************************************************************/