[gnumeric] SFTEST: improve extreme-case precision.

[Morten Welinder <mortenw src gnome org>]

commit 67dadcd050019784f20a665569226a1af4721842
Author: Morten Welinder <terra gnome org>
Date:   Fri Jun 11 21:26:38 2010 -0400

    SFTEST: improve extreme-case precision.

 NEWS                        |    2 ++
 plugins/fn-stat/ChangeLog   |    2 ++
 plugins/fn-stat/functions.c |   10 +++++-----
 3 files changed, 9 insertions(+), 5 deletions(-)
---
diff --git a/NEWS b/NEWS
index b3ece5a..4565231 100644
--- a/NEWS
+++ b/NEWS
@@ -32,6 +32,8 @@ Morten:
 	* Mark a sheet dirty when its tab colour is changed.  [#621191]
 	* Fix SERIESSUM issue.
 	* Modernize code for LINEST, LOGEST, and  LOGREG.  [#317426]
+	* GEOMDIST: avoid overflow in extreme cases.
+	* SFTEST: improve extreme-case precision.
 
 --------------------------------------------------------------------------
 Gnumeric 1.10.5
diff --git a/plugins/fn-stat/ChangeLog b/plugins/fn-stat/ChangeLog
index 4a311d7..cbf0b2f 100644
--- a/plugins/fn-stat/ChangeLog
+++ b/plugins/fn-stat/ChangeLog
@@ -5,6 +5,8 @@
 	(gnumeric_linest, gnumeric_logreg, gnumeric_logest): Simplify
 	using gnm_reg_data_collect.  Fixes #317426.
 	(gnumeric_geomdist): Avoid using "int" for "k".
+	(gnumeric_sftest): Avoid using reserved identifier.  Improve
+	precision in extreme cases.
 
 2010-06-10 Andreas J. Guelzow <aguelzow pyrshep ca>
 
diff --git a/plugins/fn-stat/functions.c b/plugins/fn-stat/functions.c
index a3d4655..3de31e4 100644
--- a/plugins/fn-stat/functions.c
+++ b/plugins/fn-stat/functions.c
@@ -4831,7 +4831,7 @@ gnumeric_sftest (GnmFuncEvalInfo *ei, GnmValue const * const *argv)
 				 value_new_error_VALUE (ei->pos));
 	} else {
 		int i;
-		gnm_float stat;
+		gnm_float stat_;
 		gnm_float *ys;
 		gnm_float *zs;
 
@@ -4841,7 +4841,7 @@ gnumeric_sftest (GnmFuncEvalInfo *ei, GnmValue const * const *argv)
 		for (i = 0; i < n; i++)
 			zs[i] = qnorm ((((gnm_float)(i+1))-3./8.)/(n+0.25), 0., 1., TRUE, FALSE);
 
-		if (gnm_range_correl_pop (ys, zs, n, &stat)) {
+		if (gnm_range_correl_pop (ys, zs, n, &stat_)) {
 			value_array_set (result, 0, 0,
 					 value_new_error_VALUE (ei->pos));
 			value_array_set (result, 0, 1,
@@ -4850,17 +4850,17 @@ gnumeric_sftest (GnmFuncEvalInfo *ei, GnmValue const * const *argv)
 			gnm_float p;
 			gnm_float u, v, mu, sig;
 
-			stat = stat * stat;
+			stat_ = stat_ * stat_;
 
 			value_array_set (result, 0, 1,
-					 value_new_float (stat));
+					 value_new_float (stat_));
 
 			u = gnm_log (n);
 			v = gnm_log (u);
 			mu = -1.2725 + 1.0521 * (v - u);
 			sig = 1.0308 - 0.26758 * (v + 2./u);
 
-			p = pnorm (gnm_log (1. - stat), mu, sig, FALSE, FALSE);
+			p = pnorm (gnm_log1p (-stat_), mu, sig, FALSE, FALSE);
 
 			value_array_set (result, 0, 0,
 					 value_new_float (p));