[gnumeric] NPER: handler rates (-100%; 0%) too.

[Morten Welinder <mortenw src gnome org>]

commit bfeeface878baf99bd6c210aa19fc0adb557cf9f
Author: Morten Welinder <terra gnome org>
Date:   Tue Jun 9 11:32:00 2009 -0400

    NPER: handler rates (-100%; 0%) too.
---
 NEWS                             |    2 ++
 plugins/fn-financial/ChangeLog   |    7 +++++++
 plugins/fn-financial/functions.c |   12 ++++++++----
 3 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/NEWS b/NEWS
index a7292cd..de09941 100644
--- a/NEWS
+++ b/NEWS
@@ -19,6 +19,8 @@ Morten:
 	* Honour --geometry even when not loading a file.
 	* Fix increase/decrease precision for accounting formats.
 	* Fix array editing criticals.  [#584746]
+	* Fix style problems with operator.xls.  [#585178]
+	* Fix NPER problems.
 
 --------------------------------------------------------------------------
 Gnumeric 1.9.8
diff --git a/plugins/fn-financial/ChangeLog b/plugins/fn-financial/ChangeLog
index cf33a93..57f4c1e 100644
--- a/plugins/fn-financial/ChangeLog
+++ b/plugins/fn-financial/ChangeLog
@@ -1,3 +1,10 @@
+2009-06-09  Morten Welinder  <terra gnome org>
+
+	* functions.c (gnumeric_nper): Negative rates make sense down to,
+	but not including -100%.  Fixes bug reported at
+	http://www.oasis-open.org/committees/download.php/32469/OpenDocument-formula-20090508.odt
+	on page 184.  Hint: there are better places to report problems.
+
 2009-05-23  Morten Welinder <terra gnome org>
 
 	* Release 1.9.8
diff --git a/plugins/fn-financial/functions.c b/plugins/fn-financial/functions.c
index 4565576..dab2934 100644
--- a/plugins/fn-financial/functions.c
+++ b/plugins/fn-financial/functions.c
@@ -2252,11 +2252,15 @@ gnumeric_nper (GnmFuncEvalInfo *ei, GnmValue const * const *argv)
 	gnm_float fv   = argv[3] ? value_get_as_float (argv[3]) : 0;
 	int type       = value_get_paytype (argv[4]);
 
-	if (rate == 0 && pmt != 0)
-		return value_new_float (-(fv + pv) / pmt);
+	if (rate == 0) {
+		if (pmt == 0)
+			return value_new_error_DIV0 (ei->pos);
+		else
+			return value_new_float (-(fv + pv) / pmt);
+	}
 
-	if (rate <= 0.0)
-		return value_new_error_DIV0 (ei->pos);
+	if (rate <= -1)
+		return value_new_error_NUM (ei->pos);
 
 	if (!is_valid_paytype (type))
 		return value_new_error_VALUE (ei->pos);