[gnumeric] lpsolve: improve consistency.

[Morten Welinder <mortenw src gnome org>]

commit fa860deb92782ccb9e92e5226aa77073129fbad1
Author: Morten Welinder <terra gnome org>
Date:   Wed Nov 11 15:54:30 2009 -0500

    lpsolve: improve consistency.

 plugins/lpsolve/ChangeLog       |    5 ++++
 plugins/lpsolve/lpsolve-write.c |   49 +++++++++++++++++++++++++++------------
 2 files changed, 39 insertions(+), 15 deletions(-)
---
diff --git a/plugins/lpsolve/ChangeLog b/plugins/lpsolve/ChangeLog
index ea665bc..7f7db90 100644
--- a/plugins/lpsolve/ChangeLog
+++ b/plugins/lpsolve/ChangeLog
@@ -1,3 +1,8 @@
+2009-11-11  Morten Welinder  <terra gnome org>
+
+	* lpsolve-write.c (lpsolve_affine_func): Zero all input cells
+	initially to ensure consistent results.
+
 2009-11-06  Morten Welinder  <terra gnome org>
 
 	* lpsolve-write.c (lpsolve_file_save): Add progress reporting.
diff --git a/plugins/lpsolve/lpsolve-write.c b/plugins/lpsolve/lpsolve-write.c
index aa26e66..aae3d53 100644
--- a/plugins/lpsolve/lpsolve-write.c
+++ b/plugins/lpsolve/lpsolve-write.c
@@ -40,22 +40,18 @@ gnm_solver_get_lp_coeff (GnmCell *target, GnmCell *cell,
 			 gnm_float *x, GError **err)
 {
         gnm_float x0, x1;
-	GnmValue *old = value_dup (cell->value);
 	gboolean res = FALSE;
 
-	gnm_cell_set_value (cell, value_new_float (1));
-	cell_queue_recalc (cell);
-	gnm_cell_eval (target);
 	if (!VALUE_IS_NUMBER (target->value))
 		goto fail;
-	x1 = value_get_as_float (target->value);
+	x0 = value_get_as_float (target->value);
 
-	gnm_cell_set_value (cell, value_new_float (0));
+	gnm_cell_set_value (cell, value_new_float (1));
 	cell_queue_recalc (cell);
 	gnm_cell_eval (target);
 	if (!VALUE_IS_NUMBER (target->value))
 		goto fail;
-	x0 = value_get_as_float (target->value);
+	x1 = value_get_as_float (target->value);
 
 	*x = x1 - x0;
 	res = TRUE;
@@ -69,7 +65,7 @@ fail:
 	*x = 0;
 
 out:
-	gnm_cell_set_value (cell, old);
+	gnm_cell_set_value (cell, value_new_int (0));
 	cell_queue_recalc (cell);
 	gnm_cell_eval (target);
 
@@ -90,21 +86,33 @@ static gboolean
 lpsolve_affine_func (GString *dst, GnmCell *target,
 		     GSList *input_cells, GError **err)
 {
-	GSList *l;
+	GSList *l, *ol;
 	gboolean any = FALSE;
-	gnm_float y = value_get_as_float (target->value);
+	gnm_float y;
+	GSList *old_values = NULL;
+	gboolean ok = TRUE;
+
+ 	for (l = input_cells; l; l = l->next) {
+	        GnmCell *cell = l->data;
+		old_values = g_slist_prepend (old_values,
+					      value_dup (cell->value));
+		gnm_cell_set_value (cell, value_new_int (0));
+		cell_queue_recalc (cell);
+	}
+	old_values = g_slist_reverse (old_values);
+
+	gnm_cell_eval (target);
+	y = value_get_as_float (target->value);
 
  	for (l = input_cells; l; l = l->next) {
 	        GnmCell *cell = l->data;
 		gnm_float x;
-		gboolean ok = gnm_solver_get_lp_coeff (target, cell, &x, err);
+		ok = gnm_solver_get_lp_coeff (target, cell, &x, err);
 		if (!ok)
-			return FALSE;
+			goto fail;
 		if (x == 0)
 			continue;
 
-		y -= x * value_get_as_float (cell->value);
-
 		if (any) {
 			if (x < 0)
 				g_string_append (dst, " - ");
@@ -129,7 +137,18 @@ lpsolve_affine_func (GString *dst, GnmCell *target,
 	if (!any || y)
 		gnm_string_add_number (dst, y);
 
-	return TRUE;
+fail:
+ 	for (l = input_cells, ol = old_values;
+	     l;
+	     l = l->next, ol = ol->next) {
+	        GnmCell *cell = l->data;
+		GnmValue *old = ol->data;
+		gnm_cell_set_value (cell, old);
+		cell_queue_recalc (cell);
+	}
+	g_slist_free (old_values);
+
+	return ok;
 }
 
 static GString *