From 9fa3f1d768b7983bef4637908916c784070fd235 Mon Sep 17 00:00:00 2001
From: Morten Welinder <terra@gnome.org>
Date: Sun, 27 May 2018 13:19:31 -0400
Subject: [PATCH] Deriv: cleanups.

---
 plugins/fn-math/functions.c | 31 +++++++++++++++++++++----------
 src/expr-deriv.c            |  8 ++++----
 2 files changed, 25 insertions(+), 14 deletions(-)

diff --git a/plugins/fn-math/functions.c b/plugins/fn-math/functions.c
index 4963c7f53..7a7c7e311 100644
--- a/plugins/fn-math/functions.c
+++ b/plugins/fn-math/functions.c
@@ -1751,16 +1751,17 @@ gnumeric_sumsq (GnmFuncEvalInfo *ei, int argc, GnmExprConstPtr const *argv)
 				     GNM_ERROR_VALUE);
 }
 
+// Construct an equivalend expression
 static GnmExpr const *
-gnumeric_sumsq_deriv (GnmFunc *func,
-		      GnmExpr const *expr, GnmEvalPos const *ep,
+gnumeric_sumsq_equiv (GnmExpr const *expr, GnmEvalPos const *ep,
 		      GnmExprDeriv *info)
 {
-	GnmExprList *l, *args = gnm_expr_deriv_collect (expr, ep, info);
-	GnmExpr const *res;
-	GnmExpr const *sqsum;
-	GnmFunc *fsum = gnm_func_lookup_or_add_placeholder ("SUM");
+	GnmExprList *l, *args;
+	GnmFunc *fsum = gnm_func_lookup ("SUM", NULL);
+
+	if (!fsum) return NULL;
 
+	args = gnm_expr_deriv_collect (expr, ep, info);
 	for (l = args; l; l = l->next) {
 		GnmExpr const *e = l->data;
 		GnmExpr const *ee = gnm_expr_new_binary
@@ -1770,11 +1771,21 @@ gnumeric_sumsq_deriv (GnmFunc *func,
 		l->data = (gpointer)ee;
 	}
 
-	sqsum = gnm_expr_new_funcall (fsum, args);
-	res = gnm_expr_deriv (sqsum, ep, info);
-	gnm_expr_free (sqsum);
+	return gnm_expr_new_funcall (fsum, args);
+}
 
-	return res;
+static GnmExpr const *
+gnumeric_sumsq_deriv (GnmFunc *func,
+		      GnmExpr const *expr, GnmEvalPos const *ep,
+		      GnmExprDeriv *info)
+{
+	GnmExpr const *sqsum = gnumeric_sumsq_equiv (expr, ep, info);
+	if (sqsum) {
+		GnmExpr const *res = gnm_expr_deriv (sqsum, ep, info);
+		gnm_expr_free (sqsum);
+		return res;
+	} else
+		return NULL;
 }
 
 /***************************************************************************/
diff --git a/src/expr-deriv.c b/src/expr-deriv.c
index 981ccbed5..1dcb68f2f 100644
--- a/src/expr-deriv.c
+++ b/src/expr-deriv.c
@@ -552,9 +552,9 @@ gnm_expr_deriv (GnmExpr const *expr,
 	case GNM_EXPR_OP_EXP: {
 		COMMON_BINARY_START
 		GnmFunc *fln = gnm_func_lookup ("ln", NULL);
-		GnmValue const *vb = gnm_expr_get_constant (b);
-		if (vb && VALUE_IS_FLOAT (vb)) {
-			GnmExpr const *bm1 = gnm_expr_new_constant (value_new_float (value_get_as_float (vb) - 1));
+		gnm_float cb;
+		if (is_any_const (b, &cb)) {
+			GnmExpr const *bm1 = gnm_expr_new_constant (value_new_float (cb - 1));
 			GnmExpr const *t1 = mexp (a, 1, bm1, 0);
 			gnm_expr_free (db);
 			return mmul (mmul (b, 1, t1, 0), 0, da, 0);
@@ -575,7 +575,7 @@ gnm_expr_deriv (GnmExpr const *expr,
 	case GNM_EXPR_OP_FUNCALL: {
 		GnmFunc *f = gnm_expr_get_func_def (expr);
 		GnmExpr const *res = gnm_func_derivative (f, expr, ep, info);
-		GnmExpr const *opt = optimize (res);
+		GnmExpr const *opt = res ? optimize (res) : NULL;
 		if (opt) {
 			gnm_expr_free (res);
 			res = opt;
-- 
2.11.4.GIT