diff --git a/expr.c b/expr.c
index abdd236..19aca0c 100644
--- a/expr.c
+++ b/expr.c
@@ -1,8 +1,8 @@
 /*
  * expr.c - Expressions and values
  *
- * Written 2009 by Werner Almesberger
- * Copyright 2009 by Werner Almesberger
+ * Written 2009, 2010 by Werner Almesberger
+ * Copyright 2009, 2010 by Werner Almesberger
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -41,39 +41,35 @@ void fail_expr(const struct expr *expr)
 /* ----- unit conversion --------------------------------------------------- */
 
 
+/*
+ * If an expression contains a typo, we may get large exponents. Thus, we just
+ * "sprintf" in order to be able to handle any integer. Since the number of
+ * different exponents in a session will still be small, we use "unique" to
+ * give us a constant string, so that we don't have to worry about memory
+ * allocation.
+ */
+
 const char *str_unit(struct num n)
 {
+	const char *unit;
+	char buf[20]; /* @@@ plenty */
+
 	if (n.exponent == 0)
-		return "";
-	if (n.type == nt_mm) {
-		switch (n.exponent) {
-		case -2:
-			return "mm^-2";
-		case -1:
-			return "mm^-1";
-		case 1:
-			return "mm";
-		case 2:
-			return "mm^2";
-		default:
-			abort();
-		}
+		return stralloc("");
+	switch (n.type) {
+	case nt_mm:
+		unit = "mm";
+		break;
+	case nt_mil:
+		unit = "mil";
+		break;
+	default:
+		abort();
 	}
-	if (n.type == nt_mil) {
-		switch (n.exponent) {
-		case -2:
-			return "mil^(-2)";
-		case -1:
-			return "mil^(-1)";
-		case 1:
-			return "mil";
-		case 2:
-			return "mil^2";
-		default:
-			abort();
-		}
-	}
-	abort();
+	if (n.exponent == 1)
+		return unit;
+	sprintf(buf, "%s^%d", unit, n.exponent);
+	return unique(buf);
 }
 
 
@@ -115,6 +111,14 @@ struct num op_num(const struct expr *self, const struct frame *frame)
 }
 
 
+/*
+ * We have two modes of operation: during instantiation and editing, after
+ * instantiation. During instantiation, we follow curr_row and curr_parent.
+ * These pointers are NULL when instantiation finishes, and we use this as a
+ * signal that we're now in editing mode. In editing mode, the "active" values
+ * are used instead of the "current" ones.
+ */
+
 struct num eval_var(const struct frame *frame, const char *name)
 {
 	const struct table *table;
@@ -124,7 +128,8 @@ struct num eval_var(const struct frame *frame, const char *name)
 	struct num res;
 
 	for (table = frame->tables; table; table = table->next) {
-		value = table->curr_row->values;
+		value = table->curr_row ? table->curr_row->values :
+		    table->active_row->values;
 		for (var = table->vars; var; var = var->next) {
 			if (var->name == name) {
 				if (var->visited) {
@@ -143,6 +148,8 @@ struct num eval_var(const struct frame *frame, const char *name)
 	}
 	for (loop = frame->loops; loop; loop = loop->next)
 		if (loop->var.name == name) {
+			if (loop->curr_value == UNDEF)
+				return make_num(loop->n+loop->active);
 			if (!loop->initialized) {
 				fail("uninitialized loop \"%s\"", name);
 				return undef;
@@ -151,6 +158,8 @@ struct num eval_var(const struct frame *frame, const char *name)
 		}
 	if (frame->curr_parent)
 		return eval_var(frame->curr_parent, name);
+	if (frame->active_ref)
+		return eval_var(frame->active_ref->frame, name);
 	return undef;
 }
 
@@ -164,7 +173,8 @@ static const char *eval_string_var(const struct frame *frame, const char *name)
 	const char *res;
 
 	for (table = frame->tables; table; table = table->next) {
-		value = table->curr_row->values;
+		value = table->curr_row ? table->curr_row->values :
+		    table->active_row->values;
 		for (var = table->vars; var; var = var->next) {
 			if (var->name == name) {
 				if (var->visited)
@@ -183,6 +193,8 @@ static const char *eval_string_var(const struct frame *frame, const char *name)
 			return NULL;
 	if (frame->curr_parent)
 		return eval_string_var(frame->curr_parent, name);
+	if (frame->active_ref)
+		return eval_string_var(frame->active_ref->frame, name);
 	return NULL;
 }
 
diff --git a/gui_frame.c b/gui_frame.c
index aeaecef..ca8ead6 100644
--- a/gui_frame.c
+++ b/gui_frame.c
@@ -535,6 +535,39 @@ static void unselect_var(void *data)
 }
 
 
+static void show_value(const struct expr *expr, const struct frame *frame)
+{
+	const char *value_string;
+	struct num value;
+
+	status_set_type_x(NULL, "value =");
+	value_string = eval_str(expr, frame);
+	if (value_string)
+		status_set_x(NULL, "\"%s\"", value_string);
+	else {
+		value = eval_num(expr, frame);
+		if (is_undef(value))
+			status_set_x(NULL, "undefined");
+		else
+			status_set_x(NULL, "%lg%s", value.n, str_unit(value));
+	}
+}
+
+
+static void show_var_value(const struct var *var, const struct frame *frame)
+{
+	const struct var *walk;
+	const struct value *value;
+
+	if (!var->table)
+		return;
+	value = var->table->active_row->values;
+	for (walk = var->table->vars; walk != var; walk = walk->next)
+		value = value->next;
+	show_value(value->expr, frame);
+}
+
+
 static void edit_var(struct var *var,
     void (*set_values)(void *user, const struct value *values, int n_values),
     void *user, int max_values)
@@ -543,6 +576,7 @@ static void edit_var(struct var *var,
 	label_in_box_bg(var->widget, COLOR_VAR_EDITING);
 	status_set_type_entry(NULL, "name =");
 	status_set_name("Variable name", "%s", var->name);
+	show_var_value(var, var->frame);
 	edit_nothing();
 	edit_unique_with_values(&var->name, validate_var_name, var,
 	    set_values, user, max_values,
@@ -575,21 +609,23 @@ static void unselect_value(void *data)
 }
 
 
-static void edit_value(struct value *value)
+static void edit_value(struct value *value, const struct frame *frame)
 {
 	inst_select_outside(value, unselect_value);
 	label_in_box_bg(value->widget, COLOR_EXPR_EDITING);
+	show_value(value->expr, frame);
 	edit_nothing();
 	edit_expr(&value->expr, "Value");
 }
 
 
-static void edit_value_list(struct value *value,
+static void edit_value_list(struct value *value, const struct frame *frame,
     void (*set_values)(void *user, const struct value *values, int n_values),
     void *user)
 {
 	inst_select_outside(value, unselect_value);
 	label_in_box_bg(value->widget, COLOR_VAR_EDITING);
+	show_value(value->expr, frame);
 	edit_nothing();
 	edit_expr_list(value->expr, set_values, user, "Value(s)");
 }
@@ -674,7 +710,7 @@ static gboolean assignment_value_select_event(GtkWidget *widget,
 	switch (event->button) {
 	case 1:
 		edit_nothing();
-		edit_value(value);
+		edit_value(value, value->row->table->vars->frame);
 		break;
 	}
 	return TRUE;
@@ -797,7 +833,8 @@ static gboolean table_value_select_event(GtkWidget *widget,
 		if (!value->row ||
 		    value->row->table->active_row == value->row) {
 			edit_nothing();
-			edit_value_list(value, set_row_values, value);
+			edit_value_list(value, value->row->table->vars->frame,
+			    set_row_values, value);
 		} else {
 			select_row(value->row);
 			change_world();
@@ -969,7 +1006,7 @@ static gboolean loop_from_select_event(GtkWidget *widget,
 	switch (event->button) {
 	case 1:
 		edit_nothing();
-		edit_value(&loop->from);
+		edit_value(&loop->from, loop->var.frame);
 		break;
 	}
 	return TRUE;
@@ -984,7 +1021,7 @@ static gboolean loop_to_select_event(GtkWidget *widget,
 	switch (event->button) {
 	case 1:
 		edit_nothing();
-		edit_value(&loop->to);
+		edit_value(&loop->to, loop->var.frame);
 		break;
 	}
 	return TRUE;
diff --git a/obj.c b/obj.c
index abc70ff..88514f1 100644
--- a/obj.c
+++ b/obj.c
@@ -1,8 +1,8 @@
 /*
  * obj.c - Object definition model
  *
- * Written 2009 by Werner Almesberger
- * Copyright 2009 by Werner Almesberger
+ * Written 2009, 2010 by Werner Almesberger
+ * Copyright 2009, 2010 by Werner Almesberger
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -239,6 +239,7 @@ static int run_loops(struct frame *frame, struct loop *loop,
 		n++;
 	}
 	loop->initialized = 0;
+	loop->curr_value = UNDEF;
 	if (active) {
 		loop->n = from.n;
 		loop->iterations = n;
@@ -279,6 +280,7 @@ static int generate_frame(struct frame *frame, struct coord base,
 	frame->curr_parent = parent;
 	ok = iterate_tables(frame, frame->tables, base, active);
 	inst_end_frame(frame);
+	frame->curr_parent = NULL;
 	return ok;
 }