diff --git a/Nasal/contrail.nas b/Nasal/contrail.nas
index c9e93572c..2673deb1e 100644
--- a/Nasal/contrail.nas
+++ b/Nasal/contrail.nas
@@ -16,12 +16,12 @@ updateContrail = func{
     contrail_temp_Node.setValue(con_temp);
 
     if (y < con_temp and y < -40){
-            contrail_Node.setValue(1);
-        } else {
-            contrail_Node.setValue(0);
-        }
+        contrail_Node.setValue(1);
+    } else {
+        contrail_Node.setValue(0);
+    }
 
-        settimer(updateContrail,30)
+    settimer(updateContrail,30)
 }
 
 ### Contrail
diff --git a/Nasal/controls.nas b/Nasal/controls.nas
index 40abd7946..4ef317279 100644
--- a/Nasal/controls.nas
+++ b/Nasal/controls.nas
@@ -196,10 +196,9 @@ var stepSlats = func(step) {
 # magnetos, for instance), work similarly but not compatibly, and
 # could be integrated.
 #
-var stepProps = func {
-    var dst = props.globals.getNode(arg[0]);
-    var array = props.globals.getNode(arg[1]);
-    var delta = arg[2];
+var stepProps = func(dst, array, delta) {
+    dst = props.globals.getNode(dst);
+    array = props.globals.getNode(array);
     if(dst == nil or array == nil) { return; }
 
     var sets = array.getChildren("setting");
@@ -238,30 +237,30 @@ var TRIM_RATE = 0.045;
 # events.  They are *not* good for binding to the keyboard, since (at
 # least) X11 synthesizes its own key repeats.
 #
-var elevatorTrim = func {
-    slewProp("/controls/flight/elevator-trim", arg[0] * TRIM_RATE); }
-var aileronTrim = func {
-    slewProp("/controls/flight/aileron-trim", arg[0] * TRIM_RATE); }
-var rudderTrim = func {
-    slewProp("/controls/flight/rudder-trim", arg[0] * TRIM_RATE); }
+var elevatorTrim = func(speed) {
+    slewProp("/controls/flight/elevator-trim", speed * TRIM_RATE); }
+var aileronTrim = func(speed) {
+    slewProp("/controls/flight/aileron-trim", speed * TRIM_RATE); }
+var rudderTrim = func(speed) {
+    slewProp("/controls/flight/rudder-trim", speed * TRIM_RATE); }
 
 var THROTTLE_RATE = 0.33;
 
-var adjThrottle = func {
-    adjEngControl("throttle", arg[0]); }
-var adjMixture = func {
-    adjEngControl("mixture", arg[0]); }
-var adjCondition = func {
-    adjEngControl("condition", arg[0]); }
-var adjPropeller = func {
-    adjEngControl("propeller-pitch", arg[0]); }
+var adjThrottle = func(speed) {
+    adjEngControl("throttle", speed); }
+var adjMixture = func(speed) {
+    adjEngControl("mixture", speed); }
+var adjCondition = func(speed) {
+    adjEngControl("condition", speed); }
+var adjPropeller = func(speed) {
+    adjEngControl("propeller-pitch", speed); }
 
-var adjEngControl = func {
-    var delta = arg[1] * THROTTLE_RATE * getprop("/sim/time/delta-realtime-sec");
+var adjEngControl = func(prop, speed) {
+    var delta = speed * THROTTLE_RATE * getprop("/sim/time/delta-realtime-sec");
     var (value, count) = (0, 0);
     foreach(var e; engines) {
         if(e.selected.getValue()) {
-            var node = e.controls.getNode(arg[0], 1);
+            var node = e.controls.getNode(prop, 1);
             node.setValue(node.getValue() + delta);
             value += node.getValue(); # must read again because of clamping
             count += 1;
diff --git a/Nasal/gui.nas b/Nasal/gui.nas
index bc92139bd..b0e0831a1 100644
--- a/Nasal/gui.nas
+++ b/Nasal/gui.nas
@@ -242,11 +242,10 @@ var currTimer = 0;
 # API.  Note especially the slightly tricky addChild() method.
 #
 var Widget = {
-    set : func { me.node.getNode(arg[0], 1).setValue(arg[1]); },
+    set : func(name, val) { me.node.getNode(name, 1).setValue(val); },
     prop : func { return me.node; },
     new : func { return { parents : [Widget], node : props.Node.new() } },
-    addChild : func {
-        var type = arg[0];
+    addChild : func(type) {
         var idx = size(me.node.getChildren(type));
         var name = type ~ "[" ~ idx ~ "]";
         var newnode = me.node.getNode(name, 1);
@@ -1134,9 +1133,9 @@ var showWeightDialog = func {
 #     </text>
 # </help>
 #
-var showHelpDialog = func {
-    var node = props.globals.getNode(arg[0]);
-    if (arg[0] == "/sim/help" and size(node.getChildren()) < 4) {
+var showHelpDialog = func(path, toggle=0) {
+    var node = props.globals.getNode(path);
+    if (path == "/sim/help" and size(node.getChildren()) < 4) {
         node = node.getChild("common");
     }
 
@@ -1147,7 +1146,7 @@ var showHelpDialog = func {
             name = getprop("/sim/aircraft");
         }
     }
-    var toggle = size(arg) > 1 and arg[1] != nil and arg[1] > 0;
+    var toggle = toggle > 0;
     if (toggle and contains(dialog, name)) {
         fgcommand("dialog-close", props.Node.new({ "dialog-name": name }));
         delete(dialog, name);
diff --git a/Nasal/material.nas b/Nasal/material.nas
index 1b3dab713..d4ad8d631 100644
--- a/Nasal/material.nas
+++ b/Nasal/material.nas
@@ -50,17 +50,14 @@
 
 var dialog = nil;
 
-var colorgroup = func {
-	var parent = arg[0];  # pui parent
-	var name = arg[1];    # "diffuse"
-	var base = arg[2];
-	var undef = func { props.globals.getNode(base ~ name ~ "/" ~ arg[0]) == nil };
+var colorgroup = func(parent, name, base) {
+	var undef = func { props.globals.getNode(base ~ name ~ "/" ~ parent) == nil };
 
 	if (undef("red") and undef("green") and undef("blue")) {
 		return 0;
 	}
 
-	if (arg[3] != nil) {
+	if (base != nil) {
 		parent.addChild("hrule").setColor(1, 1, 1, 0.5);
 	}
 
@@ -76,11 +73,7 @@ var colorgroup = func {
 }
 
 
-var mat = func {
-	var parent = arg[0];
-	var name = arg[1];
-	var path = arg[2];
-	var format = arg[3];
+var mat = func(parent, name, path, format, min=nil, max=nil) {
 	if (props.globals.getNode(path) != nil) {
 		var grp = parent.addChild("group");
 		grp.set("layout", "hbox");
@@ -91,9 +84,9 @@ var mat = func {
 		var slider = grp.addChild("slider");
 		slider.set("property", path);
 		slider.set("live", 1);
-		if (size(arg) == 6) {
-			slider.set("min", arg[4]);
-			slider.set("max", arg[5]);
+		if (min != nil and max != nil) {
+			slider.set("min", min);
+			slider.set("max", max);
 		}
 		slider.setBinding("dialog-apply");
 
@@ -107,8 +100,7 @@ var mat = func {
 }
 
 
-var showDialog = func {
-	var base = arg[0];
+var showDialog = func(base, title=nil, x=nil, y=nil) {
 	while (size(base) and substr(base, size(base) - 1, 1) == "/") {
 		base = substr(base, 0, size(base) - 1);
 	}
@@ -121,14 +113,14 @@ var showDialog = func {
 		parentdir = c ~ parentdir;
 	}
 
-	var title = if (size(arg) > 1 and arg[1] != nil) { arg[1] } else { parentdir };
+	if (title == nil) var title = parentdir;
 	var name = "material-" ~ parentdir;
 	base = base ~ "/";
 
 	dialog = gui.Widget.new();
 	dialog.set("name", name);
-	if (size(arg) > 2 and arg[2] != nil) { dialog.set("x", arg[2]) }
-	if (size(arg) > 3 and arg[3] != nil) { dialog.set("y", arg[3]) }
+	if (x != nil) dialog.set("x", x);
+	if (y != nil) dialog.set("y", y);
 	dialog.set("layout", "vbox");
 
 	var titlebar = dialog.addChild("group");
@@ -152,7 +144,7 @@ var showDialog = func {
 	h += colorgroup(dialog, "emission", base, h);
 	h += colorgroup(dialog, "specular", base, h);
 
-	var undef = func { props.globals.getNode(base ~ arg[0]) == nil };
+	var undef = func(prop) { props.globals.getNode(base ~ prop) == nil };
 	if (!(undef("shininess") and undef("transparency/alpha") and undef("threshold"))) {
 		if (h) {
 			dialog.addChild("hrule").setColor(1, 1, 1, 0.5);