From: "Christopher Allen" Subject: Re: [DGD] SkotOS 2.0 Date: Tue, 31 Aug 2004 12:40:32 -0700 Par Winzell wrote: > It's not interpreted in LPC. Merry is compiled into actual LPC. There > is no significant speed loss. The benefits are not so much in the > language itself but in the fact that it allows little snippets of > code to be sent around as data, which is a natural way for us to hook > logic onto events. The name Merry comes from "Mediated Execution Registry Involving A = Dialect Of C" -- which although somewhat a joke because it is the = successor of Bilbo "Built In Language Between Object", but the acronym = that Merry stands for actually does describe it well. The key is the the "mediated" part -- this means that Merry is somewhat = sandboxed -- not to the scale that Java is, but helpful. For instance, = in Merry code we try to ensure that Merry scripts inside game objects = only interact with objects that involve the virtual game world, not = random other objects it has no business with. Only a limited number of = functions can be called from Merry, and even then they are only allowed = implicitly, like fetching/setting properties, Act(), etc. File system = access is completely disabled, as well as things like starting things up = or shutting down processes, and some communications functions. In addition, the langage is run through a complex parse_string() = grammar, which gives us the ability to add some useful synatactic sugar = additions: constants, per-thread global $variables, $foo: = function-parameters, you can directly access the property database for = values through ${someobject}.property:name, and a few other useful = things like the ability to do inline SAM (Skotos Active Markup) with = $"{oneof:one|two|three}". Independent of the Merry language itself, there are a large variety of = useful game specific functions, such as EmitTo(), EmitIn(), Set(), etc. Here is a small code example. A simple torch, which responds (i.e. the = "react-") to the signal (what might be called an event) named = "react-post:light-dob". This signal is sent to a direct object (i.e. = -dob) immediately after (i.e. -post) a verb is used that might turn on a = light in an object (such as the verbs light, ignite, etc.): /* Standard Flame Scripts */ =20 /* react-post:light-dob */ =20 /* Example by ChristopherA */ =20 =20 /* If flame-on was set during the reaction, turn trait:flame on */ =20 /* and let setprop-post:trait:flame handle cleaning things up. */ =20 /* Note: we do this in react-post so that things look clean */ =20 /* during normal processing of the react:light-dob signal, */ =20 /* e.g. you don't get the result "You light the flaming torch." */ =20 /* when it isn't actually flaming yet. */ = if ( Get(this,"trait:flame-on") ){ =20 Set( this, "trait:flame", TRUE); =20 Set( this, "trait:flame-on", FALSE);=20 /* Now show everyone that a flame has appeared. */ = =20 EmitTo ($actor, "The top of " + Describe($this, $actor, $actor) + = " crackles alight.\n"); =20 EmitIn(Get($actor, "base:environment"), "The top of " + = Describe($this) + " crackles alight.\n", $actor);=20 } =20 =20 /* This is a react-post, so no need to return TRUE; */Note the = $actor, $this -- these are per-thread global variables passed to this = script. They will be the same for all the signals that were initially = caused by the first "light my torch" verb. Next we have a signal that is sent to objects if a property is changed, = called setprop-post. An example of use is when the torch is lit -- = either someone interacted with the torch directly (for instance "light = my torch" above) or something else lit it (put my torch in fireplace) -- = either way, the trait:flame property is set to true and = setprop-post:trait:flame is sent to the object. /* Standard Flame Scripts */ /* setprop-post:trait:flame */ /* Example by ChristopherA */ if ($(hook-property) !=3D "trait:flame") return TRUE; /* If a flame exists... */ if ( Get(this,"trait:flame") ){ /* reveal the flame and change adjectives on the prime detail */ Set( this, "details:flame:hidden", FALSE); Set( this, "details:smoke:hidden", FALSE); Set( this, "details:default:adjectives:flaming", TRUE); Set( this, "details:default:adjectives:lit", TRUE); Set( this, "details:default:adjectives:unlit", FALSE); /* if the torch has never been flamed before, scorch it. */ if ( ! (Get(this,"trait:flame:remains")) ) { Set(this, "trait:flame:remains", "It is slightly scorched."); } /* Now start the timer which will tick ever 90 seconds */ Set(this, "trait:flame:tick_id", Every("tick", 90)); } /* ... if a flame does not exist, then hide the flame and */ /* change adjectives on the prime detail. */ else { Set( this, "details:flame:hidden", TRUE); Set( this, "details:smoke:hidden", TRUE); Set( this, "details:default:adjectives:flaming", FALSE); Set( this, "details:default:adjectives:lit", FALSE); Set( this, "details:default:adjectives:unlit", TRUE); /* Now turn of the timer, so it will not tick. */ Stop(Get(this, "trait:flame:tick_id")); } /* This is a setprop-post, so no need to return TRUE; */Finally, we = need a way to emit messages periodically as the torch is burning, and to = destroy the torch when it is used up: /* Standard Flame Scripts */=20 /* timer:tick */=20 /* Example by ChristopherA */=20 =20 /* timer:tick is called every X seconds (typically 60 or */=20 /* 90 seconds) as set up in the Every() function in */=20 /* the setprop-post:trait:flame merry script. */=20 =20 object env; object act; int tick;=20 =20 /* We've been triggered, so increment our tick count */=20 tick =3D Get(this, "trait:flame:tick_cnt") + 1;=20 Set(this, "trait:flame:tick_cnt", tick);=20 =20 /* set some variables because timer:tick exists in an */=20 /* an environment where there are very few arguments */=20 /* and you can't rely on where the item. It could be */=20 /* on the floor, in someones bag in the nil, or in */=20 /* the hands of the person who lit it. */=20 =20 /* If we are being held, we want our environment output */=20 /* to be in the room of the person who is holding us. */ if (env =3D Get(this, "base:environment")) {=20 env =3D Get(env, "base:environment");=20 }=20 =20 /* If we are being held, we want our actor output */=20 /* to be the person holding us, or the room if the item */=20 /* has been dropped. */ act =3D this."base:environment";=20 if (act."base:environment") {=20 /* actor has an environment, all is well */=20 env =3D act."base:environment";=20 } else {=20 /* if act has no environment, we've been dropped and act =3D env! = */=20 env =3D act;=20 act =3D nil;=20 }=20 =20 /* For each tick, do different things... */=20 =20 /* ...partially burn out the item */=20 if (tick =3D=3D 5) {=20 Set(this, "trait:flame:remains", "It is about half burned out");=20 }=20 /* ...mostly burn out the item */=20 if (tick =3D=3D 10) {=20 Set(this, "trait:flame:remains", "It is almost burned out.");=20 }=20 /* ...complete burn out the item */=20 if (tick >=3D 12) {=20 if ( act !=3D nil ) {=20 EmitTo(act, Describe(this, nil, act) + " sputters out.\n");=20 }=20 if(this."base:environment") {=20 EmitIn(env, Describe(this, nil, nil) + " sputters out.\n", = act);=20 }=20 Set(this, "trait:flame", FALSE);=20 Set(this, "trait:flame:flammable", FALSE);=20 Set(this, "trait:flame:remains", "It is completely burned out.");=20 Set( this, "details:default:adjectives:spent", TRUE);=20 /* stop us from ticking anymore */=20 Stop(Get(this, "trait:flame:tick_id"));=20 =20 /* Now return false, but set up a delay so that */=20 /* this object can decay in 86400 seconds (1 day) */=20 $delay(86400, FALSE, "4a8d");=20 =20 /* We have to re-establish our local variables, as */=20 /* they are incorrect after a delay. */=20 Set(this, "trait:flame:tick_cnt", tick);=20 if (env =3D Get(this, "base:environment")) {=20 env =3D Get(env, "base:environment");=20 }=20 act =3D this."base:environment";=20 if (act."base:environment") {=20 env =3D act."base:environment";=20 } else {=20 env =3D act;=20 act =3D nil;=20 }=20 =20 /* If we are not in the nil, then tell people that */=20 /* we are disintegrating... */=20 if ( act !=3D nil ) {=20 EmitTo(act, Describe(this, nil, act) + " disintegrates from = age.\n");=20 }=20 if (this."base:environment") {=20 EmitIn(env, Describe(this, nil, nil) + " disintegrates from = age.\n", act);=20 }=20 /* Ok, we are done. Bye. */=20 Slay(this);=20 return FALSE;=20 }=20 =20 /* For every tick, there is a 30% chance of a random emit*/=20 switch(random(10)) {=20 /* Again, if we are not in the nil, do the emits */=20 case 0: {=20 if ( act !=3D nil ) {=20 EmitTo(act, "A trail of smoke wisps upwards through the = air from " + Describe(this, nil, act) + ".\n");=20 }=20 if(this."base:environment") {=20 EmitIn(env, "A trail of smoke wisps upwards through the air = from " + Describe(this, nil, nil) + ".\n", act);=20 }=20 } break;=20 case 1: {=20 if(this."base:environment") {=20 EmitTo(act, "There is a quiet fizzle of hot oil from " + = Describe(this, nil, act) + ".\n");=20 }=20 if(this."base:environment") {=20 EmitIn(env, "There is a quiet fizzle of hot oil from " + = Describe(this, nil, nil) + ".\n", act);=20 }=20 } break;=20 case 2: {=20 if(this."base:environment") {=20 EmitTo(act, capitalize(Describe(this, nil, act) + " = flickers.\n"));=20 }=20 if(this."base:environment") {=20 EmitIn(env, capitalize(Describe(this, nil, nil) + " = flickers.\n"), act);=20 }=20 } break; default: break; } The above is only three of about 8 different Merry scripts used by = torches. -- Christopher Allen ------------------------------------------------------------------------ .. Christopher Allen Skotos Tech Inc. .. .. 2342 Shattuck Ave Ste #512, Berkeley, CA 94704-1517 .. .. www.skotos.net www.rpg.net o510/647-2760 f510/849-1717 ..