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== Spell language
* Comments: One-line comments using '#' or '//' as prefix
* names vs. invocations: spells and anchors have both names
and invocations. Names are used to refer to spells and
anchors from within scripts without revealing their
invocations.
Each spell specification file consists of a sequence of definitions of
globals, anchors, spells, and procedures.
Types:
------
These are the primitive types:
* int
* string
* dir (a direction: N, S, SE, NW etc.)
* location (a single spot in the world)
* entity (a PC, NPC, or monster)
* area (a set of locations)
* spell (a spell)
* invocation (a spell instance)
* fail (a separate type that arises implicitly when a function
fails)
`fail' arises in special circumstances in some functions, e.g. when
trying to divide by zero, or when function parameters fail to
type-check. When a fail value flows into an operation, than that
operation is skipped. When a fail value flows into a function, then
that function evaluates to fail, except for
* if_then_else (which permits `fail' in its true or false branch)
* failed (which returns true iff the argument is of type fail).
We will use standard functional type notation:
`int * string -> entity' denotes the type of a function that accepts
an integer and a string and returns an entity. We use the return `()'
for operations (which return nothing).
Globals:
--------
A `global' is a global variable, declared and defined in the
same line:
foo = "this is a string";
Expressions can be arbitrary language expressions. Note that globals
can only reference the values of globals defined earlier in the same
program.
There are two special globals:
* min_casttime : int
Minimal number of milliseconds of cast delay, no matter what any
given spell may say. Cast delay is the time before the next spell
can be cast.
* obscure : int
Chance of a character of a given spell to be obscured (masked out
by an asterisk).
Globals can also be defined as CONST (though this should not be done
for the special globals listed above or they will not take effect.)
CONST-defined globals cannot be re-defined.
Expressions:
------------
Expressions occur in globals, anchors, spells, and procedures.
Expressions evaluate to values of a given type. Expressions can be
simple literals, area literals, infix expressions, function
applications, or variable refecences.
- Simple literals:
* 42, 0xff: int literals
* N, S, E, W, NE, NW, SE, SW : dir literals
* "foo bar" : string literals
- Area literals:
* @("new_3-1.gat", 26, 26)
This area denotes a single field on a map (new_3-1.gat,
co-ordinates (26,26).
* @("new_3-1.gat", 26, 26) @+ (10, 10)
This area is 100 fields, stretching to a field of size 10x10 to
the south and east of (26,26) in new_3-1.gat.
* @("new_3-1.gat", 26, 26) towards S (5, 3)
This area is a rectangular field of depth 3 and width 5 to the
south of (26,26) in new_3-1.gat. `depth 3' here means that it
stretches three fields to the south. `width 5' here means that it
extends five fields to the east and five to the west of the
specified coordinate, for a total width of 11.
The only directions supported here are S, E, N, W.
- Infix expressions:
Infix expressions are special functions in which the operator is
written between two expressions. Infix expressions largely follow
the C precedence rules. The following infix operators are
supported:
* addition (+) (operates on ints, concatenates strings, and
constructs the union of areas)
* subtraction (- : int * int -> int)
* multiplication (* : int * int -> int)
* division (/ : int * int -> int, may fail)
* modulo (% : int * int -> int, may fail)
* comparison (<, >, >=, <=, =, <> : int * int -> int)
Comparison operators generally work on ints and strings.
(In)equality checks work on all values except for areas.
Note that "==" and "!=" are available as alternatives for "=" and
"<>" (respectively).
* conjunction and disjunction (&&, || : int * int -> int). Note
that these are not short-circuit.
* Bitwise or (| : int * int -> int)
* Bitwise and (& : int * int -> int)
* Bitwise xor (^ : int * int -> int)
* Shift left and right (<<, >> : int * int -> int)
- Function applications:
Function applications are written as
f(arg1, ..., argn)
where each `argi' is an arbitrary expression.
For a complete list of Functions, see `functions' below.
- Variable references:
The expression (foo + 1) references a variable `foo' which must have
been previously defined.
Anchors:
--------
Anchors are teleport anchors; spells can look them up by name. Each
teleport anchor is written as
TELEPORT-ANCHOR <id> : <invocation-string> = <location>
For example:
TELEPORT-ANCHOR tulimshar : "home" = @("new_3-1.gat", 26, 26) @+(10, 10)
This maps the teleport anchor `tulimshar' to an area in new_3-1.gat
binds it to the name "home". The function `anchor' can look up
teleport anchors (cf. the function library).
Spells:
-------
Each spell is written either as
[spell-modifiers] SPELL <id> : <name> = <spelldef>
or as
[spell-modifiers] SPELL <id> (<id> : <sty>) : <name> = <spelldef>
For example,
SPELL random_dance : "zxr" = ...
creates a spell `random_dance' and makes it available under the
invocation "zxr". The string `...' is not a valid <spelldef>; we will
look at proper spelldefs below. An alternative example illustrates
the use of parameters:
SPELL shout (message : STRING) : "zzx" = ...
This defines a spell `shout' (bound to invocation "zzx") that takes
a parameter `message' of type STRING. Valid types are STRING and PC:
PC parameters are automatically translated into a player character
entity of that name, or mapped to the caster if the specified name
does not map to a player character or is missing.
The list of spell modifiers is short:
* SILENT means that the spell's invocation will never be broadcast,
not even obscured.
* LOCAL means that the spell is bound to the location it was cast at
and will not `travel' with the caster.
* NONMAGIC means that the spell is not affected by the caster's ability
to perform magic. Typically used for special (quest) keywords.
Modifiers may be given in any order, but only once.
- Spell bodies
Spell bodies consist of three parts: LET bindings, spell guards and
effects. LET bindings locally bind names to values. Spell guards
are constraints that must be satisfied for the spell to be
triggered. Effects describes what happens if the spell is
successfully triggered. Spells may have multiple guards and
effects.
Consider the following example:
SPELL plugh (message : STRING) : "zzx" =
LET x = "kappa"
y = "sigma"
IN
(MANA 1, CATALYSTS ["Pearl"]) => EFFECT message (caster, "First branch");
| (MANA 20) => EFFECT message (caster, "Second branch")
This defines a spell `plugh' with two let bindings (`x' bound to
"kappa" and `y' bound to "sigma") and two `branches' which are
tested in sequence. The first branch tests whether the caster has
one spellpoint and owns a pearl-- if so, the effect of sending a
message "First branch" to the caster is triggered.
However, if the spell guard is not satisfied, the magic engine
examines the second branch. Now, if the caster has 20 spellpoints,
we INSTEAD trigger the effect of sending the message "Second branch"
to the caster.
- Spell guards
Spell guards can be omitted; in that case, just use the effect
itself. Otherwise they can be any of the following:
* MANA x: Require x spellpoints to be present. If this spellguard
is taken, x mana will be consumed implicitly. This requirement is
cumulative.
* CASTTIME x: Require that the caster spend x milliseconds until
the next spell can be cast. This requirement is cumulative. If
the total casttime for a spell is less than the global variable
min_casttime, then the latter supercedes the specified spell cast
delay.
* REQUIRE <expr>: Test that the specified expression evaluates to
nonzero and does not fail. Requirements are cumulative.
* CATALYSTS <items>: Ensure that the caster possesses all specified
items. This effect is cumulative.
* COMPONENTS <items>: Ensure that the caster possesses all specified
items. If the branch suceeeds, all items specified here are
consumed. This effect is cumulative.
Items can be specified as follows:
* [ 700, 701 ] -- require one item of item ID 700 and one of 701.
* [ 700, 3 * 701 ] -- require 1 item of item ID 700 and 3 of 701.
* [ "Pearl" ] -- require one item named `Pearl' in the item DB.
Spell guards can be combined as follows:
* `or': disjunction. The first matching path is taken.
* (a, ..., n): conjunction. a, n, and everything in between must be
satisfied.
* a => b: Implication. If `a' is satisfied, try to satisfy `b'.
This operation is useful to combine different branches (see
below.)
Different branches of spell effects are separated by the vertical
bar `|'. For example,
SPELL plugh (message : STRING) : "zzx" =
MANA 5 => ( (CATALYSTS ["Pearl"]) =>
EFFECT message (caster, "First branch");
| (MANA 20) =>
EFFECT message (caster, "Second branch");)
will always try to deduct 5 Mana points but then make a choice of
whether to go to the first branch (if the player has `Pearl') or to
the second (if the player does not have `Pear' but has another 20
spell points, for a total of 25 spell points, all of which will be
consumed in that case.)
- Effects
Effects describe what happens when a spell is triggered. Each
spell has at least one EFFECT specification, which looks as follows:
EFFECT <effectlist> [ ATTRIGGER <effectlist> ] [ ATEND <effectlist> ]
The three parts are as follows:
* EFFECT: All effects here are executed as soon as the spell is
triggered.
* ATEND: All steps described here are executed when the spell
finishes. Note that the spell may remain active after all steps
from the EFFECT section have been taken; this happens when the spell
triggers a status change (using the `status_change' operation,
as described in the operations library). In that case the spell
will terminate only after all status changes have finished.
The ATEND section is not called when the spell finishes due to the
caster dying.
* ATTRIGGER: This section is used only for the `override_attack'
operation and described there.
Before effects are executed, the engine defines the following
variables:
* The parameter (if any)
* caster : entity (the caster of this spell)
* spellpower : int (the caster's spellpower, normally 6 -- 198)
* location : location (the location the spell is currently at)
* self_spell : spell (the current spell)
* self_invocation : invocation (the current spell instance)
The engine can then execute the following effects from the effect list:
* SKIP; # a no-op
* ABORT; # Abort the spell, don't run ATEND, don't consume a
# trigger charge (cf. `override_attack')
* END; # Skip to the ATEND block
* WAIT <expr>; # Wait <expr> milliseconds before continuing
* <id> = <expr>; # Set <id> to the result of evaluating <expr>
* (<s1> ... <sn>) # Execute statements <s1> through <sn> in sequence
* IF <c> # Test condition <c>. If nonzero,
THEN <s1> # execute <s1>. Otherwise,
ELSE <s2> # execute <s2>.
# The `ELSE' branch can be omitted.
* FOREACH <k> <id> IN <expr> DO <s>
# Evaluate <expr> to an area, find all entities in
# the area that match <k>, randomise this list,
# bind <id> to each in turn and execute <s>.
Example:
FOREACH ENTITY t IN rbox(location(caster), 20)
DO aggravate(t, 0, caster);
# This aggravates all entities within 20 paces of
# the caster to attack the caster.
Valid values for <k> are
+ ENTITY : PC or mob
+ PC
+ MOB
+ TARGET : mob, PC (but only if we are on a PvP map)
* FOR <id> = <start> TO <stop> DO <stmt>
# This will iterate from <start> to <stop> (inclusively), bind
# <id> to the current iteration value, and execute <stmt>.
* BREAK;
# This will break out of the current FOR loop, FOREACH loop, or
# procedure.
* <id> ( <expr1>, ..., <exprn> );
# This executes an operation. See `Operations', below, for a
# list.
* CALL <id> ( <expr1>, ..., <exprn> );
# This will execute a procedure, after binding the actual
# parameters from <expr1> to <exprn> to the formal procedure
# parameters.
* { ... }
# This executes arbitrary eAthena script code. The following
# variables script variables are bound implicitly:
# - @caster_name$ is the name of the spellcaster
# - @caster and @target are also bound, to useless values (sorry.)
#
# By default, script popup boxes are sent to the caster. This can
# be overridden by setting the special `script_target' variable.
Procedures:
-----------
Procedures are defined as
PROCEDURE <id> ( <id>, ... , <id> ) = <effectlist>
For example,
PROCEDURE testproc(x) = message(caster, "foo(" + x + )");
y = 10;
x = 20;
defines a procedure `testproc' with one formal parameter `x'.
Procedure execution is nonrecursive and uses dynamic scoping. The
latter means that it can modify variables in the caller's scope. In
the above example, the assignment to `y' will be visible to the
caller. The assignment to `x' however will be not be visible, since
that assignment goes to the parameter and is therefore limited in
scope to `testproc'. More precisely,
EFFECT x = 0; y = 0; testproc(1);
message(caster, "x=" + x + ", y=" + y);
would print
foo(1)
x=0, y=10
(note how the update to x is isolated from the caller.)
Functions:
----------
This section documents the function API.
The following functions are available:
+ max : int * int -> int
Pick the greater of two values.
+ min : int * int -> int
Lesser of two values.
+ is_in : location * area -> bool
Test whether a location is within an area.
+ if_then_else : bool * 'a * 'a -> 'a
Test a condition (first parameter). If the contition is nonzero,
return the second parameter, otherwise the third parameter.
+ skill : entity * int -> int
Get the skill level that the `entity' has for the skill id.
+ dex : entity -> int
+ agi : entity -> int
+ int : entity -> int
+ vit : entity -> int
+ str : entity -> int
+ luk : entity -> int
+ hp : entity -> int
+ sp : entity -> int
+ max_hp : entity -> int
+ max_sp : entity -> int
+ level : entity -> int
Status attributes.
+ dir : entity -> dir
Direction that the entity is currently facing.
+ not : int -> int
Logical negation. (NOT bitwise negation.)
+ name_of : entity -> string
| spell -> string
Retrieves the name either of an entity or of a spell.
+ location : entity -> location
Determines the location that the specified entity presently
occupies.
+ random : int -> int
random(6) yields a random value from 0 to 5.
+ random_dir : int -> dir
random_dir(0) yields N, S, E, or W.
random_dir(1) yields N, S, E, W, SE, SW, NE, or NW.
+ hash_entity : entity -> int
Retrieve a number idenfying the entity.
+ is_married : entity -> int
Tests whether the entity is married.
+ partner : entity -> entity
Retrieves the entity's partner, if online, or fails otherwise.
+ awayfrom : location * dir * int -> location
awayfrom(loc, dir, distance) returns a location obtained by moving
at most `distance' towards `dir', starting at `loc'. If the move
hits an obstacle, we stop before the obstacle.
+ failed : 'a -> bool
True iff the input was the special failure value.
+ pc : string -> entity
Looks up a player character by name. Fails if there is no match.
+ npc : string -> entity
Looks up an NPC by name. Fails if there is no match.
+ distance : location * location -> int
This is the `fake square distance': The maximum of delta x and
delta y between the two locations.
+ rdistance : location * location -> int
This is the `real' distance (square root of the square of dx, dy)
+ anchor : string -> area
Looks up a teleport anchor by name and returns the associated
area. Fails if the result is not an area.
+ random_location : area -> location
Pick a random location from within an area.
+ script_int : entity * string -> int
Read a player script variable as an integer.
+ rbox : location * int -> area
rbox(l, n) computes rectangular box centered at `l', with a
`radius' of n. The box contains (n*2 + 1)^2 squares.
+ count_item : entity * int -> int
| entity * string -> int
Counts the number of instances of the specified item that the
entity has. Items may be given by ID or by name.
+ line_of_sight : location * location -> int
Determines whether there is a line-of-sight connection between the
two locations.
+ running_status_update : entity * int -> bool
Determines whether the specified status update is still active.
+ element : entity -> int
Determines what element the entity is associated with
+ element_level : entity -> int
Determines what element level the entity has
+ has_shroud : entity -> int
Determines whether the player is presently shrouded (i.e., whether
the player's name is being obscured.)
+ is_equipped : entity * int -> int
: entity * string -> int
Determines whether the player has equipped the specified item
+ spell_index : spell -> int
Determines a unique index assigned to each spell
Operations:
-----------
This section documents the operations API.
+ sfx : entity * int * int -> ()
| location * int *int -> ()
Trigger a special effect (specified by sfx ID) for an entity or a
location. The int specifies a delay until the effect is issued.
+ itemheal : entity * int * int -> ()
itemheal(entity, hp, sp) triggers item healing. This will
hopefully be slowed down if an appropriate server patch is
installed.
+ instaheal : entity * int * int -> ()
itemheal(entity, hp, sp) heals instantly.
+ shroud : entity * int -> ()
shroud(entity, flags) hides the entity's name (only for PCs).
Flags: 0x01: Hide PC'ss name when talking
0x02: Shroud vanishes when player picks something up
0x04: Shroud vanishes when player talks
The shroud will not affect players in visible range until the
entity has left and re-entered their field of vision. This can be
enforced by warping.
+ unshroud : entity -> ()
Counter a shroud.
+ message : entity * string -> ()
Send a message to the entity.
+ messenger_npc : location * int
* string * string * int -> ()
messenger_npc(location, image, npc_name, message, duration)
creates a messenger NPC looking like the `image' at `location',
with name `npc_name' and delivering the `message' when clicked
upon. The NPC disappears after the `duration' in ms has expired.
+ move : entity * dir -> ()
Move the entity into the specified direction, unless that
direction is blocked.
+ warp : entity * location -> ()
Warp entity to specified location.
+ spawn : area * entity * int * int * int * int -> ()
spawn(area, owner, mob_id, attitude, count, lifetime) spawns for a
limited `lifetime' (in ms) a total of `count' monsters of kind
`mob_id' in `area'. `attitude' specifies how they behave:
0 : attack everyone
1 : be friendly
2 : attack enemies of `owner' and give XP to `owner' if successful
+ banish : entity -> ()
If the entity was spawned by the `spawn' operation, eliminate it.
+ status_change : entity * int * int
* int * int * int * int -> ()
status_change(entity, status, v1, v2, v3, v4, duration) initiates
a status change. The precise status change (and the meaning of
`v1', `v2', `v3', `v4') varies depending on `status'. This
operation may delay spell termination (and the ATEND effect).
ATEND can therefore be used to notify the caster that the status
change has finished.
+ override_attack : entity * int * int
* int * int *int -> ()
override_attack(entity, charges, delay, range, icon, animation)
overrides the entity's current attack (only for PCs). The entity
will have `charges' attacks that instead result in calling the
ATTRIGGER effect for this spell. When this operation is called,
the spell environment (variables etc.) is cloned into a separate
invocation. This special invocation will be triggered every time
the entity tries to attack, until they have run out of charages (at
which time the previous behaviour is restored.)
`delay' specifies the attack delay.
`range' specifies the attack range as shown in the client GUI.
`icon' is presently unused.
`animation' is the attack animation ID that should be used.
Note that if the ATTRIGGER effect ABORTs, no charge will be
consumed.
ATTRIGGER can refernece the player's target via the `target'
variable.
Example:
SPELL tshuffle : "zvp" =
(MANA 1, CATALYSTS ["Pearl"]) =>
EFFECT
override_attack(caster, 3, 500, 10, 700, 31);
ATTRIGGER
IF (not (line_of_sight(location, location(target))))
THEN (message (caster, "No line of sight!"); ABORT;)
FOR i = 0 TO 10 DO (move(target, random_dir(0)););
This overrides the caster's attack for three attacks (attack delay
500, range 10) to instead randomly move around any entity that the
player tries to attack by up to 11 paces.
+ create_item : entity * int * int -> ()
| entity * string * int -> ()
create_item(entity, item, count) gives the `entity' `count'
instances of `item'. As usual, `item' can be either a string name
or an item ID.
+ aggravate : entity * int * entity -> ()
aggravate (victim, mode, target) causes the `victim' to
mode = 0: attack `target'
mode = 1: become universally permanently aggressive
mode = 2: both of the above
+ injure : entity * entity * int * int -> ()
injure(attacker, defender, hp, sp) causes damage to the defender
from the attacker (possibly killing, giving XP etc.), unless the
defender is immortal (NPC) or a PC on a non-PvP map.
+ emote : entity * int -> ()
Issues the specified emotion to the specified entity.
+ set_script_variable : entity * string * int -> ()
Sets a script variable to the specified value
+ set_hair_colour : entity * int -> ()
Sets the hair colour of the specified entity to the specified
value (must be a PC).
+ set_hair_style : entity * int -> ()
Adjusts the hair style of a PC.
+ drop_item : location * (int | string) * int * int -> ()
drop_item(place, "name", count, duration) drops `count' items
(where count may be zero) of name "name" at `place'. The items
vanish again after `duration'.
+ drop_item_for : location * (int | string)
* int * int * entity * int -> ()
drop_item_for(place, obj, count, duration, owner, delay) works
like drop_item(place, obj, count, duration), except that the item
can only be picked up by `owner' for the next `delay'
milliseconds, modulo pickup rules (spousal pickup, out-of-range).
Script API updates:
-------------------
Two new script API functions are available:
* getspellinvocation : string -> string
Looks up a spell by spell ID and returns the spell's invocation.
* getanchorinvocation : string -> string
Looks up a teleport anchor by anchor ID and returns the invocation.
Syntax Reference:
-----------------
SPELLCONF ::= (GLOBAL | ANCHOR | SPELL | PROCEDURE | ';')* (* The ';' are only for decorative purposes *)
VALUE ::= <int>
| <hexint>
| <id>
| <string>
| <dir> (* one of {N, S, E, W, NE, SE, NW, SW} *)
EXPR ::= (VALUE)
| (AREA)
| (EXPR) '+' (EXPR)
| (EXPR) '*' (EXPR)
| (EXPR) '-' (EXPR)
| (EXPR) '/' (EXPR)
| (EXPR) '%' (EXPR)
| (EXPR) '<' (EXPR)
| (EXPR) '>' (EXPR)
| (EXPR) '<>' (EXPR)
| (EXPR) '=' (EXPR)
| (EXPR) '!=' (EXPR)
| (EXPR) '==' (EXPR)
| (EXPR) '<=' (EXPR)
| (EXPR) '>=' (EXPR)
| (EXPR) '&&' (EXPR)
| (EXPR) '||' (EXPR)
| (EXPR) '|' (EXPR)
| (EXPR) '^' (EXPR) (* XOR *)
| (EXPR) '&' (EXPR) (* binary AND *)
| (EXPR) '<<' (EXPR)
| (EXPR) '>>' (EXPR)
| <id> '(' ((EXPR) /* ',') ')'
| <id>
| '(' (EXPR) ')'
INVOCATION ::= <string> (* used for convenience *)
LOCATION ::= '@' '(' (EXPR) ',' (EXPR) ',' (EXPR) ')' (* <map name, x, y> *)
AREA ::= (LOCATION)
| (LOCATION) '@' '+' '(' (EXPR) ',' (EXPR) ')' (* width and height around location, passable only *)
| (LOCATION) 'towards' (EXPR) ':' '(' (EXPR) ',' (EXPR) ')' (* towards dir: Bar-shaped, width and depth; only NSEW supported *)
ITEMS ::= '[' (ITEMC) /+ ',' ']'
ITEMC ::= (ITEM)
| <int> '*' (ITEM)
ITEM ::= <int>
| <id>
* global
GLOBAL ::= 'CONST'? <id> '=' (EXPR) ';'
Available globals:
- min_casttime : int (* min # of ticks for each spell (BEFORE scaling according to battle.conf) *)
- obscure : int (* obscure percentage *)
* teleport-anchor
ANCHOR ::= 'TELEPORT-ANCHOR' <id> ':' (INVOCATION) '=' (EXPR)
For example,
TELEPORT-ANCHOR t = "tulimshar" @("map_3-1.gat", 44, 70)
creates a teleport anchor with name `t' and invocation `tulimshar' at the speicfied location.
* spell
SPELL ::= spellmod 'SPELL' <id> (ARG)? ':' (INVOCATION) '=' (SPELLDEF)
SPELLMOD ::= ('SILENT' | 'LOCAL')*
(silent: invocation silently dropped. local: `location' variable doesn't change after spell init.)
ARG ::= '(' <id> ':' (ARGTYPE) ')"
ARGTYPE ::= 'PC' (* yields a pc, or self *)
| 'STRING'
SPELLDEF ::= ((SPELLBODY) /* '|')
| 'LET' (DECL)* 'IN' ((SPELLBODY) /* '|')
SPELLBODY ::= (SPELLGUARD) '=>' (SPELLBODY)
| 'EFFECT' (EFFECT) ('ATTRIGGER' (EFFECT))? ('ATEND' (EFFECT))?
(* `ATTRIGGER' is executed as a separate effect if the spell is `triggered'. If the trigger has a target, it is denoted
* in the variable `target'.
* `ATEND' is invoked for normal termination, i.e., after the spell is over or has been dispelled. `ATEND' is NOT used
* for the triggered effect; instead, spawn a separate spell in ATTRIGGER if that is desired. *)
DECL ::= <id> '=' (EXPR) ';'
SPELLGUARD ::= (PREREQ)
| (SPELLGUARD) 'or' (SPELLGUARD)
| '(' (SPELLGUARD) /+ ',' ')'
PREREQ ::= 'REQUIRE' (EXPR)
| 'CATALYSTS' (ITEMS)
| 'COMPONENTS' (ITEMS)
| 'MANA' (EXPR)
| 'CASTTIME' (EXPR) (* # of ticks until the next spell can be cast *0
EFFECT ::= EFFECT ';' EFFECT
| '(' (EFFECT) ')'
| 'SKIP' (* no-op *)
| 'ABORT' (* abort spell. If used in a trigger, no charges will be consumed. *)
| 'END' (* skip to atend *)
| 'BREAK' (* break out of loop *)
| <id> '=' (EXPR) (* interpreted in the current context, eval'ds trictly *)
| 'FOREACH' (SELECTION) <id> 'IN' (AREA) 'DO' (EFFECT) (* randomises the subjects first *)
| 'FOR' <id> '=' (EXPR) 'TO' (EXPR) 'DO' (EFFECT) (* bounds are evaluated when the loop begins, no updates are respected *)
| 'IF' (EXPR) 'THEN' (EFFECT) ('ELSE' (EFFECT))?
| 'WAIT' (EXPR) (* amount in ticks before continuing. *)
| <id> '(' (EXPR) /* ',' ')' (* operation *)
| 'CALL' <id> '(' (EXPR) /* ',' ')' (* procedure call *)
| '{' ... '}' (* script *)
SELECTION ::= 'PC'
| 'MOB'
| 'ENTITY' (* MOB or PC *)
| 'TARGET' (* like ENTITY, but includes PCs only on PvP maps *)
(* | 'SPELL' *)
* procedures
Procedures may be invoked via `CALL'. They use dynamic scoping.
PROCEDURE ::= 'PROCEDURE' <id> '(' <id> /* ',' ')' '=' (EFFECT)
