Cual - Cuyo Animation Language

Cual is the main language used to describe the animations in cuyo. It's the stuff between the << >> brackets in the level description files (xxx.ld).

This man page is not a complete description of how to write levels for cuyo; it only describes Cual. And it's still under construction. See the file "example.ld" to get an idea of how the rest of the level description works. There's also a bit of example Cual code in "example.ld". And of course, all the existing levels are examples.

Note that Cual is probably still very buggy. It has almost not been tested. (The existing levels work, but that's all.) So if strange things happen and you're sure it's not your fault, tell me (cuyo@karimmi.de).

Each blob has its own (main) Cual procedure which does the drawing and the animation stuff. The procedure only depends on the kind of the blob, that is, it is the same for blobs of the same kind. However each blob has its own instance of the variables.

In every game step, the procedure of each of the blobs is called once. (There are 10 game steps per second.) It has to draw the blob each time, even if nothing has changed. (However, there's an internal routine in cuyo which checks if the same is drawn as in the last step and which then supresses the drawing.)

There may be other procedures associated to a kind of blob, which are executed at special events, for example when a falling blob lands. In contrast to the main procedure, these event handlers are not allowed to draw anything. See section "event handlers" for a list of the existing events.

The name of the main procedure of a blob (the one which draws the blob) is the name of the kind of the blob. Normally, that name is the word listed after pics= entry in the .ld file; but if that "word" contains a dot, only the part before the dot makes up the name. (E. g. with pics=redblob.xpm,greenblob.xpm, the names are "redblob" and "greenblob".)

The name of an event handler procedure is the name of the kind, followed by a dot, followed by the event name. (E.g. "redblob.land" for the landing event of the redblob from above.)

[Explain the default procedures.]

Inside << >>, variable and procedure definitions are expected.

procname = code ; Defines a "procedure". The next section describes how code looks like.

Example:

redblob = {

schema16; 0*;

1; A,B,C; *;

};

var varname1 = def1, varname2 = def2, ... ; Defines variables with default values. The default value can be omitted (together with the "=" before it). Then, the default value is zero. See section about variables and constants about the meaning of the default value.

A code fragment can be one of the following:

{ code; code; ...} Executes one command after the other.

code, code, ... This is useful for simple animations. Executes exactly one of the commands: In the n-th call, the n-th command is executed. After the last command, the first one is executed again. However, if one of the commands is "busy" (see section about busieness), this one will be executed until it stops being busy, and only after that, the next command will be executed.

procname Executes the procedure procname, which has to be already defined. The result is the same as if the code from procname would have been inserted in that place.

&procname Executes the procedure procname; however, every instance of such a procname is the same. This concerns busieness and the state of an animation sequence. (See sections BUSIENESS and AMPERSAND-CALL.)

busy

Does nothing except being busy. (See section BUSIENESS.)

varname = expr Sets the variable. See section "VARIABLES AND CONSTANTS" for details.

The same with +=, -=, *=, /=, %=

Does what you would expect.

[ varname = expr ] code Sets the variable varname to expr, executes code and then resets the variable to the old value.

number A shortcut for "file = number".

letter A shortcut for "pos = number", where different letters mean different numbers: A: 0, B: 1, ..., Z: 25, a: 26, ..., z: 51

*

Draw the icon specified by the variables kind, file and pos. May also draw only a part of the icon, if specified by the variable qu (see section about variables and constants).

*@(x, y) Like *, but draws the icon at relative coordinates x, y. Relative drawing is always performed after all other drawing. (See section about variables and constants for more details about @.)

if expr if-arrow if-code ; if expr if-arrow if-code else [else-arrow] else-code ; The arrows can be either "->" or "=>". If you use "->" arrows, it does exactly what you would expect.

If the if-arrow is "=>", then once the expression gets true, the if-code will be executed every subsequent time (without testing the condition), as long as it is "busy". More details see section BUSIENESS.

If the else-arrow is "=>", then once the expression gets false, the else-code will be executed every subsequent time as long as it is busy.

If the else-arrow is omitted, "=>" is used. (But this might change in the future.)

switch {

expr1 arrow1 code1 ; expr2 arrow2 code2 ; ... } The arrows can be either "->" or "=>". Does the same as:

if expr1 arrow1 code1

else if expr2 arrow2 code2

...

The last expr may be omitted to get an else part without further condition.

bonus(expr) The player gets expr bonus points.

message(String) The string is displayed (blinking) on the screen. To be used together with bonus(...).

Example:

bonus(5);

message("You get 50 bonus points");

explode

Makes the blob explode. For the next 8 steps or so, the blob is still what it was before, but the explosion is drawn over the graphics. After that, it's changed to a nothing-blob. There's a shortcut for drawing: You may omit the ";" between a number, a letter and the "*".

The only data type in cual is int. Bools are represented by 0 and 1, like in C. (And any number other than 0 is interpreted as true, if a boolean is expected.)

Of course, variables, constants and numbers are expressions, and you can use parentheses. There are the following operators:

The following operators do exacly the same as in C (listed here by precedence): tab(#); l l. ||#Boolean or &&#Boolean and ==, !=, <, >, <=, >=#Comparision !#Boolean not +, -#Add, substract *, /, %#Multiply, divide, modulo

[Insert precedence of special operators.]

The following special operators exist:

expr == number1 .. number2 Is true, if expr lies between the two numbers. You may also omit one of the numbers. (Then, it does the same as <= resp. >=.) Note that this operator might change in the future. (I plan to make something like "expr in set" in pascal.)

number1 : number2 Is true (that is, 1) with probability number1/number2

neighbour_pattern neighbour_pattern is a sequence of six or eight characters 0, 1 and ?. It is true if the sequence fits to the neighbour sequence of the blob. The neighbour sequence is a string of "0"s and "1"s with a "1" for each neighbour of the same kind, starting above and going clockwise. This way, you get a string of "0"s an "1"s (six or eight, depending on wether this level is in hex mode).

Example: 1???0??? is true iff the blob above this blob is of the same kind and the blob below it is of different kind.

If some blob changes its kind during a step, the expression will still test the neighbours as they were at the beginning of the step. (See the section about variables and constants for details.) The following functions exist:

rnd(expr) Returns a random value between 0 and expr-1

The following kinds of variables and constants exist:

-

User defined variables (see section "Definitions"). At the start of the level (or at the creation of the blob) the value is the default value you provided.

-

System variables. These variables are always defined and have special meanings, e.g. file and pos. Some of them are read-only.

-

Constants. Some of them depend on properties of the level, some are really constant.

Of each variable, there's one instance in each blob. Normally, you access the instance in your own blob, but with the following syntax, you can access variables of other blops:

varname@(dx, dy)

dx and dy are relative coordinates. This can be done for both, reading and writing variables. It also works for system variables (but not for constants). Be aware that dx and dy can't be expressions; they have to be fixed numbers.

In hex mode levels, for odd dx, dy has to be a "half integer", that is a number ending in ".5". This is the only place in Cual where non-integers appear.

There's also one global instance of each variable. That one can be acessed by

variable@

(without coordinates). See section "The Global Blob" for details.

Accessing foreign variables is not as easy as it might look at first glance; it might easily introduce a dependence of the internal order of execution of the blob codes. For this reason,

-

reading variables with @ always returns the value of the variable it had at the beginning of the current step, that is, before any of the blob codes has been executed.

-

when writing variables with @, the write operation will only be executed at the end of the current step. (The write operations are stored in a kind of queue.)

This is also true if a blob accesses its own variables with @(0,0).

The operators +=, -=, etc. are also performed in the future if the left hand side is an @-variable. (To be more precice, the right hand side is calculated instantanousely.)

For illustration, look at the following six statements:

1) X += 1

2) X@(0, 0) += 1

3) X = X + 1

4) X = X@(0, 0) + 1

5) X@(0, 0) = X + 1

6) X@(0, 0) = X@(0, 0) + 1

Only 1) and 3) do the same; they simply increment X by 1.

Statement 4) sets X to one more than it was at the beginning of the step.

Statements 2), 5) and 6) cause the value of X to be changed in the future (after the actual step): X is set to one more than:

2) the value of X just before the change (that is, X is incremented in the future),

5) the actual value of X,

6) the value of X at the beginning of the step.

Some more details

The system variables

The system read-only variables

The Constants:

(No, not Business ;-)

Busieness is a concept to make it easier to implement simple animated sequences which are triggered by certain events. Each code fragment has an internal state which tells if it is busy.

-

Normal statements like assignments are never busy.

-

A chain of commands separated by "," is busy as long as not all of the commands have been executed.

-

code1 ; code2 is busy as long as at least one of code1 and code2 are busy.

Here's an example of how to use busieness for an animation which appears at random intervals:

switch {

1/100 => {B*, C*, D*, E*};

-> A*;

};

This code fragment normally draws the icon at position A (0). But in each step, with a probability of 1/100, an animation sequence consiting of icons B, C, D and E is started. With a normal arrow ("->") after the "1/100", after the step in which B has been drawn, the probability would be 99/100 that A is drawn again. But with the double arrow, the switch statement won't switch back to A until the animation has terminated.

(Btw: It doesn't matter if there's a "->" or a "=>" before the "A*"; A* isn't busy anyway.)

Apart from the normal blobs which you can see on screen, there's one global blob (for the whole game, not one for each player), which, well, isn't really a blob, but behaves a bit like it. It has its own set of variables, and it can have a program which is run once every step. To define such a global program, use "global=code". However, the global variables do exist even if you don't define global code. See section "Variables" on how to access them. Note that the global blob is always executed before any of the normal blobs.

The following events exist:

init

Is called only once, when the blob gets into live, just before the first time its main drawing routine is called.

turn

Is called for falling blobs each time the user presses the turn key.

land

Is called when the steered blob lands.

changeside

Is called when a blob moves from one player to the other, just after the blob has arrived at the new player.

Normal blobs come into life at the beginning of the game, or they fall into life: either as colored blobs, steered by the user, or as grey blobs. When a blob moves (by gravitiy or when rows go from one player to another), it takes its variables with it. When a blob explodes, it does not stop existing. Rather, it transforms into an empty blob. That's important for the variables: The empty blob still has all the variables set to the values they had before; only its kind is different. Empty blobs are everywhere where there's no other blob. (However, the falling blobs steered by the user is in some sense "above" everything else; there are empty blobs beneath them.)

The life of empty blobs is different from the one of normal blobs. Empty blobs are not affected by gravity, and they often start or stop existing. For example, when a single grey blob is falling down, the empty blob below it stops existing when the grey blob arrives and a new empty blob starts existing when the grey blob moves on. There is only one situation in which empty blobs move: When a row moves from one player to the other, and everything moves up resp. down, the empty blobs move, too.

Cual procedures and variables can be defined in different sections of the .ld files:

- Outside of everything; that code is accessible from every level coming after that definition.

- In the section of a level.

- In the section of a kind.

This basically does what you expect. However, there's one thing you might want to know: Even if you define a variable inside a kind, every blob in that level will have that variable. The only effect of defining the variable in the section of a kind is that this kind is the only one which can access it.

To explain a bit what calling a procecure with an & means, here two examples:

Example 1:

<<

myblob = {

...

switch {

myvar -> { 0A*; 1; A,B,C,D; *; 2A*};

-> { 0B*; 1; A,B,C,D; *; 2B*};

};

};

>>

Example 2:

<<

anim = {1; A,B,C,D; *};



myblob = {

...

switch {

myvar -> { 0A*; &anim; 2A*};

-> { 0B*; &anim; 2B*};

};

};

>>

The difference between these examples is what happens when myvar changes. In example 1, the animation "A, B, C, D" will restart at the beginning (because the two animations are different ones); in example 2, the "same" animation is used in both cases, so the animation will simply continue. (Removing the ampersands from example 2 will turn the behaviour to the one of example 1.)

cuyo(6)

Probably a lot. The following are just a few known ones:

There are several problems with busieness and that stuff. There are several situations in which Cual doesn't behave in the way I would like, and in other situations I don't know how Cual should behave.

This man-page is still incomplete. And there's no man-page for the part of the ld-files which is not Cual.