Atalan source code is ASCII text file. It does not support reading of UTF-8 files, it can however safely skip UTF-8 header, so if you mistakenly safe your source code using UTF-8 (hello PSPad), there should be no problem.
Atalan is case insensitive.
Numeric and string literals may be defined.
65535 dec
$494949 hex
%0101010 bin
"C" character string
It is possible to separate parts on a numeric constant by apostrophe.
65'535
$ff'ff
%0101'0101'0101'1111
Anything after ; is comment.
Indent may be used to define blocks of code for control structures.
Identifiers must start with letter and may contain numbers, underline and apostrophes. Identifier may be enclosed in apostrophes. In such case, it may contain any characters including apostrophe.
Example:
name
x1 x2
x'pos
'RH-'
'else' ; this is identifier, even if else is keyword
Variables do not have to be defined, they are declared using assignment action.
name ["@" adr] ["," name]* [":" [min ".." max]|[var] [ "(" dim ["," dim2] ")" ] ["=" value ["," value]
name Name of variable, multiple variables may be declared/assigned (separated by comma) adr Place variable at specified address or register.
Type is declared using one of following methods:
Type is defined using 'type' keyword.
type short:-128..127 ; signed byte type
type byte:0..255
type word:0..65535
type int:-32768..32767
type long:0..$ffffff
type char:byte
Constant is variable, that is initialized during declaration and never assigned again. Array may be used as const to define static data.
const TAB = 3 * 3 ; it is possible to use expressions to evaluate constants
const SPC = 32
const DIGITS:char(16) = "0","1","2","3","4","5","6","7","8","9","A","B","C","D","E","F"
Const keyword introduces a block, so it is possible to declare multiple constants at once.
const
TOP = 1
BOTTOM = 2
It is possible to place variable to specified address. This is usually used
to define system and hardware registers.
PCOLR @704:byte(4) ; player & missile graphics color (4 missiles)
COLOR @708:byte(5) ; playfield color
SDLSTL @560:ptr ; pointer to beginning of display list
STICK @632:byte(4)
Value of some hardware registers changes automatically.
It is necessary to mark such variables as 'in' or 'out'.
x = y
x,y:int
x,y = 3,4
x,y = y,x [TODO]
x,y = cursor
Anonymous variable may be assigned (like POKE in BASIC). It is possible to specify type too.
@712 = 0 ; set background color to black
@$230:ptr = my_dlist
@buf:byte(100) = 0 ; set 100 bytes at address stored in variable buf to 0 (memset)
Label is specified as variable located at address where address is not specified. Note, that there must be at least one space after label definition.
name@
Integer type is declared using numeric range. Compiler automatically decides, how many bytes to use.
byte:0..255
word:0..$ffff
int:-32768..32767
flag:0..1
It is possible to associate constant with integer type. Associated constant works like enum, but the type remains integer (i.e. you can still assign numbers to them).
color:0..255
const gray:color = 0
const pink:color = 4
When using associated constant, it must be preceded by type name and dot. It is not necessary, when the type is clear (assigning or comparing with variable of the )
c1:0..255
c2:color
c1 = color.gray
c2 = pink ; c2 is of type color, color. is not necessary
Enumerators are integer types, that define list of named values, that may be assign to them.
Enums are declared using enum keyword optionally followed by numeric range. If numeric range is specified, all constants associated with this enum must be in the range. If not specified, range is computed automatically based on specified values.
button_state:enum (pressed = 0, not'pressed = 1)
color: enum
gray
pink
purple
Structure is defined as list of variable declarations. Either "," or new line may be used as separator.
xcoord:0..319
ycoord:0..239
point:(x:xcoord, y:ycoord)
point:
x:xcoord ; x screen coordinate
y:ycoord ; y screen coordinate
Using @ inside structure places the variable at specified offset from the beginning of a structure. Structures with 'holes' can be defined this way, even if it is not usually very useful.
audch:
f:byte ; frequency
c:byte ; control
aud@$D200:audch(4)
Array is defined using keyword array.
name:array [(min..max|count)[,(min..max|count)]] of byte
If the array size is defined using single value, the value defines maximal index. Minimal index is then 0. So x:array(31) defines array of 32 elements (index 0..31).
Array can be defined as one or two dimensional.
It is possible to initialize arrays using literals. Array constants are defined as comma separated list of values. It is not necessary to define dimension for initialized array.
If there is reference to array variable as part of array initializers, pointer to that array is stored in the array. This is possible for byte arrays too, in such case the element will occupy multiple bytes (usually 2 bytes for 8-bit processors).
When some item is to be repeated several times in initialization, it is posible to use <n> TIMES <item> construct. <n> must be integer number. If it is lower or equal 0, no item will be generated.
disp:array(0..39,0..23) of byte
const a:array of byte = 3 times 112, disp, 0
;Array has dimension 0..6
Array element is accessed using parentheses.
arr:array(10) of byte
arr(1) = arr(2)
scr:array(39,23) of byte
arr(0,0) = 65
When assigning single variable to array, all items in array are set.
screen:array(39,239) of byte
screen = 0 ; clear the screen (fill with 0)
* / Multiplication, division
+ - Addition, substraction
lo hi Low/high byte of a word (lo $abcd = $ab, hi $abcd = $ab)
and or Bit operators
xor not Bit operators [TODO]
( ) Parentheses
Expression used in conditions have slightly different rules than normal expressions. They (at least in theory) evaluate to true/false. If simple value is used, it's 0 value means false, any other value true.
not Logical negation
and or Logical operators with short circuit evaluation
= <> < > <= >= Relational operators [TODO: == and <> working]
is isn't Same as '=' '<>' (lower priority). [TODO]
String constant used as command will be printed to screen.
"Hello, World!"
""
"I'm here!"
Square braces may be used to insert variables into the printed string.
x = 4
y = 6
z = x + y
"Sum of [x] and [y] is [z]."
Variable type is automatically recognized, there is no need to specify it.
Label is be defined as
label@
It is possible to jump on specified label unconditionally using goto.
goto label
It is also possible to jump to address specified in variable.
x:word
x = 1000
goto x ; jump to address 1000
Control structures organize code in blocks. Block is list of commands.
Block may be defined using several methods:
Full conditional statement is supported. Note, that the blocks may be defined using indent. It is possible to optionally use THEN keyword after condition. Arbitrary number of else if sections is supported.
if <cond> [then]
<code>
else if <cond2>
<code>
else
<code>
Short one-line version is supported.
if <cond> then <code>
Again, it is not necessary to use then:
if <cond> goto <label>
Repeat commands in the block as long as the specified condition is true.
while <cond>
<block>
Repeat commands in the block as long as the specified condition is not true.
until <cond>
<block>
Loop iterating over variable.
for <var>
<body>
The variable must be integer. All possible values will be iterated, depending on variable type. The variable must be defined in advance, after the end of loop, it will contain last processed index.
It is possible to specify condition for loop using where keyword.
for <var> where <filter>
<body>
Loop body is executed only if the condition after where is true.
It is possible to combine the loops. Following code will write numbers between 1 and 10000, until end is reached of Q key is pressed.
for k:1..10000 until CHAR1 = Q
"[k]"
Procedures can be defined using proc type. After the proc keyword follows block defining procedure arguments. Arguments marked using "<" are output arguments ( results).
name ":" "proc" args = code
addw:proc i:word j:word >k:word =
k = i + j
add3: word proc
i:word
j:word
k:word
>result:word
=
result = i + j + k
Procedure may define more than one output arguments (results).
sumdiv:proc a,b:byte >sum:byte >div:byte =
sum = a + b
div = a - b
a:byte
b:byte
a,b = sumdiv 10 3
"Sum is [a], div is [b]"
It is possible to define local procedure inside other procedure.
set'line'color:proc =
wait'line:proc =
WSYNC = 0
COL'BK = VCOUNT * 2 + RTCLOCK
wait'line
Procedure may be declared using type of another procedure.
subw:addw =
k = i - j
It is possible to define routines in ROM using @ syntax.
reset@$E034:proc