K65 Evaluator

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Evaluator in K65 is compile-time executed expression language very similar to C/C++ expressions.

Evaluator introduction

In every place where the compiler expects a single number, you can invoke the evaluator by simply using square brackets.

data NumberFour {

The evaluator can be also invoked freely outside any section body, e.g. to set variables:

[ FOUR = 4 ]

which can be later used freely as compiler constants and within further evaluator expressions:

data FourFiveSix {
  FOUR             // value of variable FOUR defined earlier
  [FIVE = FOUR+1]  // defines variable FIVE and returns its value
  [FIVE+1]         // uses recently set FIVE value

Evaluator operators

Available operators and their precedence levels are similar to operators in C and C++

Precedence Operator Description Associativity


++ Suffix increment Left-to-right
-- Suffix decrement
() Function call
[] Array subscripting
. Single argument function call
3 ++ Prefix increment Right-to-left
-- Prefix decrement
+ Unary plus
- Unary minus
! Logical NOT
~ Bitwise NOT (One's Complement)
5 * Multiplication Left-to-right
/ Division
% Modulo (remainder)
6 + Addition Left-to-right
- Subtraction
7 << Bitwise left shift Left-to-right
>> Bitwise right shift
8 < Less than Left-to-right
<= Less than or equal to
> Greater than
>= Greater than or equal to
?> Select greater value (maximum)
?< Select smaller value (minimum)
9 == Equal to Left-to-right
!= Not equal to
10 & Bitwise AND Left-to-right
11 ^ Bitwise XOR (exclusive or) Left-to-right
12 | Bitwise OR (inclusive or) Left-to-right
13 && Logical AND Left-to-right
14 || Logical OR Left-to-right
15 ?: Ternary conditional Right-to-left
16 = Direct assignment Right-to-left
+= Assignment by sum
-= Assignment by difference
*= Assignment by product
/= Assignment by quotient
%= Assignment by remainder
<<= Assignment by bitwise left shift
>>= Assignment by bitwise right shift
&= Assignment by bitwise AND
^= Assignment by bitwise XOR
|= Assignment by bitwise OR


, Expression list (executes in sequence, returns value of the last) Left-to-right

Evaluator functions

Following functions are available within evaluator expressions.

Function name Description
acos( x ) Arcus cosinus
addbyte( sec, b ) Add byte b to section sec
asin( x ) Arcus sinus
ceil( x ) Round up to nearest integer
clamp( x, min, max ) Clamp x to range min to max
color( r, g, b ) Return palette index for nearest color to color (r,g,b)
color( x ) Return palette index for nearest color specified in format 0xRRGGBB
cos( x ) Cosinus
error( err ) Print error message err ane terminate compilation
floor( x ) Round down to nearest integer
frac( x ) Get fractional part ( x-floor(x) )
index( tab, x ) 1-dimensional indexing operator ( same as tab[x] )
index( tab, x, y ) 2-dimensional indexing operator ( same as tab[x,y] )
max( a, b ) Maximum
min( a, b ) Minimum
pow( x, y ) Power function
print( msg ) Print message msg
rnd( ) Random value 0 <= x < 1
round( x ) Round to nearest integer
sin( x ) Sinus
size( sec ) Current size of section sec
sqrt( x ) Square root