13. Arithmetics

WLA is able to solve really complex calculations like

-((HELLO / 2) | 3)
skeletor_end-skeletor
10/2.5

so you can write something like

LD HL, data_end-data
LD A, (pointer + 1)
CP (TEST + %100) & %10101010

WLALINK also has this ability so it can compute the pending calculations WLA wasn’t able to solve.

NOTE! The assembler has only a limited capability to turn labels into addresses. Often label references are left for the linker to solve. Currently the assembler can do so when the label is outside .SECTION s or inside FORCE or OVERWRITE .SECTION s and the label is defined before it is referenced. Many directives like .ASSERT require data that the assembler can immediately solve so you might run into problems when feeding labels to directives.

The following operators are valid:

|	bitwise or
&	bitwise and
^	power
<<	bitwise shift left
>>	bitwise shift right
+	plus
-	minus
#	modulo
~	bitwise xor
*	multiply
/	divide
<	get the low byte
>	get the high byte
:	get the bank byte of an address

Note that you can do NOT using XOR

- ``VALUE_A ~ $FF``   is  8-bit NOT
- ``VALUE_B ~ $FFFF`` is 16-bit NOT

Unary XOR (e.g., ~$FF) is the same as NOT.

.IF conditions have the following additional operators:

!	not
<	smaller than (note that outside .IF this is something else)
>	larger than (note that outside .IF this is something else)
<=	smaller or equal
>=	larger or equal
==	equal
!=	unequal
||	logical or
&&	logical and

Here’s a table of the precedence of the operators in calculations and conditions (higher priority operators come first):

( )	expression
~ !	unary
< > :	low byte / high byte / bank (outside .IF)
/ * # ^	multiplicative
+ -	additive
<< >>	bitwise shift
< > <= >=	relational (only inside .IF)
== !=	equality (only inside .IF)
&	bitwise and
~	bitwise xor
|	bitwise or
&&	logical and
||	logical or

WLA computes internally with real numbers so (5/2)*2 produces 5, not 4.