Tool z80asm expressions - marinus-lab/z88dk GitHub Wiki

Expressions

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z80asm accepts expressions in both directives and assembly instructions. The expressions my be required to be constant, i.e. evaluated at assembly time, or non-constant, i.e. evaluated by the linker.

Operators

The expressions follow closely the C-standard with a few additions.

The operators in descending precedence order are:

Operators Description Assoc
+ -
! ~
(...) [...]		 Unary-plus, unary-minus
Logical NOT, binary NOT
Parenthesized expression		 right
** Power right
* / % Multiply, divide, reminder left
+ - Add, subtract left
<< >> Binary shift left, shift right left
= ==
!= <>
< <=
> >=		 Equal
Different
Less than, less or equal
Greater than, greater or equal		 left
& Binary AND left
| ^ Binary OR, binary XOR left
&& Logical AND left
|| Logical OR left
? : Ternary conditional right

Numbers

The assembler accepts numbers in decimal, hexadecimal and binary. Different syntax is allowed to simplify porting of code written for other assemblers. Some of the prefix characters are also used as operators; in this case a space may be needed after the prefix to define it as an operator:

   ld a, %10     ; A = 2 (10 binary)
   ld a, 12 % 10 ; A = 2 (remainder of 12 divided by 10)

All expressions are computed as signed integers with the host platform's integer size (32-bit or 64-bit in the most common platforms).

Decimal numbers are a sequence of decimal digits (0..9). Leading zeros are insignificant - note the difference from C, where a leading zero means octal.

  ld a, 99

Hexadecimal numbers are a sequence of hexadecimal digits (0..9 and A..F, case-insensitive), either prefixed or suffixed with an hexadecimal marker. If the marker is a suffix, and the number starts with a letter, then a leading zero has to be added.

  ld a, $FF
  ld a, 0xFF
  ld a, 0FFh

Binary numbers are a sequence of binary digits (0..1), either prefixed or suffixed with a binary marker.

  ld a, %11
  ld a, @11
  ld a, 0b11
  ld a, 11b

Binary numbers can be specified as bitmaps, with # as 1 and - as 0, using the binary prefix (@ or %) immediately followed by a double-quoted string of hashes and dashes.

  defb @"---##---"
  defb @"-##--##-"
  defb %"-##-----"
  defb %"-##-----"
  defb @"-##--##-"
  defb @"---##---"

Character constants

A character enclosed in single-quotes can be used to represent the character code.

  defb 'A'

ASMPC

ASMPC can be used in an expression to represent the address of the current instruction. The value will be resolved during linking.

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