BITWISE.md

Bitwise Operators

Operators

Binary Bitwise Operators

• & - Bitwise AND
• | - Bitwise OR (pipe character)
• ^ - Bitwise XOR (caret)

Unary Bitwise Operator

• ~ - Bitwise NOT (tilde) - one's complement

Operator Precedence

Bitwise operators fall between comparison operators and arithmetic operators:

1. Unary: ! - ~ & *
2. Multiplicative: * / %
3. Additive: + -
4. Bitwise OR: |
5. Bitwise XOR: ^
6. Bitwise AND: &
7. Comparison: < <= > >= == !=
8. Logical AND: &&
9. Logical OR: ||

Assembly Implementation

All bitwise operations use 68000 long-word versions:

and.l d1,d0     ; Bitwise AND
or.l d1,d0      ; Bitwise OR
eor.l d1,d0     ; Bitwise XOR (exclusive or)
not.l d0        ; Bitwise NOT (one's complement)

Examples

Bit Masking

var status: long = 0;
var ENABLE_FLAG: long = 1;

// Set a flag
status = status | ENABLE_FLAG;

// Check if flag is set
if (status & ENABLE_FLAG) {
    // flag is set
}

// Clear a flag
status = status & ~ENABLE_FLAG;

Bit Extraction

var byte_value: long = 255;
var lower_nibble: long = byte_value & 15;    // Extract bits 0-3
var upper_nibble: long = (byte_value >> 4) & 15;  // Extract bits 4-7

Bit Toggling

var flags: long = 8;  // bit 3 set
flags = flags ^ 8;    // Toggle bit 3

Distinction from Address-Of

The & operator has two different meanings depending on context:

// Unary prefix: address-of
var ptr: long* = &my_variable;

// Binary infix: bitwise AND
var result: long = value & mask;

The parser disambiguates based on position:

• Prefix position (after operators like =, (, etc.) → address-of
• Infix position (between values) → bitwise AND

See examples/bitwise_test.has and examples/bitwise_comprehensive.has for more examples.