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OPERATORS.md

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Operators Implemented

Arithmetic Operators

  • + - Addition
  • - - Subtraction
  • * - Multiplication (signed 16-bit muls.w)
  • / - Division (placeholder - returns 0)
  • % - Modulo (via divs.w, remainder in upper word)

Comparison Operators (all signed)

  • == - Equal (returns 1 or 0)
  • != - Not equal
  • < - Less than
  • <= - Less than or equal
  • > - Greater than
  • >= - Greater than or equal

Comparison results are:

  • 1 (true) if condition holds
  • 0 (false) if condition doesn't hold

Logical Operators

  • && - Logical AND (both operands must be non-zero)
  • || - Logical OR (at least one operand must be non-zero)
  • ! - Logical NOT (unary prefix)

Logical results are:

  • 1 (true) if condition holds
  • 0 (false) if condition doesn't hold

Unary Operators

  • - - Negation (prefix)
  • ! - Logical NOT (prefix)
  • & - Address-of
  • * - Dereference

Operator Precedence (highest to lowest)

  1. Unary: ! - & *
  2. Multiplicative: * / %
  3. Additive: + -
  4. Comparison: < <= > >=
  5. Equality: == !=
  6. Logical AND: &&
  7. Logical OR: ||

Assembly Implementation

Comparison Operators

Use 68000 cmp instruction with set conditional byte:

cmp.l d1,d0
seq d0      ; set d0 to 0xFF if equal, 0 otherwise
and.l #0xFF,d0
neg.b d0    ; convert 0xFF to 0x01, 0 stays 0

Logical Operators

Use conditional branches for short-circuit evaluation:

; a && b
tst.l d0
beq.s .false
tst.l d1
beq.s .false
move.l #1,d0
bra.s .done
.false:
move.l #0,d0
.done:

Modulo

Use 68000 divs.w and swap to get remainder:

divs.w d1,d0
swap d0      ; remainder is now in lower word
ext.l d0     ; sign-extend

Examples

See examples/operators_test.has for comprehensive operator examples.