Interpreter: Add array operators and fix critical bugs

[fglock]

Summary

Implements comprehensive array operator support in the interpreter and fixes two critical bugs that were blocking progress.

Array Operators Implemented

• push/pop: Add/remove elements from end of array
• shift/unshift: Add/remove elements from beginning of array
• splice: Remove/insert elements at any position
• grep: Filter array elements with code block
• map: Transform array elements with code block
• sort: Sort array elements with comparison block
• reverse: Reverse array order
• split: Split string into array
• Array slice: Access multiple elements (@array[indices])
• Array slice assignment: Modify multiple elements at once
• Array element assignment: Single element modification ($array[n] = value)
• Multidimensional arrays: Support for @array[$x][$y]

Critical Bugs Fixed

1. Infinite Loop in Bare Blocks

Issue: Bare blocks { my @a = (1,2,3); } created infinite loops

Root Cause: BytecodeCompiler ignored For3Node.isSimpleBlock flag, always generating loop bytecode with GOTO back to start

Fix: Check isSimpleBlock flag and execute body once without loop structure

Impact: Bare blocks now execute correctly without hanging

2. Disassembler Index Out of Bounds

Issue: ./jperl --interpreter --disassemble failed with "Index 89 out of bounds for length 3"

Root Cause: SLOW_OP switch statement had default case that didn't skip operands, causing PC misalignment

Fix: Added disassembler cases for all new SLOW_OP operations:

• SLOWOP_SPLICE
• SLOWOP_ARRAY_SLICE
• SLOWOP_REVERSE
• SLOWOP_ARRAY_SLICE_SET
• SLOWOP_SPLIT

Each case now properly reads and skips all operands.

Impact: Disassembler works correctly for all bytecode

Known Issue (Not Addressed)

Array element access in function arguments returns wrong value:

my @arr = (1, 2, 3);
is($arr[1], 2, "test");  # gets: 1 instead of 2

Workaround: Assign to variable first:

my $x = $arr[1];
is($x, 2, "test");  # works correctly

Root Cause: ARRAY_SIZE opcode called after ARRAY_GET in scalar context for function arguments. This is a separate issue that will be addressed in a follow-up PR.

Files Modified

• Opcodes.java: Added SLOWOP_REVERSE, SLOWOP_ARRAY_SLICE_SET, SLOWOP_SPLIT
• BytecodeCompiler.java: Fixed For3Node.isSimpleBlock handling, added array operator compilation
• BytecodeInterpreter.java: Implemented array operation opcodes
• InterpretedCode.java: Added disassembler support for new SLOW_OP operations
• SlowOpcodeHandler.java: Implemented handlers for reverse, array slice set, split
• RuntimeArray.java: Added setSlice() method
• SKILL.md: Documented debugging patterns and critical lessons learned

Testing

All array operators tested with:

./jperl --interpreter src/test/resources/unit/array.t

Most array.t tests now pass. Remaining failures are due to the known scalar context issue in function arguments.

Commits

1. Add interpreter support for array operators and update SKILL.md
2. Add interpreter support for array slices, += operator, and % modulus
3. Add missing arithmetic opcodes to disassembler
4. Implement grep, map, and sort operators in interpreter
5. Implement reverse operator in interpreter
6. Implement array slice assignment in interpreter
7. Implement array element and multidimensional array assignment
8. Implement split operator in interpreter
9. Fix disassembler for new SLOW_OP opcodes (CRITICAL)
10. Fix infinite loop in bare blocks with isSimpleBlock flag (CRITICAL)
11. Document critical debugging patterns from array operators work

🤖 Generated with Claude Code