# Missing Operators and Statements - COMPLETED

**Status:** ✅ DONE
**Priority:** MEDIUM
**Created:** 2025-10-31
**Completed:** 2025-10-31

## Summary

Successfully implemented EQV, IMP operators and RANDOMIZE statement that were parsed but not executed. All features verified against MBASIC 5.21 documentation and tested.

## Implementation Details

### Code Changes

**File: `src/interpreter.py`**

1. **Added `execute_randomize()` method** (lines 1417-1440):
   - Reseeds Python's `random` module
   - With seed: uses `random.seed(int(seed))`
   - Without seed: uses `random.seed(time.time())`

2. **Added EQV operator** (lines 2645-2649):
   - Implements logical equivalence: `A EQV B = NOT (A XOR B)`
   - Bitwise implementation: `~(int(left) ^ int(right))`

3. **Added IMP operator** (lines 2650-2654):
   - Implements logical implication: `A IMP B = (NOT A) OR B`
   - Bitwise implementation: `(~int(left)) | int(right)`

### Test Files Created

1. **`basic/dev/tests_with_results/test_eqv_imp.bas`** - Tests EQV and IMP operators
   - Truth table tests for both operators
   - Bitwise operation tests
   - All tests passing ✓

2. **`basic/dev/tests_with_results/test_randomize.bas`** - Tests RANDOMIZE statement
   - Specific seed tests (reproducibility)
   - Different seed tests
   - Expression as seed tests
   - Timer-based seed tests
   - All tests passing ✓

## Features Implemented

### 1. EQV Operator (Logical Equivalence)

**Final Status:**
- ✅ Lexer recognizes token: `TokenType.EQV`
- ✅ Parser creates AST node
- ✅ Interpreter implemented in `evaluate_binaryop()`
- ✅ Test suite created and passing

**Test:**
```basic
10 PRINT 5 EQV 3
20 END
```

**Action Items:**
1. **VERIFY:** Check MBASIC 5.21 manual/documentation for EQV operator
2. **VERIFY:** Test in real MBASIC 5.21 (see `tests/HOW_TO_RUN_REAL_MBASIC.md`)
3. If real: Implement `evaluate_binaryop()` handler for `TokenType.EQV`
4. If real: Add `test_eqv.bas` to test suite
5. If not real: Remove from lexer/parser, document as not in MBASIC 5.21

**Expected Behavior (if real):**
```
EQV is logical equivalence:
  -1 EQV -1 = -1  (TRUE EQV TRUE = TRUE)
  -1 EQV 0  = 0   (TRUE EQV FALSE = FALSE)
  0 EQV -1  = 0   (FALSE EQV TRUE = FALSE)
  0 EQV 0   = -1  (FALSE EQV FALSE = TRUE)
```

### 2. IMP Operator (Logical Implication)

**Final Status:**
- ✅ Lexer recognizes token: `TokenType.IMP`
- ✅ Parser creates AST node
- ✅ Interpreter implemented in `evaluate_binaryop()`
- ✅ Test suite created and passing

**Test:**
```basic
10 PRINT 5 IMP 3
20 END
```

**Action Items:**
1. **VERIFY:** Check MBASIC 5.21 manual/documentation for IMP operator
2. **VERIFY:** Test in real MBASIC 5.21 (see `tests/HOW_TO_RUN_REAL_MBASIC.md`)
3. If real: Implement `evaluate_binaryop()` handler for `TokenType.IMP`
4. If real: Add `test_imp.bas` to test suite
5. If not real: Remove from lexer/parser, document as not in MBASIC 5.21

**Expected Behavior (if real):**
```
IMP is logical implication (A IMP B means "if A then B"):
  -1 IMP -1 = -1  (TRUE IMP TRUE = TRUE)
  -1 IMP 0  = 0   (TRUE IMP FALSE = FALSE)
  0 IMP -1  = -1  (FALSE IMP TRUE = TRUE)
  0 IMP 0   = -1  (FALSE IMP FALSE = TRUE)
```

### 3. RANDOMIZE Statement

**Final Status:**
- ✅ Lexer recognizes keyword
- ✅ Parser creates `RandomizeStatementNode`
- ✅ AST node has seed parameter defined
- ✅ Interpreter implemented `execute_randomize()`
- ✅ Test suite created and passing

**Test:**
```basic
10 RANDOMIZE
20 PRINT RND
30 END
```

**Action Items:**
1. **VERIFY:** Check MBASIC 5.21 manual/documentation for RANDOMIZE
2. **VERIFY:** Test in real MBASIC 5.21 (see `tests/HOW_TO_RUN_REAL_MBASIC.md`)
3. If real: Implement `execute_randomize()` in interpreter
4. If real: Add `test_randomize.bas` to test suite
5. If not real: Remove from parser, document as not in MBASIC 5.21

**Expected Behavior (if real):**
```
RANDOMIZE          - Seed with current time/system value
RANDOMIZE seed     - Seed with specific value
```

**Note:** Currently programs use `PEEK(0)` for random seeding (returns random 0-255).

### ~~4. Random Access File Operations~~ ✅ IMPLEMENTED AND TESTED

**Status:** COMPLETE - Random access files are fully implemented!

**Implemented Statements:**
- ✅ `FIELD` - Define random access record structure
- ✅ `GET` - Read record from random access file
- ✅ `PUT` - Write record to random access file
- ✅ `LSET` - Left-justify string in field
- ✅ `RSET` - Right-justify string in field

**Test:** `basic/dev/tests_with_results/test_random_files.bas` - All tests passing!

## How to Verify in Real MBASIC 5.21

See: `tests/HOW_TO_RUN_REAL_MBASIC.md`

```bash
cd tests
cat > /tmp/test.bas << 'EOF'
10 PRINT "Testing EQV"
20 PRINT -1 EQV -1
30 PRINT -1 EQV 0
40 PRINT 0 EQV 0
50 SYSTEM
EOF

cat /tmp/test.bas | (cd mbasic521 && ./mbasic)
```

## Implementation Notes

### If Features Are Real:

For **EQV operator:**
```python
# In src/interpreter.py, evaluate_binaryop()
elif expr.operator == TokenType.EQV:
    # Logical equivalence: A EQV B = NOT (A XOR B)
    # In BASIC: -1 = TRUE, 0 = FALSE
    # Bitwise: invert XOR result
    return ~(left ^ right)
```

For **IMP operator:**
```python
# In src/interpreter.py, evaluate_binaryop()
elif expr.operator == TokenType.IMP:
    # Logical implication: A IMP B = (NOT A) OR B
    # In BASIC: -1 = TRUE, 0 = FALSE
    # Bitwise: (~A) | B
    return (~left) | right
```

For **RANDOMIZE:**
```python
# In src/interpreter.py
def execute_randomize(self, stmt):
    """Execute RANDOMIZE statement"""
    import random
    if stmt.seed:
        seed = self.evaluate_expression(stmt.seed)
        random.seed(int(seed))
    else:
        # Use timer/system value
        random.seed()
```

### If Features Are NOT Real:

1. Remove token definitions from `src/tokens.py`
2. Remove AST nodes from `src/ast_nodes.py`
3. Remove parser rules from `src/parser.py`
4. Document in a "Features NOT in MBASIC 5.21" section

## Success Criteria

1. **Verification complete** - Confirmed whether each feature is in MBASIC 5.21
2. **If real:** All features implemented and tested
3. **If not real:** All features removed from codebase
4. **Documentation updated** - Clear about what's in MBASIC 5.21 vs. not

## References

- MBASIC 5.21 manual: Check `docs/external/` for reference docs
- Real MBASIC testing: `tests/HOW_TO_RUN_REAL_MBASIC.md`
- Current test suite: `basic/dev/tests_with_results/`
- Parser implementation: `src/parser.py`
- Interpreter: `src/interpreter.py`

## Related Files

- Token definitions: `src/tokens.py`
- AST nodes: `src/ast_nodes.py`
- Parser: `src/parser.py`
- Interpreter: `src/interpreter.py`
- Existing logical operators test: `basic/dev/tests_with_results/test_logical_ops.bas`

---

**Created:** 2025-10-31
**Priority:** MEDIUM - Verify first before implementing
**Blocked by:** Need to verify these are actually in MBASIC 5.21 (not AI hallucination)
