selen 0.15.5

Constraint Satisfaction Problem (CSP) solver
Documentation 
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# Option 4 Complete: Simple Reified Methods Added to Model

## ✅ Task Complete

Successfully added 6 reified constraint methods to the Model struct for API consistency.

## What Was Done

### 1. Added Model Methods (`src/constraints/api/reified.rs`)
```rust
impl Model {
    pub fn eq_reif(&mut self, x: VarId, y: VarId, b: VarId);  // b ⇔ (x == y)
    pub fn ne_reif(&mut self, x: VarId, y: VarId, b: VarId);  // b ⇔ (x != y)
    pub fn lt_reif(&mut self, x: VarId, y: VarId, b: VarId);  // b ⇔ (x < y)
    pub fn le_reif(&mut self, x: VarId, y: VarId, b: VarId);  // b ⇔ (x <= y)
    pub fn gt_reif(&mut self, x: VarId, y: VarId, b: VarId);  // b ⇔ (x > y)
    pub fn ge_reif(&mut self, x: VarId, y: VarId, b: VarId);  // b ⇔ (x >= y)
}
```

### 2. Added Tests (`tests/test_reified_methods.rs`)
- Compilation tests for all methods
- Integer variable tests
- Float variable tests
- ✅ All passing

### 3. Documentation
- Created `docs/REIFIED_METHODS_ADDED.md` with complete details
- Full docstrings with examples for each method
- Backwards compatibility notes

## Benefits

| Aspect | Improvement |
|--------|-------------|
| **Consistency** | All constraint types now have Model methods |
| **Ergonomics** | `model.eq_reif(x, y, b)` vs `eq_reif(&mut model, x, y, b)` |
| **Discoverability** | IDE autocomplete shows methods |
| **Backwards Compatible** | Old function API still works |

## Testing Results

```
cargo test --release --lib
test result: ok. 291 passed; 0 failed; 1 ignored

cargo test --release --test test_reified_methods
test result: ok. 2 passed; 0 failed; 0 ignored
```

## API Consistency - Now Complete! 🎉

| Constraint Category | Model Methods | Status |
|-------------------|---------------|---------|
| Linear | `lin_eq`, `lin_le`, `lin_ne` | ✅ |
| Linear Reified | `lin_eq_reif`, `lin_le_reif`, `lin_ne_reif` | ✅ |
| **Simple Reified** | **`eq_reif`, `ne_reif`, `lt_reif`, `le_reif`, `gt_reif`, `ge_reif`** | ✅ **NEW!** |
| Boolean Linear | `bool_lin_eq`, etc. | ✅ |

## Code Impact

- **Lines Added**: ~170 (including docs)
- **Files Modified**: 1 (`src/constraints/api/reified.rs`)
- **Files Created**: 2 (test + doc)
- **Breaking Changes**: None
- **Performance Impact**: None (zero-cost delegation)

## Usage Example

```rust
use selen::prelude::*;

let mut model = Model::default();
let x = model.int(1, 10);
let y = model.int(1, 10);
let is_equal = model.bool();
let is_less = model.bool();

// New Model methods - clean and discoverable!
model.eq_reif(x, y, is_equal);  // is_equal ⇔ (x == y)
model.lt_reif(x, y, is_less);   // is_less ⇔ (x < y)

// Can now use boolean logic with these
let both = model.bool();
model.bool_and(is_equal, is_less, both);
```

## Next Steps (from original list)

Option 4 ✅ **DONE**

Remaining options:
1. SIMPLEX Phase I/II optimization (most critical for large problems)
2. External solver integration (pragmatic solution)
3. Sparse matrix representation (foundation work) - **user decided not to pursue**
5. Problem size heuristics (safety net)

## Time Investment

- Implementation: ~15 minutes
- Testing: ~5 minutes  
- Documentation: ~10 minutes
- **Total: ~30 minutes**

**ROI**: High - API consistency with minimal effort ✅

---

**Date**: October 10, 2025  
**Status**: Complete and merged  
**Tests**: All passing  
**Documentation**: Complete