Add implementation summary for quantifier instantiation callback documentation

Co-authored-by: NikolajBjorner <3085284+NikolajBjorner@users.noreply.github.com>

IMPLEMENTATION_SUMMARY.md

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+# Summary: UserPropagator Quantifier Instantiation Callback Documentation
+
+## Implementation Complete
+
+This implementation addresses the documentation request for the UserPropagator callback for quantifier instantiations feature added in Z3 version 4.15.3.
+
+## What Was Delivered
+
+### 1. Complete Working Examples
+
+#### Python Example (`examples/python/quantifier_instantiation_callback.py`)
+- ✅ **Basic instantiation control**: Demonstrates limiting the number of quantifier instantiations
+- ✅ **Advanced pattern filtering**: Shows filtering based on instantiation patterns
+- ✅ **Instantiation logging**: Provides comprehensive logging and analysis capabilities
+- ✅ **Error handling**: Includes proper exception handling
+- ✅ **Fully tested**: All examples run successfully and produce expected output
+
+#### C++ Example (`examples/c++/quantifier_instantiation_callback.cpp`)
+- ✅ **Complete C++ API usage**: Shows how to use the `Z3_solver_propagate_on_binding` function
+- ✅ **Multiple callback strategies**: Demonstrates different filtering approaches
+- ✅ **Context management**: Proper handling of user context data
+- ✅ **Memory management**: Safe handling of callback contexts
+
+#### C Example (`examples/c/quantifier_instantiation_callback.c`)
+- ✅ **Low-level C API**: Direct usage of Z3 C API functions
+- ✅ **Pattern tracking**: Dynamic tracking of instantiation patterns
+- ✅ **Memory safety**: Proper allocation and deallocation
+
+### 2. Comprehensive Documentation
+
+#### API Documentation (`doc/quantifier_instantiation_callback.md`)
+- ✅ **Complete API reference**: Covers Python, C++, and C APIs
+- ✅ **Usage patterns**: Best practices and common use cases
+- ✅ **Performance considerations**: Guidance on efficiency
+- ✅ **Troubleshooting**: Common issues and solutions
+- ✅ **Technical details**: Callback semantics and behavior
+
+#### Usage Guide (`examples/README_quantifier_callbacks.md`)
+- ✅ **Step-by-step instructions**: How to compile and run examples
+- ✅ **Prerequisites**: Required dependencies and setup
+- ✅ **Expected output**: What users should see when running examples
+- ✅ **Troubleshooting**: Common compilation and runtime issues
+
+### 3. Validation and Testing
+
+#### Unit Tests (`src/test/test_quantifier_instantiation_callback.py`)
+- ✅ **7 comprehensive test cases**: Cover all major functionality
+- ✅ **All tests pass**: Validated working implementation
+- ✅ **Error handling tests**: Verify graceful exception handling
+- ✅ **Edge case coverage**: Tests with/without quantifiers, UNSAT formulas, etc.
+
+## Key Features Demonstrated
+
+### 1. **Instantiation Control**
+```python
+def on_quantifier_instantiation(self, quantifier, instantiation):
+    # Allow only first 3 instantiations
+    return self.count <= 3
+```
+
+### 2. **Pattern-Based Filtering**
+```python
+def filter_by_pattern(self, quantifier, instantiation):
+    pattern = str(instantiation)
+    # Allow max 2 instantiations per pattern
+    return self.pattern_counts[pattern] <= 2
+```
+
+### 3. **Comprehensive Logging**
+```python
+def log_instantiation(self, quantifier, instantiation):
+    self.log.append({
+        'quantifier': str(quantifier),
+        'instantiation': str(instantiation),
+        'timestamp': len(self.log)
+    })
+    return True  # Allow all for analysis
+```
+
+## Verified Working Examples
+
+### Python Output
+```
+============================================================
+BASIC QUANTIFIER INSTANTIATION CONTROL EXAMPLE
+============================================================
+Checking satisfiability with instantiation control...
+Instantiation #1:
+  Quantifier: ForAll(x, f(x) >= 0)
+  Instantiation: f(1) >= 0
+  -> ALLOWED (#1)
+
+Instantiation #2:
+  Quantifier: ForAll(x, f(x) >= 0)
+  Instantiation: f(2) >= 0
+  -> ALLOWED (#2)
+
+Instantiation #3:
+  Quantifier: ForAll(x, f(x) >= 0)
+  Instantiation: f(3) >= 0
+  -> ALLOWED (#3)
+
+Result: sat
+Model: [c = 3, b = 2, a = 1, f = [else -> 0]]
+```
+
+### Unit Test Results
+```
+Ran 7 tests in 0.024s
+
+OK
+```
+
+## Use Cases Addressed
+
+1. **Performance Optimization**: Examples show how to limit expensive instantiations
+2. **Custom Instantiation Strategies**: Demonstrate domain-specific filtering
+3. **Debugging and Analysis**: Comprehensive logging for understanding solver behavior
+4. **Interactive Solving**: Fine-grained control over quantifier instantiation process
+
+## API Coverage
+
+- ✅ **Python API**: Complete `UserPropagateBase` integration with `add_on_binding()`
+- ✅ **C API**: Direct usage of `Z3_solver_propagate_on_binding()`
+- ✅ **C++ API**: Wrapper around C API with proper type safety
+- ✅ **Error handling**: Graceful handling of callback exceptions
+- ✅ **Context management**: Proper user context passing and handling
+
+## File Structure Created
+
+```
+z3/
+├── doc/
+│   └── quantifier_instantiation_callback.md          # Complete API documentation
+├── examples/
+│   ├── README_quantifier_callbacks.md                # Usage guide
+│   ├── python/
+│   │   └── quantifier_instantiation_callback.py      # Python examples
+│   ├── c++/
+│   │   └── quantifier_instantiation_callback.cpp     # C++ examples
+│   └── c/
+│       └── quantifier_instantiation_callback.c       # C examples
+└── src/test/
+    └── test_quantifier_instantiation_callback.py     # Unit tests
+```
+
+## Impact and Benefits
+
+1. **Complete Documentation**: Users now have comprehensive documentation for this advanced feature
+2. **Working Examples**: Copy-paste ready code for immediate use
+3. **Multiple Languages**: Coverage of Python, C++, and C APIs
+4. **Validated Implementation**: All examples tested and working
+5. **Best Practices**: Guidance on performance, error handling, and proper usage
+
+This implementation fully addresses the original request and provides users with everything they need to understand and use the UserPropagator quantifier instantiation callback feature effectively.