# Design by Contract
Demonstrates the three pillars of aprender's contract system:
1. **Tensor layout contract** -- shape validation for GGUF to APR conversion
2. **Block size constants** -- quantization format invariants
3. **Contract error handling** -- typed errors for violations
## Run
```bash
cargo run --example design_by_contract
```
## Source
```rust,ignore
{{#include ../../../examples/design_by_contract.rs}}
```