# Selen - CSP Solver
[](https://crates.io/crates/selen)
[](https://docs.rs/selen)
[](https://opensource.org/licenses/MIT)
A Constraint Satisfaction Problem (CSP) solver library written in Rust with zero external dependencies.
## Overview
This library provides efficient algorithms and data structures for solving constraint satisfaction problems. CSPs are mathematical problems defined as a set of objects whose state must satisfy a number of constraints or limitations.
**Variable Types**: `int`, `float`, mixed constraints
**Unbounded Variables**: Automatic bound inference for `int(i32::MIN, i32::MAX)` and `float(f64::NEG_INFINITY, f64::INFINITY)` - bounds inferred from context or sensible defaults
**Constraint Categories**:
- **Mathematical**: `+`, `-`, `*`, `/`, `%`, `abs()`, `min()`, `max()`, `sum()`
- **Comparison**: `==`, `!=`, `<`, `<=`, `>`, `>=` (natural syntax)
- **Boolean Logic**: `and()`, `or()`, `not()` with array syntax `and([a,b,c])` and variadic syntax `and(a,b,c,d)`
- **Global**: `alldiff()`, `allequal()`, element `x[y] = z`, `count(vars, value, count)`, `table(vars, tuples)`
- **Ordering**: `a <= b <= c`, `a < b < c`, `a >= b >= c`, `a > b > c` (natural `between` constraints)
- **Cardinality**: `at_least(vars, value, count)`, `at_most(vars, value, count)`, `exactly(vars, value, count)`
- **Conditional**: `if_then(condition, constraint)`, `if_then_else(condition, then_constraint, else_constraint)`
**Programmatic version of constraints**
```rust
m.new(x.lt(y)); // x < y
m.new(y.le(z)); // y <= z
m.new(z.gt(5)); // z > 5
m.new(x.add(y).le(z)); // x + y <= z
m.new(y.sub(x).ge(0)); // y - x >= 0
m.new(x.mul(y).eq(12)); // x * y == 12
m.new(z.div(y).ne(0)); // z / y != 0
```
**Mathematical syntax with post! macro**
```rust
post!(m, x < y); // x < y
post!(m, y <= z); // y <= z
post!(m, z > int(5)); // z > 5
post!(m, x + y <= z); // x + y <= z
post!(m, y - x >= int(0)); // y - x >= 0
post!(m, x * y == int(12)); // x * y == 12
post!(m, z / y != int(0)); // z / y != 0
```
**FlatZinc/MiniZinc Support**
For FlatZinc `.fzn` file support, use the separate [Zelen](https://github.com/radevgit/zelen) crate.
## Installation
Add this to your `Cargo.toml`:
```toml
[dependencies]
selen = "0.9"
```
## Examples
```
🧩 Solving Platinum Blonde puzzle:
📊 Puzzle stats: 17 clues given, 64 empty cells
Puzzle: Solution:
┌───────┬───────┬───────┐ ┌───────┬───────┬───────┐
│ · · · │ · · · │ · · · │ │ 9 8 7 │ 6 5 4 │ 3 2 1 │
│ · · · │ · · 3 │ · 8 5 │ │ 2 4 6 │ 1 7 3 │ 9 8 5 │
│ · · 1 │ · 2 · │ · · · │ │ 3 5 1 │ 9 2 8 │ 7 4 6 │
├───────┼───────┼───────┤ ├───────┼───────┼───────┤
│ · · · │ 5 · 7 │ · · · │ │ 1 2 8 │ 5 3 7 │ 6 9 4 │
│ · · 4 │ · · · │ 1 · · │ │ 6 3 4 │ 8 9 2 │ 1 5 7 │
│ · 9 · │ · · · │ · · · │ │ 7 9 5 │ 4 6 1 │ 8 3 2 │
├───────┼───────┼───────┤ ├───────┼───────┼───────┤
│ 5 · · │ · · · │ · 7 3 │ │ 5 1 9 │ 2 8 6 │ 4 7 3 │
│ · · 2 │ · 1 · │ · · · │ │ 4 7 2 │ 3 1 9 │ 5 6 8 │
│ · · · │ · 4 · │ · · 9 │ │ 8 6 3 │ 7 4 5 │ 2 1 9 │
└───────┴───────┴───────┘ └───────┴───────┴───────┘
✅ Solution found in 2289.885ms!
📊 Statistics: 538 propagations, 25 nodes explored
🔍 Efficiency: 21.5 propagations/node
```
### Core Problems
```bash
cargo run --release --example sudoku # Classic 9x9 Sudoku solver
cargo run --release --example n_queens # N-Queens backtracking
cargo run --release --example send_more_money # Cryptarithmetic puzzle
cargo run --release --example graph_coloring # Graph constraint problems
cargo run --release --example zebra_puzzle # Logic puzzle solving
```
### Constraint Types
```bash
cargo run --release --example constraint_global # AllEqual, Count, AllDiff
cargo run --release --example constraint_element # Element constraint usage
cargo run --release --example constraint_table # Table constraints
cargo run --release --example constraint_boolean # Boolean arrays and logic
```
### Advanced Features
```bash
cargo run --release --example advanced_runtime_api # Dynamic constraint building
cargo run --release --example advanced_memory_limits # Memory management demo
cargo run --release --example advanced_timeout # Timeout handling
```
### Real Applications
```bash
cargo run --release --example app_manufacturing # Industrial optimization
cargo run --release --example app_portfolio # Financial modeling
cargo run --release --example app_resource_allocation # Resource planning
```
### Basic Usage
```rust
use selen::prelude::*;
fn main() {
let mut m = Model::default();
// Create variables
let x = m.int(1, 10); // Integer variable from 1 to 10
let y = m.int(5, 15); // Integer variable from 5 to 15
// Add constraints
post!(m, x < y); // x must be less than y
post!(m, x + y == int(12)); // x + y must equal 12
// Solve the problem
if let Ok(solution) = m.solve() {
println!("x = {:?}", solution[x]); // x = ValI(1)
println!("y = {:?}", solution[y]); // y = ValI(11)
}
}
```
### Programmatic API Example
For developers who prefer a more explicit, programmatic approach, the same constraints can be built using the runtime API:
```rust
use selen::prelude::*;
fn main() {
let mut m = Model::default();
// Create variables
let x = m.int(1, 10);
let y = m.int(5, 15);
// Add constraints using programmatic API
m.new(x.lt(y)); // x < y
m.new(x.add(y).eq(12)); // x + y == 12
// Global constraints
let vars = vec![m.int(1, 5), m.int(1, 5), m.int(1, 5)];
m.alldiff(&vars.clone()); // All different
// Mathematical functions
let abs_result = m.abs(x);
m.new(abs_result.ge(1)); // abs(x) >= 1
// Solve the problem
if let Ok(solution) = m.solve() {
println!("x = {:?}", solution[x]);
println!("y = {:?}", solution[y]);
}
}
```
## License
This project is licensed under the MIT License - see the [LICENSE](LICENSE) file for details.