# Getting Started

## Requirements

| Dependency | Version | Notes |
|---|---|---|
| CMake | ≥ 3.21 | |
| C++ compiler | GCC ≥ 11, Clang ≥ 13 | C++20 required |
| nanobind | ≥ 2.1 | auto-fetched; Python ≥ 3.8 |
| Catch2 | v3 | auto-fetched for tests |
| OpenCV | ≥ 4 | optional; only for examples 09/12/13 |

## Build

```bash
cmake -B build                          # core + tests + C++ examples
cmake --build build --parallel
ctest --test-dir build                  # run all tests including example smoke tests
```

Enable Python bindings:

```bash
cmake -B build -DKPN_BUILD_PYTHON=ON
cmake --build build --parallel
```

Skip examples:

```bash
cmake -B build -DKPN_BUILD_EXAMPLES=OFF
```

## Your first pipeline

Three functions — source, transform, sink — wired into a `Network`:

```cpp
--8<-- "examples/01_hello_pipeline/main.cpp:basic_node_fns"
```

Create nodes, connect them, build and run:

```cpp
--8<-- "examples/01_hello_pipeline/main.cpp:network_build"
```

That's it. Types are inferred from function signatures. The channel between `src` and `dbl` carries `int`; the channel between `dbl` and `prn` also carries `int`. A type mismatch is a compile error.

## Named ports

For nodes with multiple inputs or outputs, name the ports for clarity:

```cpp
--8<-- "examples/02_named_ports/main.cpp:named_port_creation"
```

Wire by name instead of index:

```cpp
--8<-- "examples/02_named_ports/main.cpp:named_port_network"
```

## Multi-output nodes

Return a `std::tuple` to fan out to multiple downstream nodes:

```cpp
--8<-- "examples/03_multi_output/main.cpp:multi_output_fn"
```

Wire each tuple element to its own downstream node:

```cpp
--8<-- "examples/03_multi_output/main.cpp:fanout_network"
```