# Getting started

## Requirements

Requirements for NSL are mainly driven by NAIA:

* A C++ compiler with full c++17 support (tested with gcc >= 9.3.0)
* CMake version >= 3.13
* A ROOT installation compiled with c++17 support (tested with ROOT >= 6.22/08, recommended 6.26/02)

If you are working in an environment with a functioning NAIA install you should be good to go.


## Building and installing

Follow this simple procedure:

- Clone this repository
  - `git clone https://:@gitlab.cern.ch:8443/ams-italy/nsl.git` (Kerberos)
  - `git clone ssh://git@gitlab.cern.ch:7999/ams-italy/nsl.git` (SSH)
  - `git clone https://gitlab.cern.ch/ams-italy/nsl.git` (HTTPS)

- Create a build and install directory
  - e.g: `mkdir nsl.build nsl.install`

- Build the project (assuming the `NAIADIR` environment variable is set)
  - `cd nsl.build`
  - `cmake ../nsl -DCMAKE_INSTALL_PREFIX=${your-install-path-here}`
  - `make all install`

````{note}
If you don't have the ``NAIADIR`` variable set but you have a NAIA installation you can point CMake to it:

```bash
cmake ../nsl -DNAIA_DIR=${your-naia-install-path-here}/cmake
```

Alternatively you can have CMake download NAIA for you: 

```bash
cmake ../nsl -DNSL_DOWNLOAD_NAIA=ON -DNAIA_DOWNLOAD_VERSION=1.1.0
```

In the last example you can omit the NAIA version, a default version (which should be fairly recent) will be downloaded
````

## Using the project

To use the NAIA ntuples your project needs:

- the headers in `nsl.install/include`
- the `nsl.install/lib/libNSLSelections.so` library

Similarly to what NAIA does, NSL exports the `NSL::NSLSelections` CMake target which is the main one to link against.


```cmake
find_package(NSL REQUIRED)

set(SOURCES MyProgram.cpp)

add_executable(MyProgram ${SOURCES})
target_link_libraries(MyProgram NAIA::NAIAChain NSL::NSLSelections)
```

```{note}
For any question or in case you need help write to valerio.formato@cern.ch 
```