# Useful Functions

This chapter contains a summary of useful functions and subroutines that might be re-used in the future.

## General Functions and Subroutines

|   Function   |    Module     |     Input      |  Output   | Description                                                                                                |
| :----------: | :-----------: | :------------: | :-------: | :--------------------------------------------------------------------------------------------------------- |
| `UNITVECTOR` | `MOD_Globals` |   3D vector    | 3D vector | Normalizes a given vector by dividing all vectors entries by the vector's magnitude                        |
| `CROSSNORM`  | `MOD_Globals` | two 3D vectors | 3D vector | Computes the cross product of two 3-dimensional vectors: cross=v1 x v2 and normalizes the resulting vector |
|   `CROSS`    | `MOD_Globals` | two 3D vectors | 3D vector | Computes the cross product of two 3-dimensional vectors: cross=v1 x v2                                     |
| `VECNORM3D`  | `MOD_Globals` |   3D vector    |  `REAL`   | Computes the Euclidean norm (length) of a vector                                                           |
| `DOTPRODUCT` | `MOD_Globals` |   3D vector    |  `REAL`   | Computes the dot product of a vector with itself                                                           |

## Particle Functions and Subroutines

|                Function (Module)                 | Input                                                            |         Output         | Description                                                                                                                               |
| :----------------------------------------------: | :--------------------------------------------------------------- | :--------------------: | :---------------------------------------------------------------------------------------------------------------------------------------- |
|      `isChargedParticle` (`MOD_part_tools`)      | particle ID                                                      |       `LOGICAL`        | Check if particle has charge unequal to zero                                                                                              |
|         `PARTISELECTRON` (`MOD_globals`)         | particle ID                                                      |       `LOGICAL`        | Check if particle is an electron by checking if the charge is equal to 1.602176634e-19 (division and nearest integer)                     |
|      `isDepositParticle` (`MOD_part_tools`)      | particle ID                                                      |       `LOGICAL`        | Check if particle is to be deposited on the grid                                                                                          |
|       `isPushParticle` (`MOD_part_tools`)        | particle ID                                                      |       `LOGICAL`        | Check if particle is to be pushed (integrated in time)                                                                                    |
|    `isInterpolateParticle` (`MOD_part_tools`)    | particle ID                                                      |       `LOGICAL`        | Check if the field at a particle's is to be interpolated (accelerated)                                                                    |
|    `VeloFromDistribution` (`MOD_part_tools`)     | distribution type, Tempergy                                      |       3D vector        | **WIP**, Calculates a velocity vector from a defined velocity distribution and Tempergy (temperature [K] or energy [J] or velocity [m/s]) |
|       `DiceUnitVector` (`MOD_part_tools`)        | `None`                                                           |       3D vector        | Calculates a normalized vector in 3D (unit space) in random direction                                                                     |
| `DiceDeflectedVelocityVector` (`MOD_part_tools`) | cRela2(post-collison), alphaVSS(iSpecA,iSpecB)                   |       3D vector        | Calculates scaled post-collision relative velocity vector in center-of-mass frame                                                         |
|                                                  | if alphaVSS>1 (VSS) also: , cRelaX,cRelaY,cRelaZ (pre-collision) |                        | VSS case includes coordinate transformation due to anisotropic scattering                                                                 |
|       `CreateParticle` (`MOD_part_tools`)        | species ID, position, element ID, velocity and internal energies | particle ID (optional) | Creates a new particle at a given position and energetic state and return the new particle ID (optional)                                  |
|       `RemoveParticle` (`MOD_part_tools`)        | particle ID                                                      |                        | Removes the specified particle by setting all the required flags and deallocating internal data arrays                                    |
|      `GetParticleWeight` (`MOD_part_tools`)      | particle ID                                                      |         `REAL`         | Determines the weighting factor of a particle                                                                                             |