# BEAST v2.6.7 Documentation: beast.math.statistic.RPNcalculator

BEASTObject that performs calculations based on the State.

RPN calculator to evaluate simple expressions of parameters (Reverse Polish notation is a mathematical notation wherein every operator follows its operands)

Logable: yes, this can be used in a log.

## Inputs:

expression, parameter, argnames

expression
type: java.lang.String |

Expressions needed for the calculations |

Required input |

parameter
type: beast.core.Function*** |

Parameters needed for the calculations |

Optional input |

argnames
type: java.lang.String |

names of arguments used in expression (comma delimited), order as given by XML |

Optional input |