**number(X)** |
succeeds if **X** is a number |

**const(X)** |
succeeds if **X** is instantiated with a constant (single
letter or single character) |

**var(X)** |
succeeds if **X** is a not-instantiated variable |

**integer(X)**
**R is integer(X)** |
checks whether **X** is an integer or converts it to
integer |

**float(X)**
**R is float(X)** |
checks whether **X** is a float or converts it to float |

**R is round(X)** |
returns in **R** an integer rounded from **X** |

**R is ceiling(X)** |
returns in **R** the first integer which is bigger than
**X** |

**R is floor(X)** |
returns in **R** , the last integer which is smaller
than **X** |