Package org.orekit.utils.units

Class Parser

java.lang.Object
org.orekit.utils.units.Parser
public class Parser extends Object
Parser for units.

This fairly basic parser uses recursive descent with the following grammar, where '*' can in fact be either '*', '×', '.', or '·', '/' can be either '/' or '⁄' and '^' can be either '^', "**" or implicit with switch to superscripts, and fraction are either unicode fractions like ½ or ⅞ or the decimal value 0.5. The special cases "n/a" returns a null list. It is intended to manage the special unit Unit.NONE. 

   unit         ::=  "n/a" | chain
   chain        ::=  operand { ('*' | '/') operand }
   operand      ::=  integer | integer term | term
   term         ::=  '√' base | base power
   power        ::=  '^' exponent | ε
   exponent     ::=  'fraction'   | integer | '(' integer denominator ')'
   denominator  ::=  '/' integer  | ε
   base         ::=  identifier | '(' chain ')'

This parses correctly units like MHz, km/√d, kg.m.s⁻¹, µas^⅖/(h**(2)×m)³, km/√(kg.s), √kg*km** (3/2) /(µs^2*Ω⁻⁷), km**0.5/s, #/y, 2rev/d², 1/s.

Note that we don't accept combining square roots and power on the same operand; km/√d³ is refused (but km/√(d³) is accepted). We also accept a single integer prefix and only at the start of the specification.

Since:
11.0
Author:
Luc Maisonobe

  • Method Details

    • buildTermsList

      public static List<PowerTerm> buildTermsList(String unitsSpecification)
      Build the list of terms corresponding to a units specification.
      Parameters:
      unitsSpecification - units specification to parse
      Returns:
      parse tree