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TRURL is a class library for Object Pascal supporting the creation of virtual calculators with reverse Polish notation (RPN). It comes with demo projects and several ready-to-use calculators for macOS, Linux and Windows.

TRURL is an acronym for "TRURL is a Reusable Universal RPN Library".

Class libraries

Currently, TRURL contains two independent class libraries:

  • RPN Engine: This is a full-featured calculation engine as a basis for Pascal-based RPN calculators
  • Segmitator: Library for virtual seven-segment displays (may be used independently of the RPN Engine)


The following applications are available from the TRURL project:

  • TRURL A: Simple demo app for the RPN Engine
  • TRURL G: Desktop RPN calculator inspired by the user interface of the DSKY unit of the Apollo Guidance Computer (AGC)

Additional calculators may be available from third parties

External links

All software is available with a BSD license from