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Expression Tree Calculator

Scala Versions (2008-19)

These Scala programs are from the chapter Notes on Scala for Java Programmers [1] (as HTML) (as PDF).

• Recursive function version using case classes ExprCase.scala

• Traditional object-oriented version ExprObj.scala

Python versions (2018)

Object-oriented versions

• Basic OO version ExprOO2.py

• OO versions using abstract base classes

  TODO: In the following, I seem to have been exploring various OO approaches. These need to be reexamined to determine which should be included here. In some of these, I was also exploring dataclasses and type annotations.

  • Using inheritance ExprABC2.py

  • Using registration and class methods ExprABC_RegClassmeth2.py

  • Using registration and mixin ExprABC_RegMixin2.py

  • Using registration and delegation ExprABC_RegDelegate2.py

  • Using dataclass decorators and type annotations ExprDC.py

Functional module versions

• Basic module of functions ExprFuncMod2.py

• Using dataclass decorators and type annotations ExprFuncMod2.py

• Using table (dictionary) of functions ExprEvalTab.py

Expression tree parser

These programs require the Python package Parsita, a parser combinator library similar to Scala’s.

TODO: These are not complete. At least a test driver is needed.

• Abstract syntax tree calc_ast2.py adapted and extended to work with Calculator expression parser – uses frozen data classes

• Parser calc_parser.py – uses Parsita combinator-based parser for simple Calculator-like language including function calls

Lua Versions (2013-16)

Recursive function versions (2013, 2014)

• Lua Recursive Functions with Record Representation exprRecFuncRecord.lua

• Lua Recursive Functions with List Representation exprRecFuncList2.lua

• Lua Evaluation Function Table with List Representation exprEvalTable2.lua

Object-oriented versions (2013, 2016)

• Lua Prototype Object-Based exprObjBased.lua

• Lua Object-Oriented with Inheritance

LPEG parsers (2013)

These programs require installation of a compatible LPEG library.

• Parser with captures exprParser.lua

• Parser with semantic actions exprParserSemantic.lua

Haskell Version (2017)

• Expression Tree Calculator case study
  • as HTML
  • as PDF
  • Haskell source

Acknowledgements

What I call the “recursive function version using case classes” is more or less the first version of these examples. It is closely based on the example in an early version of the Schinz and Haller tutorial [3]. I modified that version and also created the “traditional object-oriented version” for an assignment in the prototype offering of the Multiparadigm Programming course. I subsequently developed the Lua versions in 2013, the Haskell version in 2017, and the Python versions in 2018 for that or other courses. The Expression Tree is one of the examples or assignments I redesign and implement when I am learning and teaching a new language or want an assignment of that nature.

This example has been more or less expanded into the ELI Calculator Language introduced in several chapters of Exploring Languages with Interpreters and Functional Programming (ELIFP) [2].

I retired from the full-time faculty in May 2019. As one of my post-retirement projects, I am continuing work on possible textbooks based on the course materials I had developed during my three decades as a faculty member. In January 2022, I began refining the existing content, integrating separately developed materials together, reformatting the documents, constructing a unified bibliography (e.g., using citeproc), and improving my build workflow and use of Pandoc.

I maintain this chapter as text in Pandoc’s dialect of Markdown using embedded LaTeX markup for the mathematical formulas and then translate the document to HTML, PDF, and other forms as needed.

References