<h1 align="center">SCSA Pseudocode Interpreter</h1> <p align="center"> <img src="https://img.shields.io/github/actions/workflow/status/SaintNong/pseudocode/ci.yml?branch=main&style=for-the-badge&logo=github&label=Build"> <img src="https://img.shields.io/github/actions/workflow/status/SaintNong/pseudocode/ci.yml?branch=main&style=for-the-badge&logo=cplusplus&label=Tests"> <img src="https://img.shields.io/badge/License-MIT-blue?style=for-the-badge"> <img src="https://img.shields.io/github/v/release/SaintNong/pseudocode?style=for-the-badge&label=Version&color=orange"> </p> <p align="center"> SCSA Pseudocode is a high-level object oriented interpreted language programming language. <br> It is based on the WA School Curriculum and Standards Authority's ATAR Computer Science <a href="https://senior-secondary.scsa.wa.edu.au/__data/assets/pdf_file/0003/1090875/Year-11_12_Computer-Science_ATAR_Additional-syllabus-support-booklet-.PDF">"Pseudocode" (2024)</a>. </p>

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"<em>This spec is so specific that it might as well be a real language...</em>"

This repository contains a full toolchain for Pseudocode development, including an interpreter written in C++, and a VSCode extension with highlighting and snippets.

Examples

Selection Sort in pseudocode (and syntax highlighting)!

Integrated command line REPL

User friendly error messages!

Installation

• Follow the Installation Guide to get started with the interpreter!

• If you only want Syntax Highlighting/Snippets then check out the VSCode Extension on the marketplace.

Features

• Handwritten Lexer with locatable tokens
• Recursive descent parser for statements/blocks
• Pratt Parser for parsing expressions with operator precedence
• Working tree walk interpreter
  • Shared pointers for garbage collection
  • Variable scopes
• Native Functions API
• Good error reporting which is anchored to nearest token for easy debugging
• Visual Studio Code Highlighting Extension
• Integration tests
• Circular inheritance check

Supported Pseudocode Language Features

• Basic datatypes and a dynamic typing system
  • [int, float, string, bool, Null]
  • Functions and instances as variables
• Local/Global scope separation
• Standard Library Functions:
  • PRINT(...args): Prints values followed by a newline.
  • OUTPUT(...args): Prints values without a trailing newline.
  • INPUT(prompt?): Reads a line of input from the user.
  • INT(value): Converts a value to an integer.
  • FLOAT(value): Converts a value to a float.
  • STRING(value): Converts a value to its string representation.
  • BOOL(value): Converts a value to a boolean.
  • RANDOM(min, max): Returns a random integer between min and max.
  • TIME(): Returns current system time in seconds.
  • TYPE(value): Returns the type of the value as a string.
• Binary operations/comparisons [+, -, *, /, >, <, >=, <=, ==, !=]
• Logical operators [AND, OR, NOT]
• While, For-In, For-To, and Repeat-Until loops
• If, If-Else and Else-If statements
• Functions
• CASE statements
  • Multiple conditions can be checked by a single branch by separating them with commas
  • Case branches with multi line statements are supported
• Strings
  • string[i] Indexes into a string
  • string.length Returns the length of a string
  • string.slice(a, b) Returns the substring from index a to b (inclusive)
  • Multiplication is supported (0 and negative return empty string)
• Arrays
  • array[i] Indexes into an array
  • array.slice(a, b) Returns a shallow copy from index a to b (inclusive)
  • array.append(x) Appends value to the end of the array
  • array.length Returns length of the array as an integer
  • Multiplication is supported (0 and negative return empty array)
• Object Oriented Programming✨✨
  • Syntax requires 'this' to reference object attributes/methods which is technicaly not SCSA standard
  • this.super() is used to call parent constructor/methods/fields (it can be chained)
  • Encapsulation works
  • Object methods work
  • Inheritance works
  • Circular inheritance is checked

Integration Tests

This project uses a small custom Python test harness integrated with CTest for CI/CD. Tests execute .scsa files and check that the interpreter output matches what is expected in the comments. To run the test suite:

1. Build the project (see installation)
2. Run the tests from the /tests directory

# Runs the integration tests
python3 tester.py <path-to-your-binary>

Environment Variables

The interpreter supports the following environment variables:

• NO_COLOR: If set, suppresses all ANSI escape sequences for color output. Follows the NO_COLOR informal standard.

Other stuff

Currently WIP Features

• Dictionary datatype

Future Plans

• Integrated file IO in standard library
• Subprocess in standard library
• Custom Bytecode VM which requires:
  • Custom stack-based bytecode
  • Bytecode compiler
  • Bytecode virtual machine
  • Some bytecode optimisation
• Manual garbage collector (reference based)

Credits

• Crafting Interpreters by Robert Nystrom
  • This book is an excellent start to writing interpreters, and was massively helpful for starting this project
• tombl's scsa-pseudocode
  • In highschool when my friends joked about making an interpreter, to our surprise some legend had already done it before, in Node.js of all languages!
  • This project is excellent, but is based on an older specification of pseudocode without OOP and when variable assignment was done with arrows

Disclaimer

[!NOTE] I am not affiliated with SCSA in any way. The SCSA logo is being used in this context in an educational setting without any commercial purpose (it's MIT Licensed). If someone at SCSA is unhappy with this usage they should contact me via email, or an issue on the attached GitHub repository and I will remove it immediately. All other material such as the language specification is derived from the Australian curriculum, and is thus under CC4 BY.