One of the many exciting new features in the upcoming Lean 4.22 release is a preview of the new verification infrastructure for proving properties of imperative programs. In this post, I’ll take a first look at this feature, show a simple example of what it can do, and compare it to similar tools.

A small scripting language.

• Dino aims to look like C language
• High-Level scripting object-oriented language:
  • Multi-precision integers
  • Heterogeneous extensible arrays, array slices
  • Associative tables with possibility to delete elements
  • Powerful and safe class composition operation for (multiple) inheritance and traits description
  • First class functions, classes, and fibers with closures, anonymous functions, classes, fibers
  • Exception handling
  • Concurrency
  • Pattern matching
  • Unicode 8 support

Developed ~32 years ago and revised a few times, last major revision ~9 years ago.

PL/I (pronounced "Programming Language 1") is a programming language that first appeared in 1964. It resembles BASIC and COBOL. This site is bare-bones and uses tables for layout (common before CSS).

However, this compiler is relatively new and still being maintained. v1.4.0 was released yesterday (it added support for array expressions), v1.0 was released in 2023, and development started in 2007.

I wanted to make a programming language that resembled magical circles. This is more like a way to write PostScript that looks like a magical circle, but I will refer to it as Mystical in this document.

Related: https://programming.dev/post/28438809

Rivulet is a programming language of flowing strands, written in semigraphic characters. A strand is not pictographic: its flow does not simulate computation. There are four kinds of strands, each with their own symbolism and grammatical rules. Together, they form glyphs, tightly-packed blocks of code whose strands execute together.

Here is a complete Fibonacci program:

   ╵──╮───╮╭─    ╵╵╭────────╮
    ╰─╯╰──╯│       ╰─╶ ╶╮╶╮╶╯
   ╰─────╮ │      ╭─────╯ ╰─────╮
         ╰─╯ ╷    ╰───       ───╯╷

   ╵╵─╮  ╭─╮     ╭──       ╵╵╰─╮  ──╮──╮
      ╰─╮│ ╰─╯ ╵╵╰─╯╶╮       ╴─╯  ╭─╯╭─╯
      ╰─╯╰─ ╰──╯╰────╯       ╭╴ ╵╶╯ ╶╯╶╮
        ╭─╮ ╭╴               │  ╰──────╯
        │ │ │                ╰─╮       ╭─╮
      │ │ ╰─╯                  │     │   │
      ╰─╯            ╷         ╰──── ╰───╯╷

   ╵╵ ╭──  ──╮  ╭─╮         ╵╰─╮
      ╰─╮  ╭─╯╭─╯ │          ╴─╯
       ╶╯╵╶╯  │ ╷╶╯          ╭─╮
     ╭─╮ ╰────╯ │   ╭─╮        │
     │ ╰────╮ ╭─╯ ╭╴│ │      ╭─╯
     ╰────╮ │ │ │ │ │ │      │
     ╭────╯ │ │ ╰─╯ │ ╷      ╰─╷
     ╰────╮ │ ╰─────╯ │
          │ ╰─────────╯╷

Target audience: Practitioners interested in programming language design and familiar with representations of errors in at least a few different languages such as error codes, checked/unchecked exceptions, tagged unions, polymorphic variants etc.

Estimated reading time: 60 to 90 mins.

Neut is a functional programming language with static memory management.

Its key features include:

• Full λ-calculus support
• Predictable automatic memory management
• The absence of annotations to the type system when achieving both of the above

Neut doesn't use GCs or regions. Instead, it takes a type-directed approach to handle resources.

A ~1 month old post about (sort-of) real-world experience from someone whose worked on a language as a hobby for 3 years.

The interesting part starts at https://vine.dev/docs/features/inverse

Discussion: https://news.ycombinator.com/item?id=43144040

After three years I feel like I'm qualified to give some general advice.

It will take much longer than you expect

Arenas, a.k.a. regions, are everywhere in modern language implementations. One form of arenas is both super simple and surprisingly effective for compilers and compiler-like things. Maybe because of its simplicity, I haven’t seen the basic technique in many compiler courses—or anywhere else in a CS curriculum for that matter. This post is an introduction to the idea and its many virtues.