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:

 undefined

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

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

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

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.

Background: the authors are developing a static analysis library (or perhaps framework) called Codex and publishing papers on it. This post summarizes their most recent paper, which got accepted to OOPSLA 2024. The full paper and an artifact (Docker container) are both linked, and Codex is on GitHub with a demo.

Excerpt:

One of the main challenges when analyzing C programs is the representation of the memory. The paper proposes a type system, inspired by that of C, as the basis for this abstraction. While initial versions of this type system have been proposed in VMCAI'22 and used in RTAS'21, this paper extends it si

The language itself: https://crystal-lang.org/. Crystal is heavily inspired by Ruby but with static typing and native compilation (via LLVM). To make up for not being dynamic like Ruby, it has powerful global type inference, meaning you're almost never required to explicitly specify types. The linked "Notes on..." page gives much more details.

Abstract:

A computer program describes not only the basic computations to be performed on input data, but also in which order and under which conditions to perform these computations. To express this sequencing of computations, programming language provide mechanisms called control structures. Since the "goto" jumps of early programming languages, many control structures have been deployed: conditionals, loops, procedures and functions, exceptions, iterators, coroutines, continuations… After an overview of these classic control structures and their historical context, the course develops a more modern approach of control viewed as an object that programs can manipulate, enabling programmers to define their own control structures. Started in the last century by early work on continuations and the associated control operators, this approach was recently renewed through the theory of algebraic effects and its applications to user-defined effects and effect handlers in languages such a

Background: What are denotational semantics, and what are they useful for?

Also: Operational and Denotational Semantics

Denotational semantics assign meaning to a program (e.g. in untyped lambda calculus) by mapping the program into a self-contained domain model in some meta language (e.g. Scott domains). Traditionally, what is complicated about denotational semantics is not so much the function that defines them; rather it is to find a sound mathematical definition of the semantic domain, and a general methodology of doing so that scales to recursive types and hence general recursion, global mutable state, exceptions and concurrency¹².

In this post, I discuss a related is

This presents a method to reduce the overhead of the garbage collector, in a language with multi-stage programming (specifically two-level type theory) using regions.

Introduction:

Back in August, Murat Derimbas published a blog post about the paper by Herlihy and Wing that first introduced the concept of linearizability. When we move from sequential programs to concurrent ones, we need to extend our concept of what "correct" means to account for the fact that operations from different threads can overlap in time. Linearizability is the strongest consistency model for single-object systems, which means that it's the one that aligns closest to our intuitions. Other models are weaker and, hence, will permit anomalies that violate human intuition about how systems should behave.

Beyond introducing linearizability, one of the things that Herlihy and Wing do in this pape

Key Features

• Multiple types (number, bool, datetime, string and error)
• Memory managed by user (no allocs)
• Iterator based interface
• Supporting variables
• Stateless
• Expressions can be compiled (RPN stack)
• Fully compile-time checked syntax
• Documented grammar
• Standard C11 code
• No dependencies

Examples

 c

    
# Numerical calculations
sin((-1 + 2) * PI)

# Dates
datetrunc(now(), "day")

# Strings
"hi " + upper("bob")  + trim("  !  ")

# Conditionals
ifelse(1 < 5 && length($alphabet) > 25, "case1", "case2")

# Find the missing letter
replace($alphabet, substr($alphabet, 25 - random(0, length($alphabet)), 1), "")

  

From homepage:

Hy (or "Hylang" for long) is a multi-paradigm general-purpose programming language in the Lisp family. It's implemented as a kind of alternative syntax for Python. Compared to Python, Hy offers a variety of new features, generalizations, and syntactic simplifications, as would be expected of a Lisp. Compared to other Lisps, Hy provides direct access to Python's built-ins and third-party Python libraries, while allowing you to freely mix imperative, functional, and object-oriented styles of programming. (More on "Why Hy?")

Some examples on the homepage:

Hy:

 hy

    
(defmacro do-while [test #* body]
  `(do
    ~@body
    (while ~test
      ~@body)))

(setv x 0)
(do-while x
  (print "Printed once."))

  

Python:

 python

    
x = 0
print("Printed once.")
while x:
    print("Printed once.")


  

Interestingly programming.dev's Mark

GitHub (source code for all languages), also linked above.

• Assembly
• BASIC
• Forth/MOUSE
• Lisp
• APL/K
• PL/0

The GitHub says "50 lines of code" but the largest example is 74 lines excluding whitespace and comments.

Dune is a shell designed for powerful scripting. Think of it as an unholy combination of bash and Lisp.

You can do all the normal shell operations like piping, file redirection, and running programs. But, you also have access to a standard library and functional programming abstractions for various programming and sysadmin tasks!

Fennel is a programming language that brings together the simplicity, speed, and reach of Lua with the flexibility of a lisp syntax and macro system.

• Full Lua compatibility: Easily call any Lua function or library from Fennel and vice-versa.
• Zero overhead: Compiled code should be just as efficient as hand-written Lua.
• Compile-time macros: Ship compiled code with no runtime dependency on Fennel.
• Embeddable: Fennel is a one-file library as well as an executable. Embed it in other programs to support runtime extensibility and interactive development.

Anywhere you can run Lua code, you can run Fennel code.

Example:

 lisp

    
;; Sample: read the state of the keyboard and move the player accordingly
(local dirs {:up [0 -1] :down [0 1] :left [-1 0] :right [1 0]})

(each [key [dx dy] (pairs dirs)]
  (when (love.keyboard.isDown key)
    (let [[px py]
  

Abstract:

 undefined

        We say that an imperative data structure is *snapshottable* or *supports snapshots* if we can efficiently capture its current state, and restore a previously captured state to become the current state again. This is useful, for example, to implement backtracking search processes that update the data structure during search.

    Inspired by a data structure proposed in 1978 by Baker, we present a *snapshottable store*, a bag of mutable references that supports snapshots. Instead of capturing and restoring an array, we can capture an arbitrary set of references (of any type) and restore all of them at once. This snapshottable store can be used as a building block to support snapshots for arbitrary data structures, by simply replacing all mutable references in the data structure by our store references. We present use-cases of a snapshottable store when implementing type-checkers and automated theorem provers.

    Our implementation is designed to provide a very low over