Show HN: A physically-based GPU ray tracer written in Julia

super cool!

This was supposed to be under a different post. Not the main article. Whops.

First, let's distinguish between two types of syntactic constructs: null and left denominations. (Terminology borrowed from Pratt parsers.) Null denominations can exist on their own, left denominations can't -- they are inherently chained (eg arithmetic expressions, statements in a block, or elements of a tuple), and allow a succinct, infix notation for variable-length constructs (no lispy parentheses hell).

Second, null denominations usually introduce names -- whether for variables, types, functions, lifetimes, macros, etc. One exception to this are free-standing value expressions (a bit weird; less so when they're the last expression in a block indicating the value returned by it). Another other exception would be directive type constructs - eg directives to import names from another module, directives to give hints to the compiler, etc. The last two exceptions are the most common ones: variable assignment and function invocation.

The golden rule of good language design, as I see it, is this: null denominations must begin with a fixed and unique token. The only permissible exceptions should be for assignment and function invocation; exceptions which exist because those use-cases appear so often in a typical program that requiring a prefix would be insufferable.

Julia breaks this rule for global variables. (Fair enough, Python also commits this error, but it's a mistake and a source of bugs!) But wait, Julia also has "const" and "local" binding constructs, where it follows the golden rule -- but now your syntax isn't consistent. So now you need to keep in your head these nuances -- and know the difference between a soft and hard scope -- when you want to write a function which modifies a function using macrology.

(As a point of taste on the choice of prefix token: introduction of variables through "local" is just as weird as C++'s "auto" -- and at least Bjarne Stroustroup had an excuse for that choice. Anyone who introduces a global variable in a local scope should be punished imho, so there's no need to say "this is a local variable", it's obvious from the fact that the name is introduced inside a function. Instead, my personal preference is to introduce constants through "let", and variables through "var". The former is well-known to anyone numerate, and the latter is ubiquitous in software engineering. Both read well; they're as close as possible as you can get to constructs in English.)

Julia breaks the golden rule again with its succinct, Mathematica-style notation for function definition. I get that it wants to appeal to Mathematica users, but Python already proved you don't need to do that. This is a programming language; brainy types, like mathematicians and physicists, aren't going to be flummoxed by an unfamiliar notation for function definition, or irritated by having to type a few extra characters.

I mention macrology; it's not just that. Let's say you want write a syntax highlighter -- you need to take into account all that weirdness. If null denominations have a fixed & unique prefix, parsing is easy-peasy. Want to add a capability to "inline" HTML code within Julia, react-style? You're going to run into similar issues. And so on...

... Actually, this only worked for Linux. My Windows container is back to precompiling every time, again, and Windows was the slow one that I wanted to fix in the first place. I had to revert this. Back to the drawing board. I wish Julia would print some diagnostics about why it decided to precompile again.