Comp Language Syntax

An ongoing series in my quest to untangle my own thoughts and goals for the Comp programming language.

A language focused on developer experience? So much of my focus has been on the syntax and grammar. The entire concept is built on a handful of core fundamental rules that everything expands from.

• No separators or terminators
• Whitespace independent
  • No line-based statements
  • No indentation

Along with these fundamentals there are a few other strongly motivated designs.

• Use kabab-case for identifiers
• No keywords
• Avoid nesting braces

Along with that there is has been from-the-start requirement that the structure literal has two forms.

• {1 2 3} for positional sequences (lists, arrays)
• {a=1 b=2} for named mappings (dicts, hashes)

This has been a long and ongoing puzzle, but the payoff has been spectacular. Let's look at another small code example and call out a few highlights.

!func shopping-cart-demo (
  {
    {"Apple" price=1.00}
    {"Banana" price=0.50 quantity=2}
    {"Apple" 1.00 quantity=2}  // replace previous apples
  }
  | reduce :(| upsert :($.name))
  | cart-total
  | output "Total: %()"
)

• Keywords use a ! prefix. This makes them a bit noisier than I'd like, but it's not a bad design to make them pronounced. This also allows freely introducing new keywords in the future.
• Whitespace independence means this entire definition could be placed on a single line, or each statement split or joined as the author decides is most readable.

There's a history of experiments, compromises, and undesirable workarounds to assemble these pieces. Much of this time I wasn't sure these constraints could even be appeased.

I've been using the Lark library to handle parsing. I'd never experimented with it before, but now have a good deal of experience stretching it's LALR rules. This gives an ideal O(n) performance. I have been surprised at the cost of building the grammar at runtime. Fortunately the library is quite prepared for this and comes with some high level caching options.