MAL in Crystal

Forked from https://github.com/kanaka/mal/tree/master/impls/crystal

Why Crystal?

My previous experiment was to build MAL in Pony. Pony is a nice language, but its type system is a bit "rigid", which slows down me. I want to experiment and iterate fast.

I want a compiled fast language, but not C. My options are:

• Go - I don't want to deal with the absence of generics
• Rust - I don't want to deal with the borrow checker
• Chez Scheme or sbcl or clasp - may be, but there is no static type checker?
• Zig
• Crystal

I decided to go with Crystal because it is a bit more flexible than Zig. Also, I heard that they want to rewrite the Ponylang compiler from C to Crystal, so I was curious.

Ideas

Ideas I want to explore:

1. Write reader with new Pytonish syntax, which would compile input to the SExpressions, that MAL's eval expect
2. ...

About Lisp syntax

There were a million attempts to create an alternative to SExpressions. See:

• History of alternative syntaxes for Lisp
• Readable Lisp S-expressions Project
• LISP Infix Syntax Survey
• wisp: Whitespace to Lisp
• Curly infix, Modern-expressions, and Sweet-expressions: A suite of readable formats for Lisp-like languages
• nonelang
• LSIP: An operator-based syntax for Racket programs; O-expressions
• rhombus-brainstorming

Parsers

Crystal libs

• http://crystalshards.xyz/?filter=parser
• arborist
  • ohm
• pars3k
• crystal-pegmatite - no documentation
• pegasus - regexp

Lisp, Sheme, Clojure BNF/EBNF

• Clojure.g4
• Clojure.g
• r5rs
• Formal Syntax of Scheme

Grammars

• The Packrat Parsing and Parsing Expression Grammars Page
• Language Grammar
• Confluent Orthogonal Drawingfor Syntax Diagrams
• Guy Steele on Computer Science Metanotation

Brainstorming

• operator precedence rules is hard to remeber. Pony doesn't have it
• punctuation-signs as operators are hard to search
• I don't think that prefix notation is a problem, almost all functions except math operators and special operators like in Haskell use it. See: operators
• In Scheme it is possible to use [] and {} in addition to (), which makes it more readable
• In Clojure [] denotes a vector (doesn't evaluate like application), {} denotes a hashmap, :... denotes a keyword (doesn't evaluate like a variable, more like Ruby's symbol)