Heist 0.2.0, now with full list support

Hi all,

I just released the 0.2.0 version of Heist, my Ruby Scheme runtime.
in this release include:

  • Entirely revised to correctly support lists as linked pairs
  • Complete set of R5RS list functions
  • Syntax for dotted pairs and improper lists implemented
  • Rest-args for functions using dot notation
  • Almost-complete R5RS numeric library, including complexes and
  • Some parser bugs regarding literals and quoting fixed
  • Many macro parsing and expansion bugs fixed, esp. concerning nested
    repeating patterns
  • Macro keywords and collisions with local variables now follow the spec
  • R6RS ellipsis escaping feature – (… …) – implemented
  • All library syntax now implemented as macros, should all support
  • Ruby data can now be executed as Scheme code
  • Lots of inline documentation for the runtime

More information on GitHub and my blog:


Of particular interest to me is the Ruby-data-as-Scheme-code feature,

scheme = Heist::Runtime.new

scheme.exec [:define, [:square, :x],
[:*, :x, :x]]

scheme.exec [:square, 9]
#=> 81

Once I’ve settled on a nice way to expose the macro system to Ruby, this
could be used with ParseTree to rewrite Ruby code, like raganwald’s
‘rewrite’ gem. Also, there’s a possibility for someone to write a new
interpreter by taking ParseTree and adding a new set of built-in
to the Heist runtime to execute its output. If someone has a serious
stab at
this I’d love to see the results.