μLithp - a Lisp in 27 lines of Ruby

aris · January 5, 2013, 1:17am

Hello,

Founded on Hacker new :
http://fogus.github.com/ulithp/

lisp eval code:

fogus/ulithp/blob/master/src/lithp.rb

class Lisp
  def initialize(ext={})
    @env = { :label => proc { |(name,val), _| @env[name] = eval(val, @env) },
             :car   => lambda { |(list), _| list[0] },
             :cdr   => lambda { |(list), _| list.drop 1 },
             :cons  => lambda { |(e,cell), _| [e] + cell },
             :eq    => lambda { |(l,r), ctx| eval(l, ctx) == eval(r, ctx) },
             :if    => proc { |(cond, thn, els), ctx| eval(cond, ctx) ? eval(thn, ctx) : eval(els, ctx) },
             :atom  => lambda { |(sexpr), _| (sexpr.is_a? Symbol) or (sexpr.is_a? Numeric) },
             :quote => proc { |sexpr, _| sexpr[0] } }.merge(ext)
  end

  def apply fn, args, ctx=@env
    return ctx[fn].call(args, ctx) if ctx[fn].respond_to? :call
    self.eval ctx[fn][2], ctx.merge(Hash[*(ctx[fn][1].zip args).flatten(1)])
  end

  def eval sexpr, ctx=@env
    return(ctx[sexpr] || sexpr) if ctx[:atom].call [sexpr], ctx
    fn, *args = sexpr

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scanner:

github.com

fogus/ulithp/blob/master/src/reader.rb

class Reader
  def initialize(expression)
    @tokens = expression.scan /[()]|\w+|".*?"|'.*?'/
  end

  def peek
    @tokens.first
  end

  def next_token
    @tokens.shift
  end

  def read
    return :"no more forms" if @tokens.empty?

    if (token = next_token) == '('
      read_list
    elsif token =~ /['"].*/
      token[1..-2]

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code example:

(label second (quote (lambda (l) (car (cdr l)))))
(label third (quote (lambda (l) (car (cdr (cdr l))))))

http://news.ycombinator.com/rss

raubarede · January 5, 2013, 6:41am

awesome.