Class: Risp::Interpreter

Inherits:
Object
  • Object
show all
Defined in:
lib/risp/interpreter.rb

Constant Summary collapse

SPECIAL_FORMS = 
{
  def: -> (elems, binding, locals, macros) {
    symbol, value = elems
    binding[symbol.name] = eval(value, binding, locals, macros)
  },
  let: -> (elems, binding, locals, macros) {
    (*assigns), *forms = elems
    locals = assigns.each_slice(2).reduce(locals.dup) do |locals, (s, v)|
      locals.merge assign_args([s], [eval(v, binding, locals, macros)])
    end
    forms.map { |form| eval(form, binding, locals, macros) }.last
  },
  fn: -> (elems, binding, locals, macros) {
    (*as), body = elems
    -> (*args) do
      locals = locals.merge(assign_args(as, args))
      eval(body, binding, locals, macros)
    end
  },
  do: -> (elems, binding, locals, macros) {
    elems.map { |el| eval(el, binding, locals, macros) }.last
  },
  if: -> (elems, binding, locals, macros) {
    condition, _then, _else = elems
    if eval(condition, binding, locals, macros)
      eval(_then, binding, locals, macros)
    else
      eval(_else, binding, locals, macros)
    end
  },
  quote: -> (elems, binding, locals, macros) {
    unquote(elems.first, binding, locals, macros)
  },
  defmacro: -> (elems, binding, locals, macros) {
    symbol, (*as), body = elems
    macros[symbol.name] = -> (*args) do
      locals = locals.merge(assign_args(as, args))
      eval(body, binding, locals, macros)
    end
  },
  apply: -> (elems, binding, locals, macros) {
    fn, args = elems.map { |x| eval(x, binding, locals, macros) }
    fn.call(*args)
  },
  require: -> (elems, binding, locals, macros) {
    elems.each do |lib|
      require lib
    end
  }
}

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ Interpreter

Returns a new instance of Interpreter.



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# File 'lib/risp/interpreter.rb', line 60

def initialize()
  @binding = {}
  @macros  = {}
  @lexer   = Risp::Lexer.new
  @parser  = Risp::Parser.new
  corelib  = File.read(File.expand_path('core.risp', File.dirname(__FILE__)))
  eval(corelib)
end

Instance Attribute Details

#binding ⇒ Object (readonly)

Returns the value of attribute binding.



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# File 'lib/risp/interpreter.rb', line 7

def binding
  @binding
end

#lexer ⇒ Object (readonly)

Returns the value of attribute lexer.



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# File 'lib/risp/interpreter.rb', line 7

def lexer
  @lexer
end

#macros ⇒ Object (readonly)

Returns the value of attribute macros.



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# File 'lib/risp/interpreter.rb', line 7

def macros
  @macros
end

#parser ⇒ Object (readonly)

Returns the value of attribute parser.



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# File 'lib/risp/interpreter.rb', line 7

def parser
  @parser
end

Class Method Details

.assign_args(symbols, values) ⇒ Object 



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# File 'lib/risp/interpreter.rb', line 133

def self.assign_args(symbols, values)
  symbols.each_with_index.reduce({}) do |a, (s, i)|
    v = values[i]
    if s.is_a?(Hamster::Vector) && v.is_a?(Enumerable)
      a.merge(assign_args(s, v))
    elsif s.is_a?(Risp::Splat)
      a[s.name] = values.drop(i)
      a
    else
      a[s.name] = v
      a
    end
  end
end

.eval(expr, binding, locals, macros) ⇒ Object 



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# File 'lib/risp/interpreter.rb', line 73

def self.eval(expr, binding, locals, macros)
  case expr
  when Hamster::List
    first = expr.first
    if special = first.is_a?(Risp::Symbol) && SPECIAL_FORMS[first.name]
      special.call(expr.drop(1), binding, locals, macros)
    elsif macro = first.is_a?(Risp::Symbol) && macros[first.name]
      _, *args = expr
      eval(macro.call(*args), binding, locals, macros)
    elsif first.is_a?(Risp::Method)
      receiver, *args = expr.drop(1).map { |x| eval(x, binding, locals, macros) }
      if args.last.is_a?(Proc) && receiver.method(first.name).arity < args.size
        *args, block = args
        receiver.send(first.name, *args, &block)
      else
        receiver.send(first.name, *args)
      end
    else
      fn, *args = expr.map { |x| eval(x, binding, locals, macros) }
      fn.call(*args)
    end
  when Risp::Symbol
    symbol = expr.name
    resolve(symbol, binding, locals, macros)
  when Enumerable
    expr.map { |x| eval(x, binding, locals, macros) }
  else
    expr
  end
end

.resolve(symbol, binding, locals, macros) ⇒ Object 



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# File 'lib/risp/interpreter.rb', line 117

def self.resolve(symbol, binding, locals, macros)
  if locals.has_key?(symbol)
    locals[symbol]
  elsif binding.has_key?(symbol)
    binding[symbol]
  else
    begin
      symbol.to_s.split('/').reduce(Object) do |c, p|
        c.const_get(p)
      end
    rescue NameError => e
      raise "cannot resolve #{symbol}"
    end
  end
end

.unquote(expr, binding, locals, macros) ⇒ Object 



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# File 'lib/risp/interpreter.rb', line 104

def self.unquote(expr, binding, locals, macros)
  if expr.is_a?(Enumerable) && !expr.is_a?(Risp::Symbol)
    first, second = expr
    if first.is_a?(Risp::Symbol) && first.name == :unquote
      eval(second, binding, locals, macros)
    else
      expr.map { |x| unquote(x, binding, locals, macros) }
    end
  else
    expr
  end
end

Instance Method Details

#eval(code) ⇒ Object 



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# File 'lib/risp/interpreter.rb', line 69

def eval(code)
  parser.parse(lexer.lex(code)).map { |x| self.class.eval(x, binding, {}, macros) }.last
end