ruby/step3_env.rb

   1 require_relative "mal_readline"
   2 require_relative "types"
   3 require_relative "reader"
   4 require_relative "printer"
   5 require_relative "env"
   6
   7 # read
   8 def READ(str)
   9     return read_str(str)
  10 end
  11
  12 # eval
  13 def eval_ast(ast, env)
  14     return case ast
  15         when Symbol
  16             env.get(ast)
  17         when List
  18             List.new ast.map{|a| EVAL(a, env)}
  19         when Vector
  20             Vector.new ast.map{|a| EVAL(a, env)}
  21         when Hash
  22             new_hm = {}
  23             ast.each{|k,v| new_hm[EVAL(k,env)] = EVAL(v, env)}
  24             new_hm
  25         else
  26             ast
  27     end
  28 end
  29
  30 def EVAL(ast, env)
  31     #puts "EVAL: #{_pr_str(ast, true)}"
  32
  33     if not ast.is_a? List
  34         return eval_ast(ast, env)
  35     end
  36     if ast.empty?
  37         return ast
  38     end
  39
  40     # apply list
  41     a0,a1,a2,a3 = ast
  42     case a0
  43     when :def!
  44         return env.set(a1, EVAL(a2, env))
  45     when :"let*"
  46         let_env = Env.new(env)
  47         a1.each_slice(2) do |a,e|
  48             let_env.set(a, EVAL(e, let_env))
  49         end
  50         return EVAL(a2, let_env)
  51     else
  52         el = eval_ast(ast, env)
  53         f = el[0]
  54         return f[*el.drop(1)]
  55     end
  56 end
  57
  58 # print
  59 def PRINT(exp)
  60     return _pr_str(exp, true)
  61 end
  62
  63 # repl
  64 repl_env = Env.new
  65 REP = lambda {|str| PRINT(EVAL(READ(str), repl_env)) }
  66
  67 repl_env.set(:+, lambda {|a,b| a + b})
  68 repl_env.set(:-, lambda {|a,b| a - b})
  69 repl_env.set(:*, lambda {|a,b| a * b})
  70 repl_env.set(:/, lambda {|a,b| a / b})
  71
  72 # repl loop
  73 while line = _readline("user> ")
  74     begin
  75         puts REP[line]
  76     rescue Exception => e
  77         puts "Error: #{e}"
  78         puts "\t#{e.backtrace.join("\n\t")}"
  79     end
  80 end