crystal/step3_env.cr

   1 #! /usr/bin/env crystal run
   2
   3 require "readline"
   4 require "./reader"
   5 require "./printer"
   6 require "./types"
   7 require "./env"
   8
   9 # Note:
  10 # Employed downcase names because Crystal prohibits uppercase names for methods
  11
  12 def eval_error(msg)
  13   raise Mal::EvalException.new msg
  14 end
  15
  16 def num_func(func)
  17   ->(args : Array(Mal::Type)) {
  18     x, y = args[0].unwrap, args[1].unwrap
  19     eval_error "invalid arguments" unless x.is_a?(Int64) && y.is_a?(Int64)
  20     Mal::Type.new func.call(x, y)
  21   }
  22 end
  23
  24 REPL_ENV = Mal::Env.new nil
  25 REPL_ENV.set("+", Mal::Type.new num_func(->(x : Int64, y : Int64) { x + y }))
  26 REPL_ENV.set("-", Mal::Type.new num_func(->(x : Int64, y : Int64) { x - y }))
  27 REPL_ENV.set("*", Mal::Type.new num_func(->(x : Int64, y : Int64) { x * y }))
  28 REPL_ENV.set("/", Mal::Type.new num_func(->(x : Int64, y : Int64) { x / y }))
  29
  30 module Mal
  31   extend self
  32
  33   def eval_ast(a, env)
  34     return a.map { |n| eval(n, env) } if a.is_a? Array
  35
  36     Mal::Type.new case ast = a.unwrap
  37     when Mal::Symbol
  38       if e = env.get(ast.str)
  39         e
  40       else
  41         eval_error "'#{ast.str}' not found"
  42       end
  43     when Mal::List
  44       ast.each_with_object(Mal::List.new) { |n, l| l << eval(n, env) }
  45     when Mal::Vector
  46       ast.each_with_object(Mal::Vector.new) { |n, l| l << eval(n, env) }
  47     when Mal::HashMap
  48       new_map = Mal::HashMap.new
  49       ast.each { |k, v| new_map[k] = eval(v, env) }
  50       new_map
  51     else
  52       ast
  53     end
  54   end
  55
  56   def read(str)
  57     read_str str
  58   end
  59
  60   def eval(t, env)
  61     ast = t.unwrap
  62
  63     return eval_ast(t, env) unless ast.is_a?(Mal::List)
  64     return gen_type Mal::List if ast.empty?
  65
  66     sym = ast.first.unwrap
  67     eval_error "first element of list must be a symbol" unless sym.is_a?(Mal::Symbol)
  68
  69     Mal::Type.new case sym.str
  70     when "def!"
  71       eval_error "wrong number of argument for 'def!'" unless ast.size == 3
  72       a1 = ast[1].unwrap
  73       eval_error "1st argument of 'def!' must be symbol" unless a1.is_a?(Mal::Symbol)
  74       env.set(a1.str, eval(ast[2], env).as(Mal::Type))
  75     when "let*"
  76       eval_error "wrong number of argument for 'def!'" unless ast.size == 3
  77
  78       bindings = ast[1].unwrap
  79       eval_error "1st argument of 'let*' must be list or vector" unless bindings.is_a?(Array)
  80       eval_error "size of binding list must be even" unless bindings.size.even?
  81
  82       new_env = Mal::Env.new env
  83       bindings.each_slice(2) do |binding|
  84         name, value = binding[0].unwrap, binding[1]
  85         eval_error "name of binding must be specified as symbol" unless name.is_a?(Mal::Symbol)
  86         new_env.set(name.str, eval(value, new_env))
  87       end
  88
  89       eval(ast[2], new_env)
  90     else
  91       f = eval_ast(ast.first, env)
  92       ast.shift(1)
  93       args = eval_ast(ast, env)
  94
  95       if f.is_a?(Mal::Type) && (f2 = f.unwrap).is_a?(Mal::Func)
  96         f2.call(args.as(Array(Mal::Type)))
  97       else
  98         eval_error "expected function symbol as the first symbol of list"
  99       end
 100     end
 101   end
 102
 103   def print(result)
 104     pr_str(result, true)
 105   end
 106
 107   def rep(str)
 108     print(eval(read(str), REPL_ENV))
 109   end
 110 end
 111
 112 while line = Readline.readline("user> ", true)
 113   begin
 114     puts Mal.rep(line)
 115   rescue e : Mal::RuntimeException
 116     STDERR.puts "Error: #{pr_str(e.thrown, true)}"
 117   rescue e
 118     STDERR.puts "Error: #{e}"
 119   end
 120 end