crystal/step7_quote.cr

   1 #! /usr/bin/env crystal run
   2
   3 require "readline"
   4 require "./reader"
   5 require "./printer"
   6 require "./types"
   7 require "./env"
   8 require "./core"
   9 require "./error"
  10
  11 # Note:
  12 # Employed downcase names because Crystal prohibits uppercase names for methods
  13
  14 module Mal
  15   extend self
  16
  17   def func_of(env, binds, body)
  18     ->(args : Array(Mal::Type)) {
  19       new_env = Mal::Env.new(env, binds, args)
  20       eval(body, new_env)
  21     }.as(Mal::Func)
  22   end
  23
  24   def eval_ast(ast, env)
  25     return ast.map { |n| eval(n, env).as(Mal::Type) } if ast.is_a? Mal::List
  26
  27     val = ast.unwrap
  28
  29     Mal::Type.new case val
  30     when Mal::Symbol
  31       if e = env.get(val.str)
  32         e
  33       else
  34         eval_error "'#{val.str}' not found"
  35       end
  36     when Mal::List
  37       val.each_with_object(Mal::List.new) { |n, l| l << eval(n, env) }
  38     when Mal::Vector
  39       val.each_with_object(Mal::Vector.new) { |n, l| l << eval(n, env) }
  40     when Array(Mal::Type)
  41       val.map { |n| eval(n, env).as(Mal::Type) }
  42     when Mal::HashMap
  43       val.each { |k, v| val[k] = eval(v, env) }
  44       val
  45     else
  46       val
  47     end
  48   end
  49
  50   def read(str)
  51     read_str str
  52   end
  53
  54   macro is_pair(list)
  55     {{list}}.is_a?(Array) && !{{list}}.empty?
  56   end
  57
  58   def quasiquote(ast)
  59     list = ast.unwrap
  60
  61     unless is_pair(list)
  62       return Mal::Type.new(
  63         Mal::List.new << gen_type(Mal::Symbol, "quote") << ast
  64       )
  65     end
  66
  67     head = list.first.unwrap
  68
  69     case
  70     # ("unquote" ...)
  71     when head.is_a?(Mal::Symbol) && head.str == "unquote"
  72       list[1]
  73       # (("splice-unquote" ...) ...)
  74     when is_pair(head) && (arg0 = head.first.unwrap).is_a?(Mal::Symbol) && arg0.str == "splice-unquote"
  75       tail = Mal::Type.new list[1..-1].each_with_object(Mal::List.new) { |e, l| l << e }
  76       Mal::Type.new(
  77         Mal::List.new << gen_type(Mal::Symbol, "concat") << head[1] << quasiquote(tail)
  78       )
  79     else
  80       tail = Mal::Type.new list[1..-1].each_with_object(Mal::List.new) { |e, l| l << e }
  81       Mal::Type.new(
  82         Mal::List.new << gen_type(Mal::Symbol, "cons") << quasiquote(list.first) << quasiquote(tail)
  83       )
  84     end
  85   end
  86
  87   macro invoke_list(l, env)
  88     f = eval({{l}}.first, {{env}}).unwrap
  89     args = eval_ast({{l}}[1..-1].each_with_object(Mal::List.new){|i, l| l << i}, {{env}})
  90     case f
  91     when Mal::Closure
  92       ast = f.ast
  93       {{env}} = Mal::Env.new(f.env, f.params, args)
  94       next # TCO
  95     when Mal::Func
  96       return f.call args
  97     else
  98       eval_error "expected function as the first argument"
  99     end
 100   end
 101
 102   def eval(ast, env)
 103     # 'next' in 'do...end' has a bug in crystal 0.7.1
 104     # https://github.com/manastech/crystal/issues/659
 105     while true
 106       list = ast.unwrap
 107
 108       return eval_ast(ast, env) unless list.is_a? Mal::List
 109       return gen_type Mal::List if list.empty?
 110
 111       head = list.first.unwrap
 112
 113       unless head.is_a? Mal::Symbol
 114         return invoke_list(list, env)
 115       end
 116
 117       return Mal::Type.new case head.str
 118       when "def!"
 119         eval_error "wrong number of argument for 'def!'" unless list.size == 3
 120         a1 = list[1].unwrap
 121         eval_error "1st argument of 'def!' must be symbol" unless a1.is_a? Mal::Symbol
 122         env.set(a1.str, eval(list[2], env))
 123       when "let*"
 124         eval_error "wrong number of argument for 'def!'" unless list.size == 3
 125
 126         bindings = list[1].unwrap
 127         eval_error "1st argument of 'let*' must be list or vector" unless bindings.is_a? Array
 128         eval_error "size of binding list must be even" unless bindings.size.even?
 129
 130         new_env = Mal::Env.new env
 131         bindings.each_slice(2) do |binding|
 132           key, value = binding
 133           name = key.unwrap
 134           eval_error "name of binding must be specified as symbol" unless name.is_a? Mal::Symbol
 135           new_env.set(name.str, eval(value, new_env))
 136         end
 137
 138         ast, env = list[2], new_env
 139         next # TCO
 140       when "do"
 141         if list.empty?
 142           ast = Mal::Type.new nil
 143           next
 144         end
 145
 146         eval_ast(list[1..-2].each_with_object(Mal::List.new) { |i, l| l << i }, env)
 147         ast = list.last
 148         next # TCO
 149       when "if"
 150         ast = unless eval(list[1], env).unwrap
 151           list.size >= 4 ? list[3] : Mal::Type.new(nil)
 152         else
 153           list[2]
 154         end
 155         next # TCO
 156       when "fn*"
 157         params = list[1].unwrap
 158         unless params.is_a? Array
 159           eval_error "'fn*' parameters must be list"
 160         end
 161         Mal::Closure.new(list[2], params, env, func_of(env, params, list[2]))
 162       when "quote"
 163         list[1]
 164       when "quasiquote"
 165         ast = quasiquote list[1]
 166         next # TCO
 167       else
 168         invoke_list(list, env)
 169       end
 170     end
 171   end
 172
 173   def print(result)
 174     pr_str(result, true)
 175   end
 176
 177   def rep(str)
 178     print(eval(read(str), REPL_ENV))
 179   end
 180 end
 181
 182 REPL_ENV = Mal::Env.new nil
 183 Mal::NS.each { |k, v| REPL_ENV.set(k, Mal::Type.new(v)) }
 184 REPL_ENV.set("eval", Mal::Type.new ->(args : Array(Mal::Type)) { Mal.eval(args[0], REPL_ENV) })
 185 Mal.rep "(def! not (fn* (a) (if a false true)))"
 186 Mal.rep "(def! load-file (fn* (f) (eval (read-string (str \"(do \" (slurp f) \")\")))))"
 187 argv = Mal::List.new
 188 REPL_ENV.set("*ARGV*", Mal::Type.new argv)
 189
 190 unless ARGV.empty?
 191   if ARGV.size > 1
 192     ARGV[1..-1].each do |a|
 193       argv << Mal::Type.new(a)
 194     end
 195   end
 196
 197   begin
 198     Mal.rep "(load-file \"#{ARGV[0]}\")"
 199   rescue e
 200     STDERR.puts e
 201   end
 202   exit
 203 end
 204
 205 while line = Readline.readline("user> ", true)
 206   begin
 207     puts Mal.rep(line)
 208   rescue e : Mal::RuntimeException
 209     STDERR.puts "Error: #{pr_str(e.thrown, true)}"
 210   rescue e
 211     STDERR.puts "Error: #{e}"
 212   end
 213 end