crystal/stepA_mal.cr

   1 #! /usr/bin/env crystal run
   2
   3 require "colorize"
   4
   5 require "./readline"
   6 require "./reader"
   7 require "./printer"
   8 require "./types"
   9 require "./env"
  10 require "./core"
  11 require "./error"
  12
  13 # Note:
  14 # Employed downcase names because Crystal prohibits uppercase names for methods
  15
  16 module Mal
  17   extend self
  18
  19   def func_of(env, binds, body)
  20     -> (args : Array(Mal::Type)) {
  21       new_env = Mal::Env.new(env, binds, args)
  22       eval(body, new_env)
  23     } as Mal::Func
  24   end
  25
  26   def eval_ast(ast, env)
  27     return ast.map{|n| eval(n, env) as Mal::Type} if ast.is_a? Array
  28
  29     val = ast.unwrap
  30
  31     Mal::Type.new case val
  32     when Mal::Symbol
  33       if e = env.get(val.str)
  34         e
  35       else
  36         eval_error "'#{val.str}' not found"
  37       end
  38     when Mal::List
  39       val.each_with_object(Mal::List.new){|n, l| l << eval(n, env)}
  40     when Mal::Vector
  41       val.each_with_object(Mal::Vector.new){|n, l| l << eval(n, env)}
  42     when Mal::HashMap
  43       new_map = Mal::HashMap.new
  44       val.each{|k, v| new_map[k] = eval(v, env)}
  45       new_map
  46     else
  47       val
  48     end
  49   end
  50
  51   def read(str)
  52     read_str str
  53   end
  54
  55   macro pair?(list)
  56     {{list}}.is_a?(Array) && !{{list}}.empty?
  57   end
  58
  59   def quasiquote(ast)
  60     list = ast.unwrap
  61
  62     unless pair?(list)
  63       return Mal::Type.new(
  64         Mal::List.new << gen_type(Mal::Symbol, "quote") << ast
  65       )
  66     end
  67
  68     head = list.first.unwrap
  69
  70     case
  71     # ("unquote" ...)
  72     when head.is_a?(Mal::Symbol) && head.str == "unquote"
  73       list[1]
  74     # (("splice-unquote" ...) ...)
  75     when pair?(head) && (arg0 = head.first.unwrap).is_a?(Mal::Symbol) && arg0.str == "splice-unquote"
  76       tail = Mal::Type.new list[1..-1].to_mal
  77       Mal::Type.new(
  78         Mal::List.new << gen_type(Mal::Symbol, "concat") << head[1] << quasiquote(tail)
  79       )
  80     else
  81       tail = Mal::Type.new list[1..-1].to_mal
  82       Mal::Type.new(
  83         Mal::List.new << gen_type(Mal::Symbol, "cons") << quasiquote(list.first) << quasiquote(tail)
  84       )
  85     end
  86   end
  87
  88   def macro_call?(ast, env)
  89     list = ast.unwrap
  90     return false unless list.is_a? Mal::List
  91     return false if list.empty?
  92
  93     sym = list.first.unwrap
  94     return false unless sym.is_a? Mal::Symbol
  95
  96     func = env.find(sym.str).try(&.data[sym.str])
  97     return false unless func && func.macro?
  98
  99     true
 100   end
 101
 102   def macroexpand(ast, env)
 103     while macro_call?(ast, env)
 104
 105       # Already checked in macro_call?
 106       list = ast.unwrap as Mal::List
 107       func_sym = list[0].unwrap as Mal::Symbol
 108       func = env.get(func_sym.str).unwrap
 109
 110       case func
 111       when Mal::Func
 112         ast = func.call(list[1..-1])
 113       when Mal::Closure
 114         ast = func.fn.call(list[1..-1])
 115       else
 116         eval_error "macro '#{func_sym.str}' must be function: #{ast}"
 117       end
 118     end
 119
 120     ast
 121   end
 122
 123   macro invoke_list(l, env)
 124     f = eval({{l}}.first, {{env}}).unwrap
 125     args = eval_ast({{l}}[1..-1], {{env}}) as Array
 126
 127     case f
 128     when Mal::Closure
 129       ast = f.ast
 130       {{env}} = Mal::Env.new(f.env, f.params, args)
 131       next # TCO
 132     when Mal::Func
 133       return f.call args
 134     else
 135       eval_error "expected function as the first argument: #{f}"
 136     end
 137   end
 138
 139   def debug(ast)
 140     puts print(ast).colorize.red
 141   end
 142
 143   def eval(ast, env)
 144     # 'next' in 'do...end' has a bug in crystal 0.7.1
 145     # https://github.com/manastech/crystal/issues/659
 146     while true
 147       return eval_ast(ast, env) unless ast.unwrap.is_a? Mal::List
 148
 149       ast = macroexpand(ast, env)
 150
 151       list = ast.unwrap
 152
 153       return eval_ast(ast, env) unless list.is_a? Mal::List
 154       return ast if list.empty?
 155
 156       head = list.first.unwrap
 157
 158       return invoke_list(list, env) unless head.is_a? Mal::Symbol
 159
 160       return Mal::Type.new case head.str
 161         when "def!"
 162           eval_error "wrong number of argument for 'def!'" unless list.size == 3
 163           a1 = list[1].unwrap
 164           eval_error "1st argument of 'def!' must be symbol: #{a1}" unless a1.is_a? Mal::Symbol
 165           env.set(a1.str, eval(list[2], env))
 166         when "let*"
 167           eval_error "wrong number of argument for 'def!'" unless list.size == 3
 168
 169           bindings = list[1].unwrap
 170           eval_error "1st argument of 'let*' must be list or vector" unless bindings.is_a? Array
 171           eval_error "size of binding list must be even" unless bindings.size.even?
 172
 173           new_env = Mal::Env.new env
 174           bindings.each_slice(2) do |binding|
 175             key, value = binding
 176             name = key.unwrap
 177             eval_error "name of binding must be specified as symbol #{name}" unless name.is_a? Mal::Symbol
 178             new_env.set(name.str, eval(value, new_env))
 179           end
 180
 181           ast, env = list[2], new_env
 182           next # TCO
 183         when "do"
 184           if list.empty?
 185             ast = Mal::Type.new nil
 186             next
 187           end
 188
 189           eval_ast(list[1..-2].to_mal, env)
 190           ast = list.last
 191           next # TCO
 192         when "if"
 193           ast = unless eval(list[1], env).unwrap
 194             list.size >= 4 ? list[3] : Mal::Type.new(nil)
 195           else
 196             list[2]
 197           end
 198           next # TCO
 199         when "fn*"
 200           params = list[1].unwrap
 201           unless params.is_a? Array
 202             eval_error "'fn*' parameters must be list or vector: #{params}"
 203           end
 204           Mal::Closure.new(list[2], params, env, func_of(env, params, list[2]))
 205         when "quote"
 206           list[1]
 207         when "quasiquote"
 208           ast = quasiquote list[1]
 209           next # TCO
 210         when "defmacro!"
 211           eval_error "wrong number of argument for 'defmacro!'" unless list.size == 3
 212           a1 = list[1].unwrap
 213           eval_error "1st argument of 'defmacro!' must be symbol: #{a1}" unless a1.is_a? Mal::Symbol
 214           env.set(a1.str, eval(list[2], env).tap{|n| n.is_macro = true})
 215         when "macroexpand"
 216           macroexpand(list[1], env)
 217         when "try*"
 218           catch_list = list[2].unwrap
 219           return eval(list[1], env) unless catch_list.is_a? Mal::List
 220
 221           catch_head = catch_list.first.unwrap
 222           return eval(list[1], env) unless catch_head.is_a? Mal::Symbol
 223           return eval(list[1], env) unless catch_head.str == "catch*"
 224
 225           begin
 226             eval(list[1], env)
 227           rescue e : Mal::RuntimeException
 228             new_env = Mal::Env.new(env, [catch_list[1]], [e.thrown])
 229             eval(catch_list[2], new_env)
 230           rescue e
 231             new_env = Mal::Env.new(env, [catch_list[1]], [Mal::Type.new e.message])
 232             eval(catch_list[2], new_env)
 233           end
 234         else
 235           invoke_list(list, env)
 236         end
 237     end
 238   end
 239
 240   def print(result)
 241     pr_str(result, true)
 242   end
 243
 244   def rep(str)
 245     print(eval(read(str), $repl_env))
 246   end
 247 end
 248
 249 $repl_env = Mal::Env.new nil
 250 Mal::NS.each{|k,v| $repl_env.set(k, Mal::Type.new(v))}
 251 $repl_env.set("eval", Mal::Type.new -> (args: Array(Mal::Type)){ Mal.eval(args[0], $repl_env) })
 252 Mal.rep "(def! not (fn* (a) (if a false true)))"
 253 Mal.rep "(def! load-file (fn* (f) (eval (read-string (str \"(do \" (slurp f) \")\")))))"
 254 Mal.rep "(defmacro! cond (fn* (& xs) (if (> (count xs) 0) (list 'if (first xs) (if (> (count xs) 1) (nth xs 1) (throw \"odd number of forms to cond\")) (cons 'cond (rest (rest xs)))))))"
 255 Mal.rep "(def! *gensym-counter* (atom 0))"
 256 Mal.rep "(def! gensym (fn* [] (symbol (str \"G__\" (swap! *gensym-counter* (fn* [x] (+ 1 x)))))))"
 257 Mal.rep "(defmacro! or (fn* (& xs) (if (empty? xs) nil (if (= 1 (count xs)) (first xs) (let* (condvar (gensym)) `(let* (~condvar ~(first xs)) (if ~condvar ~condvar (or ~@(rest xs)))))))))"
 258 Mal.rep("(def! *host-language* \"crystal\")")
 259
 260 $argv = Mal::List.new
 261 $repl_env.set("*ARGV*", Mal::Type.new $argv)
 262
 263 unless ARGV.empty?
 264   if ARGV.size > 1
 265     ARGV[1..-1].each do |a|
 266       $argv << Mal::Type.new(a)
 267     end
 268   end
 269
 270   begin
 271     Mal.rep "(load-file \"#{ARGV[0]}\")"
 272   rescue e
 273     STDERR.puts e
 274   end
 275   exit
 276 end
 277
 278 Mal.rep("(println (str \"Mal [\" *host-language* \"]\"))")
 279
 280 while line = my_readline("user> ")
 281   begin
 282     puts Mal.rep(line)
 283   rescue e
 284     STDERR.puts e
 285   end
 286 end