julia/step5_tco.jl

   1 #!/usr/bin/env julia
   2
   3 push!(LOAD_PATH, pwd(), "/usr/share/julia/base")
   4 import readline_mod
   5 import reader
   6 import printer
   7 using env
   8 import core
   9 using types
  10
  11 # READ
  12 function READ(str)
  13     reader.read_str(str)
  14 end
  15
  16 # EVAL
  17 function eval_ast(ast, env)
  18     if typeof(ast) == Symbol
  19         env_get(env,ast)
  20     elseif isa(ast, Array) || isa(ast, Tuple)
  21         map((x) -> EVAL(x,env), ast)
  22     elseif isa(ast, Dict)
  23         [EVAL(x[1],env) => EVAL(x[2], env) for x=ast]
  24     else
  25         ast
  26     end
  27 end
  28
  29 function EVAL(ast, env)
  30   while true
  31     #println("EVAL: $(printer.pr_str(ast,true))")
  32     if !isa(ast, Array) return eval_ast(ast, env) end
  33
  34     # apply
  35     if     :def! == ast[1]
  36         return env_set(env, ast[2], EVAL(ast[3], env))
  37     elseif symbol("let*") == ast[1]
  38         let_env = Env(env)
  39         for i = 1:2:length(ast[2])
  40             env_set(let_env, ast[2][i], EVAL(ast[2][i+1], let_env))
  41         end
  42         env = let_env
  43         ast = ast[3]
  44         # TCO loop
  45     elseif :do == ast[1]
  46         eval_ast(ast[2:end-1], env)
  47         ast = ast[end]
  48         # TCO loop
  49     elseif :if == ast[1]
  50         cond = EVAL(ast[2], env)
  51         if cond === nothing || cond === false
  52             if length(ast) >= 4
  53                 ast = ast[4]
  54                 # TCO loop
  55             else
  56                 return nothing
  57             end
  58         else
  59             ast = ast[3]
  60             # TCO loop
  61         end
  62     elseif symbol("fn*") == ast[1]
  63         return MalFunc(
  64             (args...) -> EVAL(ast[3], Env(env, ast[2], args)),
  65             ast[3], env, ast[2])
  66     else
  67         el = eval_ast(ast, env)
  68         f, args = el[1], el[2:end]
  69         if isa(f, MalFunc)
  70             ast = f.ast
  71             env = Env(f.env, f.params, args)
  72             # TCO loop
  73         else
  74             return f(args...)
  75         end
  76     end
  77   end
  78 end
  79
  80 # PRINT
  81 function PRINT(exp)
  82     printer.pr_str(exp)
  83 end
  84
  85 # REPL
  86 repl_env = nothing
  87 function REP(str)
  88     return PRINT(EVAL(READ(str), repl_env))
  89 end
  90
  91 # core.jl: defined using Julia
  92 repl_env = Env(nothing, core.ns)
  93
  94 # core.mal: defined using the language itself
  95 REP("(def! not (fn* (a) (if a false true)))")
  96
  97 while true
  98     line = readline_mod.do_readline("user> ")
  99     if line === nothing break end
 100     try
 101         println(REP(line))
 102     catch e
 103         if isa(e, ErrorException)
 104             println("Error: $(e.msg)")
 105         else
 106             println("Error: $(string(e))")
 107         end
 108         # TODO: show at least part of stack
 109         if !isa(e, StackOverflowError)
 110             bt = catch_backtrace()
 111             Base.show_backtrace(STDERR, bt)
 112         end
 113         println()
 114     end
 115 end