julia/step3_env.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
   9 # READ
  10 function READ(str)
  11     reader.read_str(str)
  12 end
  13
  14 # EVAL
  15 function eval_ast(ast, env)
  16     if typeof(ast) == Symbol
  17         env_get(env,ast)
  18     elseif isa(ast, Array) || isa(ast, Tuple)
  19         map((x) -> EVAL(x,env), ast)
  20     elseif isa(ast, Dict)
  21         [EVAL(x[1],env) => EVAL(x[2], env) for x=ast]
  22     else
  23         ast
  24     end
  25 end
  26
  27 function EVAL(ast, env)
  28     if !isa(ast, Array) return eval_ast(ast, env) end
  29     if isempty(ast) return ast end
  30
  31     # apply
  32     if     :def! == ast[1]
  33         env_set(env, ast[2], EVAL(ast[3], env))
  34     elseif symbol("let*") == ast[1]
  35         let_env = Env(env)
  36         for i = 1:2:length(ast[2])
  37             env_set(let_env, ast[2][i], EVAL(ast[2][i+1], let_env))
  38         end
  39         EVAL(ast[3], let_env)
  40     else
  41         el = eval_ast(ast, env)
  42         f, args = el[1], el[2:end]
  43         f(args...)
  44     end
  45 end
  46
  47 # PRINT
  48 function PRINT(exp)
  49     printer.pr_str(exp)
  50 end
  51
  52 # REPL
  53 repl_env = Env(nothing,
  54                Dict{Any,Any}(:+ => +,
  55                              :- => -,
  56                              :* => *,
  57                              :/ => div))
  58 function REP(str)
  59     return PRINT(EVAL(READ(str), repl_env))
  60 end
  61
  62 while true
  63     line = readline_mod.do_readline("user> ")
  64     if line === nothing break end
  65     try
  66         println(REP(line))
  67     catch e
  68         if isa(e, ErrorException)
  69             println("Error: $(e.msg)")
  70         else
  71             println("Error: $(string(e))")
  72         end
  73         bt = catch_backtrace()
  74         Base.show_backtrace(STDERR, bt)
  75         println()
  76     end
  77 end