julia/step2_eval.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
   8 # READ
   9 function READ(str)
  10     reader.read_str(str)
  11 end
  12
  13 # EVAL
  14 function eval_ast(ast, env)
  15     if typeof(ast) == Symbol
  16         env[ast]
  17     elseif isa(ast, Array) || isa(ast, Tuple)
  18         map((x) -> EVAL(x,env), ast)
  19     elseif isa(ast, Dict)
  20         [EVAL(x[1],env) => EVAL(x[2], env) for x=ast]
  21     else
  22         ast
  23     end
  24 end
  25
  26 function EVAL(ast, env)
  27     if !isa(ast, Array) return eval_ast(ast, env) end
  28     if isempty(ast) return ast end
  29
  30     # apply
  31     el = eval_ast(ast, env)
  32     f, args = el[1], el[2:end]
  33     f(args...)
  34 end
  35
  36 # PRINT
  37 function PRINT(exp)
  38     printer.pr_str(exp)
  39 end
  40
  41 # REPL
  42 repl_env = Dict{Any,Any}(:+ => +,
  43                          :- => -,
  44                          :* => *,
  45                          :/ => div)
  46 function REP(str)
  47     return PRINT(EVAL(READ(str), repl_env))
  48 end
  49
  50 while true
  51     line = readline_mod.do_readline("user> ")
  52     if line === nothing break end
  53     try
  54         println(REP(line))
  55     catch e
  56         if isa(e, ErrorException)
  57             println("Error: $(e.msg)")
  58         else
  59             println("Error: $(string(e))")
  60         end
  61         bt = catch_backtrace()
  62         Base.show_backtrace(STDERR, bt)
  63         println()
  64     end
  65 end