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
  29     # apply
  30     el = eval_ast(ast, env)
  31     f, args = el[1], el[2:end]
  32     f(args...)
  33 end
  34
  35 # PRINT
  36 function PRINT(exp)
  37     printer.pr_str(exp)
  38 end
  39
  40 # REPL
  41 repl_env = Dict{Any,Any}(:+ => +,
  42                          :- => -,
  43                          :* => *,
  44                          :/ => div)
  45 function REP(str)
  46     return PRINT(EVAL(READ(str), repl_env))
  47 end
  48
  49 while true
  50     line = readline_mod.do_readline("user> ")
  51     if line === nothing break end
  52     try
  53         println(REP(line))
  54     catch e
  55         if isa(e, ErrorException)
  56             println("Error: $(e.msg)")
  57         else
  58             println("Error: $(string(e))")
  59         end
  60         bt = catch_backtrace()
  61         Base.show_backtrace(STDERR, bt)
  62         println()
  63     end
  64 end