julia/step4_if_fn_do.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
  10 # READ
  11 function READ(str)
  12     reader.read_str(str)
  13 end
  14
  15 # EVAL
  16 function eval_ast(ast, env)
  17     if typeof(ast) == Symbol
  18         env_get(env,ast)
  19     elseif isa(ast, Array) || isa(ast, Tuple)
  20         map((x) -> EVAL(x,env), ast)
  21     elseif isa(ast, Dict)
  22         [EVAL(x[1],env) => EVAL(x[2], env) for x=ast]
  23     else
  24         ast
  25     end
  26 end
  27
  28 function EVAL(ast, env)
  29     if !isa(ast, Array) return eval_ast(ast, env) 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     elseif :do == ast[1]
  41         eval_ast(ast[2:end], env)[end]
  42     elseif :if == ast[1]
  43         cond = EVAL(ast[2], env)
  44         if cond === nothing || cond === false
  45             if length(ast) >= 4
  46                 EVAL(ast[4], env)
  47             else
  48                 nothing
  49             end
  50         else
  51             EVAL(ast[3], env)
  52         end
  53     elseif symbol("fn*") == ast[1]
  54         (args...) -> EVAL(ast[3], Env(env, ast[2], args))
  55     else
  56         el = eval_ast(ast, env)
  57         f, args = el[1], el[2:end]
  58         f(args...)
  59     end
  60 end
  61
  62 # PRINT
  63 function PRINT(exp)
  64     printer.pr_str(exp)
  65 end
  66
  67 # REPL
  68 repl_env = nothing
  69 function REP(str)
  70     return PRINT(EVAL(READ(str), repl_env))
  71 end
  72
  73 # core.jl: defined using Julia
  74 repl_env = Env(nothing, core.ns)
  75
  76 # core.mal: defined using the language itself
  77 REP("(def! not (fn* (a) (if a false true)))")
  78
  79 while true
  80     line = readline_mod.do_readline("user> ")
  81     if line === nothing break end
  82     try
  83         println(REP(line))
  84     catch e
  85         if isa(e, ErrorException)
  86             println("Error: $(e.msg)")
  87         else
  88             println("Error: $(string(e))")
  89         end
  90         if !isa(e, StackOverflowError)
  91             bt = catch_backtrace()
  92             Base.show_backtrace(STDERR, bt)
  93         end
  94         println()
  95     end
  96 end