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     if isempty(ast) return ast end
  31
  32     # apply
  33     if     :def! == ast[1]
  34         env_set(env, ast[2], EVAL(ast[3], env))
  35     elseif symbol("let*") == ast[1]
  36         let_env = Env(env)
  37         for i = 1:2:length(ast[2])
  38             env_set(let_env, ast[2][i], EVAL(ast[2][i+1], let_env))
  39         end
  40         EVAL(ast[3], let_env)
  41     elseif :do == ast[1]
  42         eval_ast(ast[2:end], env)[end]
  43     elseif :if == ast[1]
  44         cond = EVAL(ast[2], env)
  45         if cond === nothing || cond === false
  46             if length(ast) >= 4
  47                 EVAL(ast[4], env)
  48             else
  49                 nothing
  50             end
  51         else
  52             EVAL(ast[3], env)
  53         end
  54     elseif symbol("fn*") == ast[1]
  55         (args...) -> EVAL(ast[3], Env(env, ast[2], Any[args...]))
  56     else
  57         el = eval_ast(ast, env)
  58         f, args = el[1], el[2:end]
  59         f(args...)
  60     end
  61 end
  62
  63 # PRINT
  64 function PRINT(exp)
  65     printer.pr_str(exp)
  66 end
  67
  68 # REPL
  69 repl_env = nothing
  70 function REP(str)
  71     return PRINT(EVAL(READ(str), repl_env))
  72 end
  73
  74 # core.jl: defined using Julia
  75 repl_env = Env(nothing, core.ns)
  76
  77 # core.mal: defined using the language itself
  78 REP("(def! not (fn* (a) (if a false true)))")
  79
  80 while true
  81     line = readline_mod.do_readline("user> ")
  82     if line === nothing break end
  83     try
  84         println(REP(line))
  85     catch e
  86         if isa(e, ErrorException)
  87             println("Error: $(e.msg)")
  88         else
  89             println("Error: $(string(e))")
  90         end
  91         if !isa(e, StackOverflowError)
  92             bt = catch_backtrace()
  93             Base.show_backtrace(STDERR, bt)
  94         end
  95         println()
  96     end
  97 end