--- step8_macros -------------------------------- import types, reader, printer, env, core READ(str): return reader.read_str(str) pair?(ast): return ... // true if non-empty sequence quasiquote(ast): return ... // quasiquote macro?(ast, env): return ... // true if macro call macroexpand(ast, env): return ... // recursive macro expansion eval_ast(ast,env): switch type(ast): symbol: return env.get(ast) list,vector: return ast.map((x) -> EVAL(x,env)) hash: return ast.map((k,v) -> list(k, EVAL(v,env))) _default_: return ast EVAL(ast,env): while true: if not list?(ast): return eval_ast(ast, env) ast = macroexpand(ast, env) if not list?(ast): return eval_ast(ast, env) switch ast[0]: 'def!: return env.set(ast[1], EVAL(ast[2], env)) 'let*: env = ...; ast = ast[2] // TCO 'quote: return ast[1] 'quasiquote: ast = quasiquote(ast[1]) // TCO 'defmacro!: return ... // like def!, but set macro property 'macroexpand: return macroexpand(ast[1], env) 'do: ast = eval_ast(ast[1..-1], env)[-1] // TCO 'if: EVAL(ast[1], env) ? ast = ast[2] : ast = ast[3] // TCO 'fn*: return new MalFunc(...) _default_: f, args = eval_ast(ast, env) if malfunc?(f): ast = f.fn; env = ... // TCO else: return apply(f, args) PRINT(exp): return printer.pr_str(exp) repl_env = new Env() rep(str): return PRINT(EVAL(READ(str),repl_env)) ;; core.EXT: defined using Racket core.ns.map((k,v) -> (repl_env.set(k, v))) repl_env.set('eval, (ast) -> EVAL(ast, repl-env)) repl_env.set('*ARGV*, cmdline_args[1..]) ;; core.mal: defined using the language itself rep("(def! not (fn* (a) (if a false true)))") rep("(def! load-file (fn* (f) (eval (read-string (str \"(do \" (slurp f) \")\")))))") rep("(defmacro! cond (fn* (& xs) (if (> (count xs) 0) (list 'if (first xs) (if (> (count xs) 1) (nth xs 1) (throw \"odd number of forms to cond\")) (cons 'cond (rest (rest xs)))))))"); rep("(defmacro! or (fn* (& xs) (if (empty? xs) nil (if (= 1 (count xs)) (first xs) `(let* (or_FIXME ~(first xs)) (if or_FIXME or_FIXME (or ~@(rest xs))))))))"); if cmdline_args: rep("(load-file \"" + args[0] + "\")"); exit 0 main loop: try: println(rep(readline("user> "))) catch e: println("Error: ", e) --- env module ---------------------------------- class Env (outer=null,binds=[],exprs=[]) data = hash_map() foreach b, i in binds: if binds[i] == '&: data[binds[i+1]] = exprs.drop(i); break else: data[binds[i]] = exprs[i] set(k,v): return data.set(k,v) find(k): return data.has(k) ? this : (if outer ? find(outer) : null) get(k): return data.find(k).get(k) OR raise "'" + k + "' not found" --- core module --------------------------------- ns = {'=: equal?, 'pr-str: (a) -> a.map(|s| pr_str(e,true)).join(" ")), 'str: (a) -> a.map(|s| pr_str(e,false)).join("")), 'prn: (a) -> println(a.map(|s| pr_str(e,true)).join(" ")), 'println: (a) -> println(a.map(|s| pr_str(e,false)).join(" ")), 'read-string: read_str, 'slurp read-file, '<: lt, '<=: lte, '>: gt, '>=: gte, '+: add, '-: sub, '*: mult, '/: div, 'list: list, 'list?: list?, 'cons: (a) -> concat([a[0]], a[1]), 'concat: (a) -> reduce(concat, [], a), 'nth: (a) -> a[0][a[1]] OR raise "nth: index out of range", 'first: (a) -> a[0][0] OR nil, 'rest: (a) -> a[0][1..] OR list(), 'empty?: empty?, 'count: count, 'atom: (a) -> new Atom(a[0]), 'atom?: (a) -> type(a[0]) == "atom", 'deref: (a) -> a[0].val, 'reset!: (a) -> a[0].val = a[1], 'swap!: swap!}