--- step4_if_fn_do ------------------------------ import types, reader, printer, env, core READ(str): return reader.read_str(str) 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): if not list?(ast): return eval_ast(ast, env) if empty?(ast): return ast switch ast[0]: 'def!: return env.set(ast[1], EVAL(ast[2], env)) 'let*: let_env = ...; return EVAL(ast[2], let_env) 'do: return eval_ast(rest(ast), env)[-1] 'if: return EVAL(EVAL(ast[1], env) ? ast[2] : ast[3], env) 'fn*: return (...a) -> EVAL(ast[2], new Env(env, ast[1], a)) _default_: f, args = eval_ast(ast, env) 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))) ;; core.mal: defined using the language itself rep("(def! not (fn* (a) (if a false true)))") 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(" ")), '<: lt, '<=: lte, '>: gt, '>=: gte, '+: add, '-: sub, '*: mult, '/: div, 'list: list, 'list?: list?, 'empty?: empty?, 'count: count}