1 files changed, 169 insertions, 0 deletions
diff --git a/python/step9_try.py b/python/step9_try.py
new file mode 100644
index 0000000..e01f42c
--- /dev/null
+++ b/python/step9_try.py
@@ -0,0 +1,169 @@
+import sys, traceback
+import mal_readline
+import mal_types as types
+import reader, printer
+from env import Env
+import core
+
+# read
+def READ(str):
+    return reader.read_str(str)
+
+# eval
+def is_pair(x):
+    return types._sequential_Q(x) and len(x) > 0
+
+def quasiquote(ast):
+    if not is_pair(ast):
+        return types._list(types._symbol("quote"),
+                           ast)
+    elif ast[0] == 'unquote':
+        return ast[1]
+    elif is_pair(ast[0]) and ast[0][0] == 'splice-unquote':
+        return types._list(types._symbol("concat"),
+                           ast[0][1],
+                           quasiquote(ast[1:]))
+    else:
+        return types._list(types._symbol("cons"),
+                           quasiquote(ast[0]),
+                           quasiquote(ast[1:]))
+
+def is_macro_call(ast, env):
+    return (types._list_Q(ast) and
+            types._symbol_Q(ast[0]) and
+            env.find(ast[0]) and
+            hasattr(env.get(ast[0]), '_ismacro_'))
+
+def macroexpand(ast, env):
+    while is_macro_call(ast, env):
+        mac = env.get(ast[0])
+        ast = macroexpand(mac(*ast[1:]), env)
+    return ast
+
+def eval_ast(ast, env):
+    if types._symbol_Q(ast):
+        return env.get(ast)
+    elif types._list_Q(ast):
+        return types._list(*map(lambda a: EVAL(a, env), ast))
+    elif types._vector_Q(ast):
+        return types._vector(*map(lambda a: EVAL(a, env), ast))
+    elif types._hash_map_Q(ast):
+        keyvals = []
+        for k in ast.keys():
+            keyvals.append(EVAL(k, env))
+            keyvals.append(EVAL(ast[k], env))
+        return types._hash_map(*keyvals)
+    else:
+        return ast  # primitive value, return unchanged
+
+def EVAL(ast, env):
+    while True:
+        #print("EVAL %s" % printer._pr_str(ast))
+        if not types._list_Q(ast):
+            return eval_ast(ast, env)
+
+        # apply list
+        ast = macroexpand(ast, env)
+        if not types._list_Q(ast): return ast
+        if len(ast) == 0: return ast
+        a0 = ast[0]
+
+        if "def!" == a0:
+            a1, a2 = ast[1], ast[2]
+            res = EVAL(a2, env)
+            return env.set(a1, res)
+        elif "let*" == a0:
+            a1, a2 = ast[1], ast[2]
+            let_env = Env(env)
+            for i in range(0, len(a1), 2):
+                let_env.set(a1[i], EVAL(a1[i+1], let_env))
+            ast = a2
+            env = let_env
+            # Continue loop (TCO)
+        elif "quote" == a0:
+            return ast[1]
+        elif "quasiquote" == a0:
+            ast = quasiquote(ast[1]);
+            # Continue loop (TCO)
+        elif 'defmacro!' == a0:
+            func = EVAL(ast[2], env)
+            func._ismacro_ = True
+            return env.set(ast[1], func)
+        elif 'macroexpand' == a0:
+            return macroexpand(ast[1], env)
+        elif "py!*" == a0:
+            if sys.version_info[0] >= 3:
+                exec(compile(ast[1], '', 'single'), globals())
+            else:
+                exec(compile(ast[1], '', 'single') in globals())
+            return None
+        elif "try*" == a0:
+            a1, a2 = ast[1], ast[2]
+            if a2[0] == "catch*":
+                try:
+                    return EVAL(a1, env);
+                except Exception as exc:
+                    exc = exc.args[0]
+                    catch_env = Env(env, [a2[1]], [exc])
+                    return EVAL(a2[2], catch_env)
+            else:
+                return EVAL(a1, env);
+        elif "do" == a0:
+            eval_ast(ast[1:-1], env)
+            ast = ast[-1]
+            # Continue loop (TCO)
+        elif "if" == a0:
+            a1, a2 = ast[1], ast[2]
+            cond = EVAL(a1, env)
+            if cond is None or cond is False:
+                if len(ast) > 3: ast = ast[3]
+                else:            ast = None
+            else:
+                ast = a2
+            # Continue loop (TCO)
+        elif "fn*" == a0:
+            a1, a2 = ast[1], ast[2]
+            return types._function(EVAL, Env, a2, env, a1)
+        else:
+            el = eval_ast(ast, env)
+            f = el[0]
+            if hasattr(f, '__ast__'):
+                ast = f.__ast__
+                env = f.__gen_env__(el[1:])
+            else:
+                return f(*el[1:])
+
+# print
+def PRINT(exp):
+    return printer._pr_str(exp)
+
+# repl
+repl_env = Env()
+def REP(str):
+    return PRINT(EVAL(READ(str), repl_env))
+
+# core.py: defined using python
+for k, v in core.ns.items(): repl_env.set(types._symbol(k), v)
+repl_env.set(types._symbol('eval'), lambda ast: EVAL(ast, repl_env))
+repl_env.set(types._symbol('*ARGV*'), types._list(*sys.argv[2:]))
+
+# 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 len(sys.argv) >= 2:
+    REP('(load-file "' + sys.argv[1] + '")')
+    sys.exit(0)
+
+# repl loop
+while True:
+    try:
+        line = mal_readline.readline("user> ")
+        if line == None: break
+        if line == "": continue
+        print(REP(line))
+    except reader.Blank: continue
+    except Exception as e:
+        print("".join(traceback.format_exception(*sys.exc_info())))