1 files changed, 76 insertions, 0 deletions
diff --git a/python/step3_env.py b/python/step3_env.py
new file mode 100644
index 0000000..f95a978
--- /dev/null
+++ b/python/step3_env.py
@@ -0,0 +1,76 @@
+import sys, traceback
+import mal_readline
+from mal_types import (pr_str, sequential_Q, symbol_Q, coll_Q, list_Q,
+                       vector_Q, hash_map_Q, new_symbol, new_function,
+                       new_list, new_vector, new_hash_map, Env, types_ns)
+from reader import (read_str, Blank)
+
+# read
+def READ(str):
+    return read_str(str)
+
+# eval
+def eval_ast(ast, env):
+    if symbol_Q(ast):
+        return env.get(ast)
+    elif list_Q(ast):
+        return new_list(*map(lambda a: EVAL(a, env), ast))
+    elif vector_Q(ast):
+        return new_vector(*map(lambda a: EVAL(a, env), ast))
+    elif hash_map_Q(ast):
+        keyvals = []
+        for k in ast.keys():
+            keyvals.append(EVAL(k, env))
+            keyvals.append(EVAL(ast[k], env))
+        return new_hash_map(*keyvals)
+    else:
+        return ast  # primitive value, return unchanged
+
+def EVAL(ast, env):
+    #print("EVAL %s" % ast)
+    if not list_Q(ast):
+        return eval_ast(ast, env)
+
+    # apply list
+    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))
+        return EVAL(a2, let_env)
+    else:
+        el = eval_ast(ast, env)
+        f = el[0]
+        return f(*el[1:])
+
+# print
+def PRINT(exp):
+    return pr_str(exp)
+
+# repl
+repl_env = Env()
+def REP(str):
+    return PRINT(EVAL(READ(str), repl_env))
+def _ref(k,v): repl_env.set(k, v)
+
+_ref('+', lambda a,b: a+b)
+_ref('-', lambda a,b: a-b)
+_ref('*', lambda a,b: a*b)
+_ref('/', lambda a,b: a/b)
+
+while True:
+    try:
+        line = mal_readline.readline("user> ")
+        if line == None: break
+        if line == "": continue
+        print(REP(line))
+    except Blank: continue
+    except Exception as e:
+        print "".join(traceback.format_exception(*sys.exc_info()))