1 files changed, 125 insertions, 0 deletions
diff --git a/python/step7_quote.py b/python/step7_quote.py
new file mode 100644
index 0000000..3054bb0
--- /dev/null
+++ b/python/step7_quote.py
@@ -0,0 +1,125 @@
+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 is_pair(x):
+    return sequential_Q(x) and len(x) > 0
+
+def quasiquote(ast):
+    if not is_pair(ast):
+        return new_list(new_symbol("quote"), ast)
+    elif ast[0] == 'unquote':
+        return ast[1]
+    elif is_pair(ast[0]) and ast[0][0] == 'splice-unquote':
+        return new_list(new_symbol("concat"), ast[0][1], quasiquote(ast[1:]))
+    else:
+        return new_list(new_symbol("cons"), quasiquote(ast[0]), quasiquote(ast[1:]))
+
+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):
+    while True:
+        #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)
+        elif "quote" == a0:
+            return ast[1]
+        elif "quasiquote" == a0:
+            return EVAL(quasiquote(ast[1]), 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 new_function(EVAL, a2, env, a1)
+        else:
+            el = eval_ast(ast, env)
+            f = el[0]
+            if hasattr(f, '__meta__') and f.__meta__.has_key("exp"):
+                m = f.__meta__
+                ast = m['exp']
+                env = Env(m['env'], m['params'], el[1:])
+            else:
+                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)
+
+# Import types functions
+for name, val in types_ns.items(): _ref(name, val)
+
+_ref('read-string', read_str)
+_ref('eval', lambda ast: EVAL(ast, repl_env))
+_ref('slurp', lambda file: open(file).read())
+_ref('slurp-do', lambda file: "(do" + open(file).read() + ")") 
+
+# Defined using the language itself
+REP("(def! not (fn* (a) (if a false true)))")
+REP("(def! load-file (fn* (f) (eval (read-string (slurp-do f)))))")
+
+if len(sys.argv) >= 2:
+    REP('(load-file "' + sys.argv[1] + '")')
+else:
+    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()))