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mal/python/step2_eval.py

64 lines
1.6 KiB
Python

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):
try:
return env[ast]
except:
raise Exception("'" + ast + "' not found")
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
el = eval_ast(ast, env)
f = el[0]
return f(*el[1:])
def PRINT(exp):
return pr_str(exp)
# repl
repl_env = {}
def REP(str):
return PRINT(EVAL(READ(str), repl_env))
repl_env['+'] = lambda a,b: a+b
repl_env['-'] = lambda a,b: a-b
repl_env['*'] = lambda a,b: a*b
repl_env['/'] = 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()))