First: yes, i have taken a very long look at Norvig's lispy. Second: I have reused part of his code.
On to my code, and my question. I am writing a really non-idiomatic lisp interpreter in Python, and I'm curious as to how I would write nested function definitions (e.g. (define square (lambda (x) (* x x))) then (define SoS (lambda (x y) (+ (square x) (square y))))) and currently that doesn't work. I'm a bit stuck. What can I do?
EDIT: Any tips about my coding style or improvements I could make would be greatly appreciated. Thank you!
"""
FIX NESTED DEFINITIONS!
(def square (lambda (x) (* x x)))
(def SoS (lambda x y) (+ (square x) (square y)))
DOES NOT WORK!
"""
#!/usr/bin/python
import readline, sys, shlex
userFuncs = {}
userVars = {}
stdOps = "% * / - + set!".split()
def lispify(nested_lists):
return str(nested_lists).replace('[','(').replace(']',')').replace(', ',' ').replace("'",'')
def mul_arr(array):
tot = 1
for i in array: tot *= i
return tot
def div_arr(array):
tot = array[0]
for i in array[1:]: tot /= i
return tot
def sub_arr(array):
print array
if len(array) > 1: tot = array[0]
else: tot = 0-array[0]
for i in array[1:]: tot -= i
return tot
def atom(tok):
try: return int(tok)
except:
try: return float(tok)
except: return str(tok)
def pre_in(read):
tempOp = read[0]
body = read[1:]
expr = []
for i in range(len(body)-1):
if not isinstance(body[i], list) and body[i] != " ":
expr.append(str(body[i]))
expr.append(tempOp)
else:
expr.append(str(pre_in(body[i])))
expr.append(tempOp)
try:
if not isinstance(body[-1], list): expr.append(str(body[-1]))
else: expr.append(str(pre_in(body[-1])))
except: pass
if expr != None: return "("+' '.join(expr)+")"
def tok(s):
try: return shlex.split(s.replace('(',' ( ').replace(')',' ) '))
except: return s.replace('(',' ( ').replace(')',' ) ').split()
def read_from(toks):
if len(toks) == 0: raise SyntaxError('unexpected EOF')
tok = toks.pop(0)
if tok == "'":
l = []
toks.pop(0)
while toks[0] != ")": l.append(read_from(toks))
toks.pop(0)
return lispify(l)
if tok == '(':
l = []
while toks[0] != ')': l.append(read_from(toks))
toks.pop(0)
return l
elif tok == ')': raise SyntaxError('unexpected \')\'')
else: return atom(tok)
def total_eval(read):
if isinstance(read, int):
return read
elif isinstance(read, str):
if read not in stdOps:
if read in userVars:
return atom(userVars[read])
else:
return str(atom(read))
elif isinstance(read, list):
if read[0] in userFuncs:
print read[0]+" = "+userFuncs[read[0]]
exec(read[0]+" = "+userFuncs[read[0]])
return eval(read[0]+str(tuple(read[1:])))
elif read[0] == "+":
return sum([float(total_eval(i)) for i in read[1:]])
elif read[0] == "*":
return mul_arr([float(total_eval(i)) for i in read[1:]])
elif read[0] == "/":
return div_arr([float(total_eval(i)) for i in read[1:]])
elif read[0] == "-":
return sub_arr([float(total_eval(i)) for i in read[1:]])
elif read[0] == "set!" or read[0] == "setf":
userVars[read[1]] = total_eval(read[2])
return "ok"
elif read[0] == "lambda":
tempvars = ','.join(i.replace(',','') for i in read[1])
expr = read[2]
return "lambda "+str(tempvars)+": "+pre_in(expr)
elif read[0] == "def" or read[0] == "define" or read[0] == "defun":
funcName = read[1]
funcBody = read[2]
userFuncs[funcName] = total_eval(funcBody)
return "ok"
elif read[0] == "cons":
body = read[1:]
arr = body[0]
to_push = body[1]
if not isinstance(arr, list):
arr = [arr]
for i in to_push:
arr.append(i)
return lispify(arr)
elif read[0] == "append":
body = read[1:]
main = body[0]
tail = body[1:]
for i in tail:
if i != []:
main.append(i)
#print main
return lispify(main)
elif read[0] == "list":
return lispify(str([total_eval(read[1:][i]) for i in range(len(read[1:]))]))
elif read[0] == "\'" or read[0] == "quote":
return lispify(read[1:][0])
elif read[0] == "print":
return total_eval(read[1:][0])
elif not isinstance(read[0], list):
if read[0] in userFuncs:
args = read[1:]
exec(read[0]+" = "+userFuncs[read[0]])
return eval(read[0]+str(tuple([float(i) for i in args])))
else:
if read[0][0] == "lambda":
tempvars = ','.join(i.replace(',','') for i in read[0][1])
expr = read[0][2]
exec("temp = lambda "+str(tempvars)+": "+str(pre_in(expr)))
args = read[1:] if len(read[1:]) > 1 else read[1]
if isinstance(args, list): return eval("temp"+str(tuple([total_eval(i) for i in args])))
else: return eval("temp("+str(float(args))+")")
"""
while 1:
try:
a = raw_input("lisp> ")
try:
print tok(a)
print read_from(tok(a))
print total_eval(read_from(tok(a))),"\n"
except:
errorMsg = str(sys.exc_info()[1]).split()
if errorMsg[0] == "list":
print "ParseError: mismatched parentheses\n"
else:
print ' '.join(errorMsg)
print
except (EOFError, KeyboardInterrupt):
print "\nbye!"
break
"""
while 1:
a = raw_input("lisp> ")
#print tok(a)
#print read_from(tok(a))
print total_eval(read_from(tok(a)))
print
#"""
