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fpd.py
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fpd.py
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import string, sys, copy
from pprint import pprint, pformat
DEBUG = False
def next_closing_brace(e, i):
level = 0
while i < len(e):
if e[i] == '}':
if level == 0:
return i
else:
level -= 1
elif e[i] == '{':
level += 1
i += 1
# should not be reached
raise SyntaxError("Unbalanced parenthesis at", i)
def next_closing_parenthesis(e, i):
level = 0
while i < len(e):
if e[i] == ')':
if level == 0:
return i
else:
level -= 1
elif e[i] == '(':
level += 1
i += 1
# should not be reached
raise SyntaxError("Unbalanced parenthesis at", i)
def rescue_lambdas(s):
i = -1
try:
while True:
i = s.index('->', i+1)+2
if s[i + (1 if s[i] == ' ' else 0)] != '(':
j = next_closing_parenthesis(s, i)
s = s[:i] + '(' + s[i:j] + ')' + s[j:]
except ValueError: # .index returns ValueError: substring not found
return s
def recursive_replace_empty_lists_with_empty_dicts(l):
for n, i in enumerate(l):
if i == []:
l[n] = {}
if type(i) is list:
l[n] = recursive_replace_empty_lists_with_empty_dicts(l[n])
return l
def parse(s):
s = ' '.join(s.split())
s = s.replace("{}", "()").replace("{ }", "()")
if '=' in s:
s = s.replace(',', ')').replace('=', '=(').replace('}', ')}').replace(" =", "=")
s = s.replace("(())", "()")
s = rescue_lambdas(s)
if s[0] != '(' or s[-1] != ')':
s = '(' + s + ')'
if s[1] == '{':
i = next_closing_brace(s, 2)+1
s = s[:i] + '(' + s[i:] + ')'
ast = s.replace('(', ' ( '). \
replace(')', ' ) '). \
replace('{', ' { '). \
replace('}', ' } '). \
replace('=', '= '). \
split()
#print(ast)
e = parse_tokens(ast)
return recursive_replace_empty_lists_with_empty_dicts(e)
def parse_tokens(e):
t = e.pop(0)
if t == '{':
r = []
while e[0] != '}':
r.append(parse_tokens(e))
e.pop(0)
return r
elif t == '(':
r = []
while e[0] != ')':
r.append(parse_tokens(e))
e.pop(0)
return r
else:
try:
return int(t)
except ValueError:
return t
environment = {
'plus': lambda a, b: a + b,
'minus': lambda a, b: a - b,
'mult': lambda a, b: a * b,
'div': lambda a, b: a / b,
'cond': "nani?" #a: value is never used, key is
}
class Lamb:
def __init__(self, variable_name, body, env):
self.variable_name = variable_name
self.body = body
self.env = env
def __repr__(self):
return self.__str__()
def __str__(self):
return "Lambda: " + self.variable_name + "->" + str(self.body)
def recursive_replace(l, a, b):
for n, i in enumerate(l):
if type(i) is list:
l[n] = recursive_replace(l[n], a, b)
elif type(i) is str and i == a:
l[n] = b
return l
exnum = 0
def evaluate(e, env=environment):
global exnum
if DEBUG:
print(f"{exnum:04d}: ")
print(pformat(e, width=160))
exnum += 1
if e == []:
return e
if isinstance(e, list) and len(e) == 1:
return evaluate(e[0], env)
if isinstance(e, str):
if '->' in e:
return e[0:e.index('->')]
elif e in env and e not in environment:
return env[e]
return e
if isinstance(e, list) and len(e) == 2:
try: # NOTE: this is how i set the environment rn :/
if '=' in e[0][0]: # is there a more general rule
new_env = evaluate(e[0], env) # this feels hacks
return evaluate(e[1], {**env, **new_env})
except:
pass
if isinstance(e, int) or isinstance(e, Lamb) or isinstance(e, dict):
return e
if isinstance(e[0], Lamb) and (isinstance(e[1], int) or isinstance(e[1], dict) or e[1] == []):
body_copy = copy.deepcopy(e[0].body) # what for? strings are immutable #a: we change list not string
new_body = recursive_replace(body_copy, e[0].variable_name, e[1])
return evaluate([evaluate(new_body, env)] + e[2:], env)
if isinstance(e[0], str):
if '->' in e[0]:
variable_name = evaluate(e[0], env)
body = e[1]
if len(e) > 2:
return evaluate([Lamb(variable_name, body, env)] + e[2:])
return Lamb(variable_name, body, env)
elif e[0] in environment:
if len(e) == 3:
return environment[e[0]](evaluate(e[1], env), evaluate(e[2], env))
if e[0] == 'cond' and len(e) == 4:
c = evaluate(e[1], env)
if c == 0 or c == {}:
return evaluate(e[3], env)
return evaluate(e[2], env)
elif '=' in e[0]:
assert len(e) % 2 == 0
r = {}
for i in range(0, len(e), 2):
name = e[i][:-1]
value = evaluate(e[i + 1], {**env, **r})
r[name] = value
return r
if isinstance(e[0], dict) and len(e) == 2:
return evaluate(e[1], {**env, **e[0]})
if isinstance(e, list):
a = []
d = False
for b in e:
c = evaluate(b, env)
a.append(c)
if b != c:
d = True
return evaluate(a, env) if d else a
if __name__ == "__main__":
test = True
if test:
assert(evaluate(parse("(x->y->plus(mult x x)y) 2 3")) == 7)
assert(evaluate(parse("((x->(y->plus(mult x x)y))2)3")) == 7)
assert(evaluate(parse("minus ((y->plus(mult 2 2)y)5)7")) == 2)
assert(evaluate(parse("{a=x->y->plus(mult x x)y, b=a 2, c=b 3}minus(b 5)c")) == 2)
assert(evaluate(parse("cond 14 2 3")) == 2)
assert(evaluate(parse("cond 0 2 3")) == 3)
assert(evaluate(parse("cond {} 2 3")) == 3)
assert evaluate(parse("{fac=x->(cond x (mult x(fac (minus x 1))) 1)} fac 10")) == 3628800
# whiterock's tests taken from alternate.py
assert evaluate(parse("{A=5, B=x->(plus A x)} B 11")) == 16
assert evaluate(parse("{A=5, B=x->(plus A x)} B A")) == 10
assert evaluate(parse("{A=8, B={C=3}} B C")) == 3
assert evaluate(parse("x->(x A) {A=5}")) == 5
assert evaluate(parse("""{
append= x->y->cond x {head=x head, tail=append(x tail)y} y,
gen=x->cond x (append(gen(minus x 1)) {head=x, tail={}}) {}
}
gen 3""")) == {'head': 1, 'tail': {'head': 2, 'tail': {'head': 3, 'tail': {}}}}
if len(sys.argv) != 2:
print("Please provide a file name to open!")
exit()
p = sys.argv[1]
with open(p, "r") as fh:
print(evaluate(parse(fh.read())))