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forth3.py
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memory = ["input goes here", "exit"]
data_stack = []
call_stack = []
def return_():
call_stack.pop()
def exit_():
del call_stack[:]
names = {"push1": lambda: (1,),
"print": lambda x: print(x),
"return": return_,
"exit": exit_}
def main_loop():
while True:
if not call_stack:
return
#print("call stack: %s\ndata stack: %s\nmemory: %s\n\n" % (call_stack, data_stack, memory))
#print("names: %s" % names)
#print("next command: %s" % memory[call_stack[-1]])
func = names[memory[call_stack[-1]]] # Steps 1, 2, 3
call_stack[-1] += 1 # Step 4
# Step 5 Python functions are primitives, strings (function names) are non-primitives.
if callable(func):
# Deduce number of arguments.
argindex = len(data_stack) - func.__code__.co_argcount
args = data_stack[argindex:]
del data_stack[argindex:]
data_stack.extend(func(*args) or ())
else:
call_stack.append(func) # Step 6
def input_loop():
while True:
for command in input("> ").split():
memory[0] = command
call_stack.append(0)
main_loop()
if __name__ == "__main__":
input_loop()