calc v2

calc4-2.py

#!/usr/bin/python3.7
from functools import reduce
push_to_stack=object()

stack=[]
OP="+/-*"
all_true=lambda x: True

def crush_stack():
    global stack
    stack=stack[:1]
    print("=%d" % stack[0])


dispatch={
    all_true: print,
    lambda st : st.isdigit() or st[0] in '+-' and st[1:].isdigit():
        lambda x: stack.append(int(x)),
    lambda x: x in OP:
        lambda op: stack.insert(
                        0,
                        int(reduce(
                            { '+' : int.__add__,
                              '*' : int.__mul__,
                              '-' : int.__sub__, 
                              '/':int.__truediv__}[op],
                            stack
                        )
                    )) or crush_stack,
}

def tokenize(stream):
    print(stream)
    buff=""
    for c in stream:
        if c in OP:
            if buff: yield buff
            buff=c
        elif c in "0123456789":
            buff+=c
        else:
            if buff:
                yield buff
                buff=""
    if buff: yield buff


PRED=0
ACTION=1

update_state = lambda stream: list(map(
        lambda el: any(map(
            lambda guide: guide[PRED](el) and guide[ACTION](el) is crush_stack,
            dispatch.items())) and crush_stack(), ## or print(stack), # debug
        tokenize(stream)
    ))

update_state("1 -20 +3 + 2 / 4 1 1 + -1 OOOO A O 1 +")
stack.clear()
update_state('10 1 + 0 * 2 32 + 13 * 2 - 2 / 7 / 1 +')
print(stack)
update_state("1 +")
print(stack)