"""A *very* simple command-line accountant's calculator.
Uses the decimal package (introduced in Python 2.4) for calculation accuracy.
Input should be a number (decimal point is optional), an optional space, and an
operator (one of /, *, -, or +). A blank line will output the total.
Inputting just 'q' will output the total and quit the program.
"""
import decimal
import re
parse_input = re.compile(r'(?P<num_text>\d*(\.\d*)?)\s*(?P<op>[/*\-+])')
total = decimal.Decimal('0')
total_line = lambda val: ''.join(('=' * 5, '\n', str(val)))
while True:
tape_line = raw_input()
if not tape_line:
print total_line(total)
continue
elif tape_line is 'q':
print total_line(total)
break
try:
num_text, space, op = parse_input.match(tape_line).groups()
except AttributeError:
raise ValueError("invalid input")
num = decimal.Decimal(num_text)
if op is '/':
total /= num
elif op is '*':
total *= num
elif op is '-':
total -= num
elif op is '+':
total += num
else:
raise ValueError("unsupported operator: %s" % op)
