tools/maths

#!/usr/bin/env python3

import sys
import operator
from functools import reduce as fold
import argparse


product = lambda xs: fold(operator.mul, xs)
operators = {
	"sum": sum, "+": sum,
	"mul": product, "product": product, "prod": product, "*": product,
	"max": max,
	"min": min
}
default_operator = "+"


parser = argparse.ArgumentParser(description="Do maths on stdin")
parser.add_argument(
	"operator",
	metavar="op",
	nargs='?',
	choices=list(operators.keys()),
	default=default_operator,
	help="Action to take (one of: {}; default: {})".format(
		", ".join(operators.keys()),
		default_operator
	)
)
parser.add_argument(
	"--int",
	dest="datatype",
	action="store_const",
	const=(int, "integer"),
	default=(float, "decimal number"),
	help="use integers (default: float)"
)
args = parser.parse_args()


op = operators[args.operator]
parse_func, datatype_name = args.datatype

data = []
for i, line in enumerate(sys.stdin, start=1):
	if line == "\n":
		continue
	try:
		data.append(parse_func(line))
	except ValueError:
		print("Line {} could not be interpreted as a {}: {:r}".format(i, datatype_name, line.rstrip("\n")))
		sys.exit(3)

print(op(data))