gen_digit_packing.py

import sys


def gen_digit_packing(a_val, b_val):
    a = var("a")
    b = var("b")
    out = var("out")

    p = []
    p.extend(assign(a, a_val))
    p.extend(assign(b, b_val))
    p.extend(assign(out, 0))

    for _ in range(4):
        p.extend(assign(a, shift_right(a)))
        p.extend(assign(b, shift_right(b)))

    for _ in range(4):
        p.extend(modulo(a, 10))
        p.extend(assign(a, shift_right(a)))
        p.extend(assign(out, binop(out, "*", 10)))
        p.extend(assign(out, binop(out, "+", retvar())))

        p.extend(modulo(b, 10))
        p.extend(assign(b, shift_right(b)))
        p.extend(assign(out, binop(out, "*", 10)))
        p.extend(assign(out, binop(out, "+", retvar())))

    p.extend(debug(a))
    p.extend(debug(b))
    p.extend(debug(out))

    return p


# -----------------------------------#


def var(name):
    # vars are just strings
    return name


def retvar():
    return var("ret")


def tmpvar(tmpcounter=[0]):
    tmpcounter[0] += 1
    return var(f"tmp{tmpcounter[0]}")


def binop(expr1, op, expr2):
    # expressions return strings
    return f"{expr1} {op} {expr2}"


def assign(var, expr):
    # statements return lists
    return [f"{var} = {expr}"]


def shift_right(var, n=1):
    return binop(var, "//", 10)  # n.b. rounding integer divide


def modulo(var, expr):
    # returns value in retvar
    tmp = tmpvar()
    return (
        assign(tmp, shift_right(var))
        + assign(tmp, binop(tmp, "*", 10))
        + assign(retvar(), binop(var, "-", tmp))
    )


def debug(var):  # easy way to see the values when running code as python
    return ["print(f'{" + var + "=}')"]


def output_program(program):
    for line in program:
        print(line)
    print()


if __name__ == "__main__":
    if len(sys.argv) == 3:
        a, b = map(int, sys.argv[1:3])
    else:
        a, b = 24680000, 13570000

    output_program(gen_digit_packing(a, b))