def size_to_qty(position_size: float, entry_price: float, precision: int = 3, fee_rate: float = 0) -> float:
"""
converts position-size to quantity
example: requesting $100 at the entry_price of %50 would return 2
:param position_size: float
:param entry_price: float
:param precision: int
:param fee_rate:
:return: float
"""
if math.isnan(position_size) or math.isnan(entry_price):
raise TypeError()
if fee_rate != 0:
position_size = position_size * (1 - fee_rate * 3)
return jh.floor_with_precision(position_size / entry_price, precision)
def test_floor_with_precision():
assert jh.floor_with_precision(1.123) == 1
assert jh.floor_with_precision(1.123, 1) == 1.1
assert jh.floor_with_precision(1.123, 2) == 1.12
assert jh.floor_with_precision(1.123, 3) == 1.123
assert jh.floor_with_precision(1.123, 4) == 1.123
