Is it normal Taking a calculator when you shop?

I'm from the same batch, but as a computer scientist I quickly adopt new tech.

Plus my phones calculator is far more advanced than the TI graphical calculators.

Plus I never buy something in a store without checking the online prices with my phone. I only buy something in a store when it is cheaper.

Or better this decides if I buy it in a store or not:

((storePrice-deliveryCost)*rareItemFactor))<=(onlinePrice+patienceCost*(deliveryTime^deliveryFactor))

With usually but depending on mood and item:
rareItemFactor = 1;
patienceCost = 1.5;
deliveryFactor = 1.8;