Downloading apps for mac and iphone?

Hello. Just had a random question...

If I were to download an app on my iphone, I could log into my account of my ipod touch and download the same app for free because I bought it with that account. What about if I buy an app on my macbook pro appstore? It is available for both the macbook pro and the iphone, so will I be able to download it onto my iphone without paying for it a second time?