Currency Question

Can someone explain to me why when they say if you long a call in the price it is equal to long a put in the base?

If you give me USD for GBP have you bought GBP (with USD) or sold USD (for GBP)?

Put another way, when you (mistakenly) think that you own a call option on GOOG (priced in USD), what you _ really _ own is a put option on USD (priced in GOOG).

that’s a little bit of a mind-bender right there sir magician!

I think this helpful especially in the currencies section (i think reading 19 in asset allocation) where they invert the D/F notation to F/D so you have to think about it in terms of the opposite position (I believe it’s blue box 6 and 8 off the top of my head)