Quote from: phantomcircuit on July 31, 2011, 08:43:47 PM

When you buy AAPL from your broker they are actually giving you a quoted price. That is a price which is good for a certain amount of time and which they are guaranteeing themselves. They pay for this with a small fee (actually sometimes not so small).

Implementing this on a bitcoin exchange is both more difficult and more risky than the underlying exchange software, mostly because acting as a broker has significant legal implications where as exchanging currency for virtual goods does not.

I think you're missing the point - he doesn't want a quote or anything like that... he just wants the exchange to figure out the appropriate order size to deplete a given amount of funds. Whether the orders fill or not, I don't think anyone in support of this idea really gives a shit.

FWIW, this is only really needed on TradeHill et all - on MtGox as long as you shoot the moon on your quantity, it'll figure it out for you... it'll make two orders, one which can fill and one which can't because of insufficient funds. If you wanna buy $100 worth of BTC at $13, simply put say 10BTC in the quantity field, then cancel the order which isn't actually on the books because of insufficient funds.

On TH though, it's a pain in the arse. Figuring out how much BTC to buy to deplete a given amount of USD either involves a calculator or brute-force guessing.