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Title: Why add/subtract 0.5 while converting between JSON and amount Post by: Farghaly on January 30, 2014, 11:38:54 AM In this wiki article "Proper Money Handling"
https://en.bitcoin.it/wiki/Proper_Money_Handling_(JSON-RPC) Why add 0.5 if value is more than 0.0, and subtract 0.5 if value less than 0.0 ??? Code: int64_t JSONtoAmount(double value) {Title: Re: Why add/subtract 0.5 while converting between JSON and amount Post by: deepceleron on January 30, 2014, 02:43:01 PM In this wiki article "Proper Money Handling" https://en.bitcoin.it/wiki/Proper_Money_Handling_(JSON-RPC) Why add 0.5 if value is more than 0.0, and subtract 0.5 if value less than 0.0 ??? Code: int64_t JSONtoAmount(double value) {This is a way to achieve deterministic rounding when storing as an integer 3.425 rounds to 3; 3.531 rounds to 4 the int of 3.425 + 0.5 is 3; the int() of 3.531 + 0.5 = 4.031 is 4. Since bitcoin amounts on the network can only have accuracy down to satoshis, you may have to do rounding on maths which would have a sub-satoshi remainder. An imaginary example would be an exchange that pays you the average price of three other exchanges. (a+b+c)/3 * (1/dollars) may be an irrational result like 166.66666666666666; what the exchange pays in BTC should round up to 166.66666667 if they are fair. |