# Gavin Andresen
# 2011-02-24 02:39:59
# https://bitcointalk.org/index.php?topic=3786.msg53946#msg53946

@s{quotedtext}
@s{quotedtext}
 @p{brk}
Converting from a double-precision float from the JSON library to an int64 bitcoin is: @p{brk}

Code:
int64 nAmount = roundint64(dAmount * COIN);
... which will always do the right thing (COIN is 100000000). @p{par}

int64 to JSON string there are no code changes. @p{par}

GUI string to int64 is a direct conversion, no intermediate double precision. @p{par}

And int64 to GUI string is: @p{brk}

Code:
strprintf("%.08f", double(amount)/double(COIN))
... which also always does the right thing (printf of a floating point number rounds, and there is enough precision in a double the rounding will always be correct). @p{par}

0.1 bitcoins will always become exactly 10000000 base units internally, and 10000000 base units will always be shown as exactly 0.10 (in the GUI) or 0.10000000 (in JSON). @p{par}