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Posted to commits@doris.apache.org by GitBox <gi...@apache.org> on 2019/11/27 08:30:40 UTC
[GitHub] [incubator-doris] marising edited a comment on issue #2274: Support
more column type change
marising edited a comment on issue #2274: Support more column type change
URL: https://github.com/apache/incubator-doris/issues/2274#issuecomment-558981844
http://www.softelectro.ru/ieee754_en.html
According to the definition of IEEE754, the effect of converting a float binary to a double binary is the same as that of static_cast <double>. Data precision cannot be guaranteed, but the progress of decimal system can be guaranteed by converting a float binary to a char buffer and then to a double.
==System==
float 0.3000000 is: 0 | 01111101 | 00110011001100110011010
double 0.300000000000000 is: 0 | 01111111101 | 0011001100110011001100110011001100110011001100110011
==Convert Binary==
float 0.3000000 is: 0 | 01111101 | 00110011001100110011010
double 0.300000011920929 is: 0 | 01111111101 | 0000000000000000000001000000000000000000000000000000
==float to char to strtod==
float 0.3000000 is: 0 | 01111101 | 00110011001100110011010
double 0.300000000000000 is: 0 | 01111111101 | 0011001100110011001100110011001100110011001100110011
==static cast==
float 0.3000000 is: 0 | 01111101 | 00110011001100110011010
double 0.300000011920929 is: 0 | 01111111101 | 0000000000000000000001000000000000000000000000000000
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