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ASF GitHub Bot commented on THRIFT-3636: ---------------------------------------- Github user hcorg commented on a diff in the pull request: https://github.com/apache/thrift/pull/870#discussion_r52925705 --- Diff: lib/cpp/src/thrift/protocol/TJSONProtocol.cpp --- @@ -524,7 +524,8 @@ namespace { std::string doubleToString(double d) { std::ostringstream str; str.imbue(std::locale::classic()); - str.precision(std::numeric_limits<double>::digits10 + 1); + // new precision is 17 equal to max_digits10(c++11) or digits10+2 + str.precision(17); --- End diff -- IMHO `const double max_digits10 = 2 + std::numeric_limits<double>::digits10;` `str.precision(max_digits10);` looks better than comment ;) I'd even consider naming variable `max_digits10_cpp11` > The precision is 15 bits after dot of casting from double to string in > Thrift-cpp-library- json-protocol. > --------------------------------------------------------------------------------------------------------- > > Key: THRIFT-3636 > URL: https://issues.apache.org/jira/browse/THRIFT-3636 > Project: Thrift > Issue Type: Bug > Components: C++ - Library > Affects Versions: 0.9.3 > Environment: Linux Mac Windows > Reporter: WangYaofu > Assignee: WangYaofu > Fix For: 0.9.4 > > > The precision is 15 bits after dot of format casting from double to string in > Thrift-cpp-library- json-protocol. > But the expected precision is 16 bits after dot in Thrift-json-protocol. > The solution: > To Change code 'str.precision(std::numeric_limits<double>::digits10 + 1);' to > 'str.precision(std::numeric_limits<double>::digits10 + 2);' > in function doubeToString file TJSONProtocol.cpp at line 524, > e.g: > before: > In C++ TJsonProtocol.cpp: > double a = 1.12345678906666663; > string astr = doubleToString(a); > double b = stringToDouble(astr); > the result as below: > a = 1.1234567890666667 > astr = "1.123456789066667" > b = 1.1234567890666669 > after changing: > the result as below: > a = 1.1234567890666667 > astr = "1.1234567890666667" > b = 1.1234567890666667 > This result is expected. -- This message was sent by Atlassian JIRA (v6.3.4#6332)