Digvijoy Chatterjee schrieb:

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... here is a simple program, int main() { double d=76.32; std::string s = boost::lexical_caststd::string(d); cout << s << endl; }

output 76.319999999...

a) am i doing something wrong ??

I don't think so.

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b) if this is not wrong s this standard behavior ??

I'd say so. Due to the binary representation not all numbers with a representation of a fixed amount of digits in our decimal system have such a representation in the computer. Lexical_cast internally uses standard streams, if they don't correct such things (and I don't know of any implemementation that'd do so), your output will look garbaged. Try adding std::cout << d << std::endl.

adding std::cout << d << std::endl; does prints it out correctly, it calls setprecision with a default value of 6 which does rounding , I assume there is no way to play with setprecision and lexical_cast , or to a more general problem of rounding doubles to certain places of decimals while converting them to strings, as u say

not all numbers with a representation of a fixed amount of digits in our decimal system have such a representation in the computer.

I switched to ostringstream ,which does the job for the moment, because of setprecision (6) but the code now is not as succinct as lexical_cast. Thx Digz