C++ precision of numbers and truncation with fstream

Question

I have a file.txt with hundreds of numbers. They have many digits (max 20) after the point and I need to get them all without truncation, otherwise they introduce errors in

Answer 1

std::numeric_limits::min std::numeric_limits::digits10 can tell you what your target's actual precision is for long double.

If you find that it's insufficient to represent your data, you probably want arbitrary precision. There are a couple of arbitrary precision number libraries you can use, none of which are standard in C++.

• boost::multiprecision
• GNU MP
• MPFR