Print a float number in normal form, not exponential form / scientific notation [duplicate]
You can format it as a fixed-point number. >>> a = 1/1221759 >>> ‘{0:.10f}’.format(a) ‘0.0000008185’
floating-point
Does the C++ standard specify anything on the representation of floating point numbers?
From N3337: [basic.fundamental/8]: There are three floating point types: float, double, and long double. The type double provides at least as much precision as float, and the type long double provides at least as much precision as double. The set of values of the type float is a subset of the set of values of … Read more
std::stod throws out_of_range error for a string that should be valid
Converting “7.63918e-313” The C++ standard allows conversions of strings to double to report underflow if the result is in the subnormal range even though it is representable. 7.63918•10-313 is within the range of double, but it is in the subnormal range. The C++ standard says stod calls strtod and then defers to the C standard … Read more
C dynamically printf double, no loss of precision and no trailing zeroes
There’s probably no easier way. It’s a quite involved problem. Your code isn’t solving it right for several reasons: Most practical implementations of floating-point arithmetic aren’t decimal, they are binary. So, when you multiply a floating-point number by 10 or divide it by 10, you may lose precision (this depends on the number). Even though … Read more
Golang converting float64 to int error
You need to understand something: 100.55 is a decimal number (presented in decimal radix). 100.55 in decimal is a finite number and is exactly this: 100.55. Computers in general store numbers in binary representation. The number 100.55 cannot be represented with a finite binary number: 100.55 is an infinite number in binary representation (same reason … Read more
Maximum number of decimal digits that can affect a double
When you have a subnormal number with odd significand, that is, an odd multiple of 2^(-1074), you have a number whose last nonzero digit in the decimal representation is the 1074th after the decimal point. You then have around 300 zeros directly following the decimal point, so the number has around 750-770 significant decimal digits. … Read more
Rounding to n significant digits
To round to d significant digits: >> d = 3; %// number of digits >> x = 5.237234; %// example number >> D = 10^(d-ceil(log10(x))); >> y = round(x*D)/D y = 5.2400 To round to d decimal digits: >> d = 3; %// number of digits >> x = 5.237234; %// example number >> D … Read more
C fundamentals: double variable not equal to double expression?
I suspect you’re using 32-bit x86, the only common architecture subject to excess precision. In C, expressions of type float and double are actually evaluated as float_t or double_t, whose relationships to float and double are reflected in the FLT_EVAL_METHOD macro. In the case of x86, both are defined as long double because the fpu … Read more
on what systems does Python not use IEEE-754 double precision floats
Update: Since I wrote the original answer below, the situation has changed slightly. CPython versions 3.11 and later now require that the platform C double follows the IEEE 754 binary64 format. This was mostly a matter of convenience for developers – it allowed us to remove special-case code that was in practice close to untestable. … Read more
Conditional tests in primality by trial division
UPD: This is a compiler optimization issue, obviously. While MinGW used only one div instruction in loop body, both GCC on Linux and MSVC failed to reuse the quotient from previous iteration. I think the best we could do is explicitly define quo and rem and calculate them in the same basic instruction block, to … Read more