From the C++ Standard The type of a floating literal is double unless explicitly specified by a suffix. The suffixes f and F specify float, the suffixes l and L specify long double. It is interesting to compare with corresponding paragraph of the C Standard. In C there is used term floating constant instead of … Read more
These are talking about two slightly different things. The 7.2251 digits is the precision with which a number can be stored internally. For one example, if you did a computation with a double precision number (so you were starting with something like 15 digits of precision), then rounded it to a single precision number, the … Read more
To put it simple, digits10 is the number of decimal digits guaranteed to survive text → float → text round-trip. max_digits10 is the number of decimal digits needed to guarantee correct float → text → float round-trip. There will be exceptions to both but these values give the minimum guarantee. Read the original proposal on … Read more
The reason you’re not getting your exact value of a is that R is storing it as a double instead of as an integer. Because a is very large, there is some rounding that takes place when you assign a. Normally to store things as integers you would use L at the end of the … Read more
pow works with double numbers. These represent numbers of the form s * 2^e where s is a 53 bit integer. Therefore double can store all integers below 2^53, but only some integers above 2^53. In particular, it can only represent even numbers > 2^53, since for e > 0 the value is always a … Read more
Formatting a floating point number is rather non-trivial. Search e.g. for the Dragon4 algorithm (here is one result). Very, very naively, you could try this: Handle NaN and Infinity. Print the sign (check < 0). Assume henceforth the number is positive real. If >= 1, truncate and use familiar integer formatting to print the integral … Read more
You can use setScale() e.g. double d = … BigDecimal db = new BigDecimal(d).setScale(12, BigDecimal.ROUND_HALF_UP);
#include <iostream> #include <stdlib.h> #include <iomanip> int main() { int a = 5; int b = 10; std::cout << std::fixed; std::cout << std::setprecision(4); std::cout << (float)a/(float)b << “\n”; return 0; } You need to pass std::fixed manipulator to cout in order to show trailing zeroes.
Floats are a number representation with a certain precision. Not every value can be represented in this format. See here as well. You can easily think of why this would be the case: there is an unlimited number of number just in the intervall (1..1), but a float only has a limited number of bits … Read more
This really has nothing to do with Python – you’d see the same behavior in any language using your hardware’s binary floating-point arithmetic. First read the docs. After you read that, you’ll better understand that you’re not adding one one-hundredth in your code. This is exactly what you’re adding: >>> from decimal import Decimal >>> … Read more