C++ – How to calculate the range of data type float in c++

cmathtype conversion

As we can see int has 4 byte in memory, that are 32bits, after applying range formula , we can see range of int -2147483648 to 2147483647. I have calculated the ranges of all datatypes besides float and double and long double.
I dont know how they calculated the range of float mentioned below.

Best Answer

Floating point numbers are stored as an exponent and a fraction within the space available.

For some systems where float is implemented as an IEEE 754 value, the results would looks as below.

sign : 1 bit
exponent : 8 bits
fraction : 23 bits

The exponent allows numbers from 2 ^ (-127) (2 to the power -127) to 2 ^ 128 ( 2 to the power 128).

Allowing a range of numbers from

5.87747E-39 3.40282E+38

the fraction point gives a fraction such as .12313

Thus with 23 bits of values, the accuracy of a number is about 7 decimal digits or 1.19 E-7

For more details see wikipedia : IEEE 754-1985

On a given system, the <cfloat> / <float.h> will give the limits. For non IEEE 754 based representations, you would have to understand how the numbers are stored to calculate the limits.

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C++ – How to iterate over the words of a string

I use this to split string by a delimiter. The first puts the results in a pre-constructed vector, the second returns a new vector.

#include <string>
#include <sstream>
#include <vector>
#include <iterator>

template <typename Out>
void split(const std::string &s, char delim, Out result) {
    std::istringstream iss(s);
    std::string item;
    while (std::getline(iss, item, delim)) {
        *result++ = item;
    }
}

std::vector<std::string> split(const std::string &s, char delim) {
    std::vector<std::string> elems;
    split(s, delim, std::back_inserter(elems));
    return elems;
}

Note that this solution does not skip empty tokens, so the following will find 4 items, one of which is empty:

std::vector<std::string> x = split("one:two::three", ':');

Python – How to check if a string is a number (float)

In case you are looking for parsing (positive, unsigned) integers instead of floats, you can use the isdigit() function for string objects.

>>> a = "03523"
>>> a.isdigit()
True
>>> b = "963spam"
>>> b.isdigit()
False

String Methods - isdigit(): Python2, Python3

There's also something on Unicode strings, which I'm not too familiar with Unicode - Is decimal/decimal

Best Answer

Related Solutions

C++ – How to iterate over the words of a string

Python – How to check if a string is a number (float)

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