How do I convert from HEX to DEC numbers larger than 2^52?

The MATLAB function "hex2dec" has a input limit of 2^52, how do you convert numbers larger than 2^52 from HEX to DEC in MATLAB?

Answer 1

[MathWorks Support Team]

If the input is greater than 2^52 but smaller than 2^64, consider one of the two options described in the documentation below::

https://www.mathworks.com/help/matlab/ref/hex2dec.html#f72-104326_sep_mw_8a537ff9-c24e-4f07-8539-a5530fa994f8

If the input is greater than or equal to 2^64, you will need to use the Symbolic Toolbox. Please refer to the following example in the documentation for the full workflow:Convert Hexadecimal and Binary Values to Symbolic Decimal Numbers

Below is a simple example code for the workflow:

>> H='0xffffffffffffffffffffffff';
>> D = str2sym(H)
 
D =
 
79228162514264337593543950335

[Walter Roberson]

No, you only need symbolic toolbox if the numbers are > 2^64-1

Answer 2

[Walter Roberson]

If the number is larger than 2^52 then if it is an integer it needs to be either int64 or uint64.

H = '400921fb54442d18';
D = sscanf(H, '%lx')

D = uint64 4614256656552045848

dec2hex(D)

ans = '400921FB54442D18'

num2hex(pi)

ans = '400921fb54442d18'

Dd = typecast(D, 'double')

Dd = 3.1416

Dd - pi

ans = 0

We see we bit-for-bit reconstruction

If the value is intended to be int64 instead of uint64, then use the %lx format to get uint64 and then typecast() that to int64