How to convert a string (numbers) to number(double) without scientific notation

suppose

x='12344566787665546789988776556';

then

y=str2num(x)

should be as

y=12344566787665546789988776556

class(y) should be double

[Sunil Kunjachan]

Thanks Walter. Here my problem is :- Adding two such huge string of numbers and the result should be as a new string with no decimal points inside

[Stephen23]

@Sunil Kunjachan: we understand what you want to do, and Walter Roberson explained why you cannot use double or int64 for this and also gave you two ways to make it work. What else do you need?

Answer 1

[Walter Roberson]

No, that is not possible.

You can use

sprintf('%.0f', 12344566787665546789988776556)

but the result you will get back will be

12344566787665547646753308672

This reflects the fact that your values require 94 bits to represent exactly, but double can hold a maximum of 53 bits of precision.

Your values are also too large to represent in uint64.

If you need exact integers that large then you will need to use the Symbolic Toolbox, or a package such as John D'Errico's Variable Precision Integers in the File Exchange.

[Walter Roberson]

For the case of adding two long numbers, then you can read the numbers as strings, and break the string up into a series of decimal digits, and then do "long-hand" addition on the two. Start at the last (least significant), add the two, if the result is greater than 10 subtract 10 and carry 1, move on to the next pair, add the two plus the carry, and so on.

[Walter Roberson]

See also my response at https://www.mathworks.com/matlabcentral/answers/13231-how-to-make-matlab-display-full-number-digits#answer_305945