about palindrome number check

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Nguyen Huy
Nguyen Huy 2021-5-14
编辑： Jan 2021-5-15
%i have number n and i want to check whether that is palindrome
%but the n is too big so i cant use this code,what should i do
%example n= 1.76536927729736e+16
%my code is
if n==str2num(flip(num2str(n)))
flag=true
else
flag=false
end
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Nguyen Huy
Nguyen Huy 2021-5-14
"That really depends on the number of digits that you need to store, which so far you have not told us".Sry about that,i have number 'n',and i have to sum=n+ reverse(n) until i have palindrome
example: n=347
so sum=347+734=1292, 1292+2921=4213, 4213+3124=7337 then stop,because 7337 is palindrome
so i dont know how many digits the sum will have
Stephen23
Stephen23 2021-5-14
As Jan wrote you could store the digits as CHAR or UINT8, which also makes your palindrome checking easy.

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Jan
Jan 2021-5-14
For numbers up to 2^53 the type double represents the digits exactly. This is 9-0e15. See flintmax.
Your example n=1.76536927729736e+16 exceed this limit. Therefore doubles are not useful fpr your needs. You cannot even store the value exactly in a double. Maybe you need an UINT8 vector containing the digits, or a CHAR vector.
It does not matter, if the value is displayed in the e notation or not, because this can be controlled by the command: format
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Nguyen Huy
Nguyen Huy 2021-5-15
thanks guy,i tríed walter way and success
Jan
Jan 2021-5-15
编辑：Jan 2021-5-15
@Walter Roberson: You are right. Thanks for finding this wrong assumption.
When I type this in the command window:
for k = 1:inf, end
No error occurs. Stopping this with Ctrl-C show a warning:
Warning: FOR loop index is too large. Truncating to 2147483647. % R2009b/32
Warning: FOR loop index is too large. Truncating to 9223372036854775807. % R2009b/64, 2018b
I've deleted my wrong claim. Maybe this failed in Matlab 6.5 and I did not try it again.

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