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Weird problem in while loop: What is wrong with the input "48" compared to "47" and "49"????

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magie
magie 2022-10-11
评论： magie 2022-10-11
Hi everyone!
I have a weird problem in a while loop with user input:
Within the while loop, the user is asked for the input of a number to be assigned to the variable insnr:
1113 insnr = '0';
1114 while insnr == '0';
1115 insnr = input('Inselnummer [1 ... 999] ? ');
1116 answer = isempty (insnr);
1117 while answer == 1;
1118 disp('Gebe eine gültige Inselnummer ein [1 ... 999] !!!');
1119 insnr='0';
1120 answer = isempty (insnr);
1121 end
1122 end
The code works fine for any number but the number "48".
Execution when using e.g. with the input "47" is as follows:
line 1113 [insr =’0’ char] --> 1114 --> 1115 insnr=47 [insnr=47 double] --> 1116 [answer=0] --> 1122 --> proceed with code properly at line 1123
A check on the input variable insnr yields:
K>> whos(insnr)
Name Size Bytes Class Attributes
insnr 1x1 8 double
Execution when using "48" is magically as follows:
line 1113 [insr =’0’ char] --> 1114 --> 1115 insnr=47 [insnr=47 double] --> 1116 [answer=0] --> 1122 --> 1115 and keeps on returning to this line until I use a number different from 48, e.g. 49
if I check on the input variable insnr:
K>> whos(insnr)
Name Size Bytes Class Attributes
insnr 1x1 8 double
Hence, it looks o.k.
Any idea what could be the problem here with the number "48" ... maybe a Hitchhiker's Guide to the Galaxy issue???
Thanks in advance.
Best, Magie

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采纳的回答

Matt J
Matt J 2022-10-11
编辑：Matt J 2022-10-11
Ran in:
It's because 48 is the ASCII code for '0'.
double('0')
ans = 48
char(48)
ans = '0'
48=='0'
ans = logical
1
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Matt J
Matt J 2022-10-11
Wow! Thanks a lot. That's the solution.
You're quite welcome, but please Accept-click the answer to indicate so.

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