Converting hexadecimal to decimal in base 10 using a loop (not function hex2dec)

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Zack Rabas
Zack Rabas 2018-11-12
回答： vamsi krishna 2020-11-8
I am running the following code and it is only working when I plug in either just numbers or just letters, but I cannot get it to work for both. For example, "F4E" will not work, but "FF" or "44" work. Why is this happening?
num = input('Enter a hexidecimal number (e.g. FF):', 's');
y = double(num);
x = 0;
for i = 1:length(num)
if y > 47 & y < 58
y = y - 48;
elseif y > 64 & y < 71
y = y - 55;
elseif y > 96 & y < 103
y = y - 87;
end
x = x + y(i) * 16^(length(num)-i);
end

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回答（3 个）

Walter Roberson
Walter Roberson 2018-11-12
if y > 47 & y < 58
should be indexing y(i)
Guillaume
Guillaume 2018-11-12
For reference, here is how I would implement the conversion efficiently in matlab (without using hex2dec):
hex = upper(input('Enter a hexidecimal number (e.g. FF):', 's'));
lookup = [];
lookup(['0':'9', 'A':'F']) = 0:15; %lookup table to convert character to corresponding decimal value
dec = polyval(lookup(hex), 16); %convert characters to decimal value and multiply by corresponding power of 16
No loop needed.
vamsi krishna
vamsi krishna 2020-11-8
a=input("enter the no. in double quotes ");
A=char(a);
l=strlength(a);
i=1;b=0;
while (l>0)
if ((A(i)>='0')&&(A(i)<='9'))
b=(A(i)-48)+b*16;
elseif ((A(i)>='A')&&(A(i)<='E'))
b=(A(i)-55)+b*16;
end
i=i+1;
l=l-1;
end
fprintf("value of given no. %s in decimal is %d",a,b);

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