why the subtraction gives the wrong ans.?

12 次查看（过去 30 天）
Sultan Mehmood
Sultan Mehmood 2019-7-16
回答： Kiran Kintali 2023-2-7
y=uint16(22);
>> Z=uint16(164);
>> S=y-Z
S =
0
how i get an ans = -142
  2 个评论
KSSV
KSSV 2019-7-16
You are asking same question repeatedly........
Shashank Sharma
Shashank Sharma 2019-7-16
编辑：Shashank Sharma 2019-7-16
You are using uint all such integers are unsigned.
You cannot store negative numbers in a uint type.

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回答（3 个）

Shashank Sharma
Shashank Sharma 2019-7-16
If you want to store negative it is better to convert it to int16.
This makes it possible to store negative integers.
The format is Y = int16(X);
Walter Roberson
Walter Roberson 2019-7-16
double(y) - double(Z)
You could also get away with
int32(y) - int32(Z)
However, int16(y) - int16(Z) will not work reliably: it will have problems if any of the entries exceed 32767.
Kiran Kintali
Kiran Kintali 2023-2-7
Integers in MATLAB have Saturation behaviors.
To avoid saturation behavior of Integers when using MATLAB Code, you may need to consider the following code generation options or consider using fixed-point math for finer control on the numerics.
By default (and when the "Saturation on integer overflow" is checked in MATLAB coder settings), when an arithmetic operation involving integers exceeds the maximum or minimum value, the result is set to the maximum or minimum value. This is known as "saturation"
For example, if we consider 8-bit signed integers with a maximum value of 127 and a minimum value of -128:
>> x = int8(127) + 1
x =
int8
127
>> x = int8(-128) - 1
x =
int8
-128
>> x = int8(-128) - 8
x =
int8
-128
When the "Saturation on integer overflow" property is unchecked, then any amount that overflows or exceeds the maximum or minimum value is wrapped around to the opposite extreme. This is known as "wrapping". For example:
>> x = int8(127) + 1
x =
int8
-128
>> x = int8(-128) - 1
x =
int8
127
>> x = int8(-128) - 8
x =
int8
120
Please note that this checkbox applies only to MATLAB code generation, and not to executing MATLAB files or executing MATLAB commands in the Command Window. For more information regarding this behavior, see the following documentation:
https://www.mathworks.com/help/fixedpoint/range.html?s_tid=CRUX_lftnav

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