Documentation

# bitshift

Shift bits specified number of places

## Syntax

```c = bitshift(a, k) ```

## Description

`c = bitshift(a, k)` returns the value of `a` shifted by `k` bits. The input `fi` object `a` may be a scalar value or a vector and can be any fixed-point numeric type. The output `fi` object `c` has the same numeric type as `a`. `k` must be a scalar value and a MATLAB® built-in numeric type.

The `OverflowAction` property of `a` is obeyed, but the `RoundingMethod` is always `Floor`. If obeying the `RoundingMethod` property of `a` is important, try using the `pow2` function.

When the overflow action is `Saturate` the sign bit is always preserved. The sign bit is also preserved when the overflow action is `Wrap`, and `k` is negative. When the overflow action is `Wrap` and `k` is positive, the sign bit is not preserved.

• When `k` is positive, 0-valued bits are shifted in on the right.

• When `k` is negative, and `a` is unsigned, or a signed and positive `fi` object, 0-valued bits are shifted in on the left.

• When `k` is negative and `a` is a signed and negative `fi` object, 1-valued bits are shifted in on the left.

## Examples

This example highlights how changing the `OverflowAction` property of the `fimath` object can change the results returned by the `bitshift` function. Consider the following signed fixed-point `fi` object with a value of 3, word length 16, and fraction length 0:

`a = fi(3,1,16,0);`
By default, the `OverflowAction` `fimath` property is `Saturate`. When `a` is shifted such that it overflows, it is saturated to the maximum possible value:
```for k=0:16,b=bitshift(a,k);... disp([num2str(k,'%02d'),'. ',bin(b)]);end 00. 0000000000000011 01. 0000000000000110 02. 0000000000001100 03. 0000000000011000 04. 0000000000110000 05. 0000000001100000 06. 0000000011000000 07. 0000000110000000 08. 0000001100000000 09. 0000011000000000 10. 0000110000000000 11. 0001100000000000 12. 0011000000000000 13. 0110000000000000 14. 0111111111111111 15. 0111111111111111 16. 0111111111111111```
Now change `OverflowAction` to `Wrap`. In this case, most significant bits shift off the “top” of `a` until the value is zero:
```a = fi(3,1,16,0,'OverflowAction','Wrap'); for k=0:16,b=bitshift(a,k);... disp([num2str(k,'%02d'),'. ',bin(b)]);end 00. 0000000000000011 01. 0000000000000110 02. 0000000000001100 03. 0000000000011000 04. 0000000000110000 05. 0000000001100000 06. 0000000011000000 07. 0000000110000000 08. 0000001100000000 09. 0000011000000000 10. 0000110000000000 11. 0001100000000000 12. 0011000000000000 13. 0110000000000000 14. 1100000000000000 15. 1000000000000000 16. 0000000000000000```

## Extended Capabilities

### C/C++ Code GenerationGenerate C and C++ code using MATLAB® Coder™. 