A useful User-Defined Function (determining whether a natural number contains a specified power of 2)

/*

Name: fun_whesponded

Function: determines whether the selected number is in the given integer.

We can know that any natural number can be split into several 2's power and, for example:

1 = 2 ^ 0

2 = 2 ^ 1

3 = 2 ^ 0 + 2 ^ 1

4 = 2 ^ 2

5 = 2 ^ 0 + 2 ^ 2

6 = 2 ^ 1 + 2 ^ 4

7 = 2 ^ 0 + 2 ^ 1 + 2 ^ 2

8 = 2 ^ 3

9 = 2 ^ 0 + 2 ^ 3

10 = 2 ^ 1 + 2 ^ 3

11 = 2 ^ 0 + 2 ^ 1 + 2 ^ 3

12 = 2 ^ 2 + 2 ^ 3

13 = 2 ^ 0 + 2 ^ 2 + 2 ^ 3

14 = 2 ^ 1 + 2 ^ 2 + 2 ^ 3

15 = 2 ^ 0 + 2 ^ 1 + 2 ^ 2 + 2 ^ 3

16 = 2 ^ 4

17 = 2 ^ 0 + 2 ^ 4



Method for resolving any number to the sum of the power of 2-recursion

Rule:

If 14

Limit 2 ^ 3 <14 <2 ^ 4

There must be 8-2 ^ 3 in limit 14

14-8 = 6

Limit 2 ^ 2 <6 <2 ^ 3

IPv6 must have 4--2 ^ 2

6-4 = 2



Limit 2 = 2

Limit 14 = 2 ^ 3 + 2 ^ 2 + 2 ^ 1

Parameters: @ totalnum

Type: int

@ Specifiednum

Type: int

Steps:

Author: waxdoll Cheung

Date: 2005-03-21

*/

Create Function

DBO. fun_whesponded

(

@ Totalnum int,

@ Specifiednum int

)

Returns bit

Begin

Declare @ varret bit

Declare @ varloop int

Set @ varloop = 0

While (@ totalnum> = cast (Power (2, @ varloop) as INT ))

Set @ varloop = @ varloop + 1

Set @ totalnum = @ totalnum-cast (Power (2, @ varloop-1) as INT)

If (@ varloop = @ specifiednum + 1)

Set @ varret = 1

Else

Begin

If (@ totalnum> = 1)

Return DBO. fun_whesponded (@ totalnum, @ specifiednum)

Else

Set @ varret = 0

End

Return @ varret

End

It can be used in many places to see if you can think of it ......