-- =============================================

-- Author:      <maco_wang>

-- Create date: <2011-03-22>

-- Description: <SQL位移运算函数>

-- =============================================

go

--创建函数

create function displacement(@n as bigint,@m as varchar(3))

returns int

as

begin

    declare @maco varchar(50);set @maco=''

    declare @i int

    declare @x int

    declare @s int

    while (@n<>0)

    begin

       set @maco=@maco+convert(char(1),@n%2)

       set @n=@n/2

    end

    set @maco=reverse(@maco)

    set @maco=RIGHT('0000'+@maco,4)

    set @s=LEN(@maco)

    set @i=convert(int,RIGHT(@m,1))

    set @x=1

    if LEFT(@m,2)='<<'

    begin

      while(@x<=@i)

      begin

       select @maco=@maco+'0'

       select @x=@x+1

      end

      select @maco=RIGHT(@maco,@s)

    end

    if LEFT(@m,2)='>>'

    begin

      while(@x<=@i)

      begin

       select @maco='0'+@maco

       select @x=@x+1

      end

      select @maco=LEFT(@maco,@s)

    end

    set @i=LEN(@maco)

    set @s=0

    while(@i>0)

    begin

      if SUBSTRING(@maco,LEN(@maco)-@i+1,1)='1'

      begin

       select @s=@s+POWER(2,convert(float,@i-1))

      end

      select @i=@i-1

    end

    return @s

end

 

--测试示例

select dbo.displacement(1,'<<3') 

select dbo.displacement(8,'>>1')

select dbo.displacement(12,'>>3')

 

--运行结果

/*

8

4

1

*/