【叶子函数分享十七】中缀算术转后缀算术表达式并计算的函数
--创建函数(原创：cson_cson)
create function dbo.js(@bds varchar(1000))
returns float
as
begin
declare @i int,@j int
declare @c1 char(1),@c2 char(1),@c varchar(100)
declare @v1 float,@v2 float,@v float
declare @t table(id int identity(1,1),s varchar(100))
declare @s table(id int identity(1,1),s varchar(100))
declare @sv table(id int identity(1,1),v float)
select @i = 0,@j = len(@bds),@c2 = '',@c = ''
while @i<@j
begin
select @c1 = @c2,@i = @i+1
select @c2 = substring(@bds,@i,1)
if charindex(@c2,'.0123456789') > 0 or (@c2 = '-' and @c1 in('','*','-','+','/','('))
begin select @c = @c + @c2 continue end
if @c <> '' begin insert @t(s) select @c select @c = '' end
if charindex(@c2,')')>0
begin
insert @t(s) select s from @s where id > isnull((select max(id) from @s where s in('(')),0) order by id desc
delete @s where id >= isnull((select max(id) from @s where s in('(')),0)
continue
end
if charindex(@c2,'+-)')>0
begin
insert @t(s) select s from @s where id > isnull((select max(id) from @s where s in('(')),0) order by id desc
delete @s where id > isnull((select max(id) from @s where s in('(')),0)
if @c2 <> ')' insert @s(s) select @c2
continue
end
if charindex(@c2,'*/')>0
begin
insert @t(s) select s from @s where id > isnull((select max(id) from @s where s in('(','+','-')),0) order by id desc
delete @s where id > isnull((select max(id) from @s where s in('(','+','-')),0)
insert @s select @c2
continue
end
if charindex(@c2,'(')>0 insert @s select @c2
end
if @c <> '' insert @t(s) select @c
insert @t(s) select s from @s order by id desc
select @i = 0,@j = max(id) from @t
while @i < @j
begin
select @i = @i + 1
select @c = s from @t where id = @i
if @c = '(' continue
if @c not in('*','-','+','/') begin insert @sv(v) select convert(float,@c) continue end
select @v2 = v from @sv delete @sv where id = (select max(id) from @sv)
select @v1 = v from @sv delete @sv where id = (select max(id) from @sv)
select @v = case @c when '+' then @v1 + @v2 when '-' then @v1 - @v2
when '*' then @v1 * @v2 when '/' then @v1 / @v2 end
insert @sv(v) select @v
end
select @v = v from @sv
return @v
end
--测试示例
declare @bds varchar(100)
select @bds = '1+(2+3)*4-9'
select dbo.js(@bds) as func
--运行结果
/*
func
----------------------
12
*/