巧用DataWindwo返回计算表达式的值,该如何处理

巧用DataWindwo返回计算表达式的值
应脚本语言版主sdhylj（ss 婶婶^_^）的要求，整理了下用dw返回计算表达式值的相关文档

1、返回比较表达式如60 < 70的函数

函数f_exp_compare

C/C++ code


//====================================================================
// 函数: f_exp_compare
//--------------------------------
// 描述: 返回比较表达式的结果
//--------------------------------
// 参数:
//     value    string    as_str    表达式，如 60 < 70
//--------------------------------
// 返回值:  string   比较表达试的结果 1为真，0为假，-1为表达式错误
//====================================================================
String ls_Ret
DataStore lds_Evaluate
lds_Evaluate = CREATE DataStore
lds_Evaluate.Create('release 8;~r~ntable()')
ls_Ret = lds_Evaluate.Describe("Evaluate('" + "if(" + as_str + ", 1, 0)" + "', 1)")
DESTROY lds_Evaluate
IF ls_Ret = '!' THEN ls_Ret = '-1'
RETURN ls_Ret

示例：

C/C++ code


String ls_Exp, ls_Ret

ls_Exp = '60 < 70'
ls_Ret = f_exp_compare(ls_Exp)
MessageBox('', ls_Exp + ' --> ' + ls_Ret )

2、返回计算表达式如2 * (3+5) + 2^3的函数

C/C++ code


//====================================================================
// 函数: f_exp_ret
//--------------------------------
// 描述: 返回计算表达式的值
//--------------------------------
// 参数:
//     value    string    as_str    计算表达式，如 2 * (3+5) + 2^3
//--------------------------------
// 返回值:  string   计算表达式的结果值，如果表达式不正确，返回'FALSE'
//====================================================================
String ls_Ret
DataStore lds_Evaluate
lds_Evaluate = CREATE DataStore
lds_Evaluate.Create('release 8;~r~ntable()')
ls_Ret = lds_Evaluate.Describe("Evaluate('" + as_str + "', 1)")
DESTROY lds_Evaluate
IF ls_Ret = '' OR ls_Ret = '!' THEN ls_Ret = 'FALSE'
RETURN ls_Ret

示例：

C/C++ code


String ls_Exp, ls_Ret

ls_Exp = '60 * ( 1 + 3 ) + 2^3'
ls_Ret = f_exp_ret(ls_Exp)
MessageBox('', ls_Exp + ' --> ' + ls_Ret )

3、下面是收藏的在SQL中返回计算表达式的函数，但只能算加、减、乘、除，不能算幂：

SQL code


CREATE FUNCTION dbo.GetExp(@pstrExpress AS VARCHAR(8000))
RETURNS DECIMAL(18,6) AS
BEGIN
DECLARE @i INT,@j INT 
DECLARE @c1 CHAR(1),@c2 CHAR(1),@c VARCHAR(100)
DECLARE @v1 DECIMAL(18,6),@v2 DECIMAL(18,6),@v DECIMAL(18,6)
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 DECIMAL(18,6))

SET @pstrExpress = REPLACE(@pstrExpress,' ','')
SELECT @i = 0,@j = LEN(@pstrExpress),@c2 = '',@c = ''
WHILE @i<@j
BEGIN
 SELECT @c1 = @c2,@i = @i+1
 SELECT @c2 = SUBSTRING(@pstrExpress,@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

巧用DataWindwo返回计算表达式的值,该如何处理

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