Dynamic execution of boolean expression

Hi folks,
I want to execute a boolean expression dynamically, can you pls help me how to do it.
For example,
String str = " ( X & ( Y | Z ) ) " ;
They value of X , Y or Z will be either true or false.
After replacing their value, I will get string as follow
String result = "( true & (false | true ) ".
Now I want to execute the String as boolean expression in order to get
a result as a true or false.
So, i need a solution to implement this. The expression may be simple or compound . It is so urgent waiting for your reply.
Appreciated if you provide sample code.
Thx !
With regards,
Rahul

Java is a compiled language (well, strictly, a semi-compiled language.) This means that stuff like parsing expressions only happens at compile time. Variable names don't exist at run time, neither does the code which analyses expressions.
If you really need to do this kind of thing, therefore, all the code for parsing these expressions has to be a part of your program, and stuff like values for variable names will have to be set explicitly by your program, not in regular variables but in variable list for the "scripting engine" you invoke.
You can either write your own expression analyser (not a trivial task if you haven't done it before) or you can search arround the web for one someone else has written and find out if it covers your requirements. BeenShell has been suggested. Find it on the web and study it's documentation.
Incidentally when the new release of Java comes out it will include serveral such "Scripting engines" for languages like JavaScript or Jython, and such things will be less hastle.

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Dynamic boolean expression evaluation

Hey everyone,
We have a table that consists of a couple key columns and a column containing a boolean expression. We want to select a number of rows based on the key columns and evaluate the boolean expression in the expression column for each, only returning the first row wherein the boolean expression evaluates to true.
We are using a context to inject the test variables into the boolean expressions and currently we are selecting all the key rows in a PL/SQL procedure and going through the cursor evaluating each of the boolean expressions with an execute immediate.
The expressions are currently formated in the columns as anonymous PL/SQL blocks that, when called, will either return true or false to the PL/SQL procedure. Upon returning true, the procedure stops looping and returns true to the caller.
Psuedo-code would be:
- set-up sys_context with condition variables
- create cursor for: select * from expression_tbl et where <key matches>
- begin loop through cursor
- execute immediate cursor_row.expression using out :out_is_true
- if out_is_true = 'Y' then return true
- loop
- return false
The expressions (anonymous PL/SQL blocks) from the table look something like this:
begin if ((''||sys_context('ctx', '1')||'' = 'FL') AND (''||sys_context('ctx', '3')||'' BETWEEN 1619 AND 4598) ) then :1 := 'Y'; end if; end;
This works, but it seems like I should be able to do this another way and potentially extract more performance.
So...a couple questions:
1) I have read on ask Tom that a dynamic select statement (rather than an anonymous PL/SQL block) can evaulate the boolean expressions. I.E. rather than use an execute immediate clause on an anonymous PL/SQL block contained in the expression column, I would make the expression column compatible with a where clause and create this dynamic SQL query: 'select count(*) from dual where ' || expression. I would then execute that query and if it returns a row then the expression is true, otherwise it is false. My question is, does anyone think the performance of parsing the SQL and executing it would be better than that of executing an anonymous PL/SQL block for every row? Tom said that the SQL could incur a lot of hard-parses and kill performance, but how deathly is the constant compilation of anonymous PL/SQL blocks as shown above in comparison?
2) Would there be any benefit to pulling the execute routines out of the PL/SQL block and issuing a query such as the following:
select * from expression_tbl et where <key matches> AND pkg.eval_routine(et.expression) = 'Y' AND rownum <= 1.
I realize that the evaulating routine would then need to either perform an execute immediate on et.expression (if we keep the current method in place) or formulate the dynamic SQL statement and execute it. But, could this be faster than doing the same loop through rows explicitely in PL/SQL?
Doing this would trim my PL/SQL down to:
- set up sys_context
- execute the above select statmenet
- if a row is returned then return true otherwise return false
Seems more elegant, but the peformance is all that matters.
3) Is there any built-in routine that I may be able to replace pkg.eval_routine from 2 with that would evaulate boolean expressions for me? Or any other way to inline the idea from 1 with 2? I can't think of one given the dynamic nature of the beast, but...maybe there's something I missed.
Thanks everyone! Hopefully I've expressed myself clearly.

Brian - According to Tom Kyte Doing PL/SQL inside Execute Immediate should be faster as you are already within the context of a PL/SQL engine. If we choose to do it in SQL then the PL/SQL engine has to hand it over to the SQL Engine for executing the dynamic Select statements and so might be a little slower. But I am not sure if the difference can be quantifiable unless u do your own test of both evaluators and run them for like a few thousand times in a loop.
If you are using 10g R2 - you might want to look into DBMS_RLMGR package which is the API for the Oracle's version of the embedded business rule manager.
I looked into it but it didn't fit our needs as its deficient with respect to rule versioning and effective and until date based business rule enforcement/ validation.
After taking a shot at designing something home grown I feel its not that difficult to construct one that fit our needs inclusive of the features( rule versioning, effective and until dates) that I listed above as deficiencies in the Oracle embedded rule engine.
If you don't have those requirements may be using the Business Rule manager API of 10g R2 might not be a bad anticipating it will be improved in future versions.
Regards
-Suren

Evaluating boolean expressions from a string

Hi All,
In my program I am dynamically generating boolean expressions.
Hence, I store the expression as a string. I want to be able to determine if that expression evaluates to true/false.
For eg, String expr = "1 < 2";
I want to be able to evaluate expr and print false(in this case)
How can I do that? Are there any class that come with JDK1.4 for doing this or can you point me to some API that I can use for this.
Thanks,
Vijay

I can't count how many times this has been askedhere.
Try searching the forums.Give yourself credit - you could count it if you
wanted to.
OK, maybe so. But I can't count it off the top of my
head. :-) But easier than counting the hairs on your head (well.....presuming you do have some....)
Really, it's bizarre how much this gets
asked. I think I'll start a new thread about it...Be realistic....the integer to string or string to integer gets asked a lot more often!

Boolean Expression Evaluator

Hello everyone...
Does any one know how to create a Java program that will evaluate boolean expression... For example, the user may enter (T AND T) OR F statement and the program will check the expression is valid or not and in addition it gives the answer T for true. Does anyone know where to download the free sample code that will be able to help me.. thanks.
URGENT!
-Eugene-

http://www.japisoft.com/formula
Features :
* Decimal, string, boolean operators (or, and, not, xor...)
* Unicode
* Boolean expression support : (A or B) and not ( C equals D )
* String expression support : "abc" != "cba"
* IF THEN ELSE expression
* Short expression format : 2x+3y
* Variable : A=(cos(PI + x )*2) + [y-x]^2
* Multiple lines expression : A = 1 B = A + 1 ...
* Functions with decimal, boolean or string arguments
* Evaluation tree produced by a pluggable parsing system
* Evaluation optimization for symbol value changes
* Standard library with 24 mathematical functions
* Delegate for resolving unknown functions or symbols
* Extend or add a new library dynamically
* Share multiple formula context
* Override any functions from the current library by your one
* Support for multithreaded computing
* Many samples (library extension, graphes) for API interesting parts
* JDK 1.1 compliant (tested on JDK1.1.8 and JDK1.4.2)
Best regards,
A.Brillant

Boolean Expression for get date

Hi Experts,
I am working boolean expression in ssis package. I want download files from ftp and the file name is mic_20141101-mi.txt.
I want to take yesterday files for that i am using expression but i want to give dynamic date which i want give in variable the specific date to download those files from FTP.
For this process i am using Boolean Expression if i give the specific date in variable then its download specific date files from ftp or else its download yesterday files.
Pls help to me for this scenario.
Raj.

You need to have a variable inside SSIS through which you pass the date value
Once passed you can have a script task inside your package to check for the pattern of date variable value inside your file to select correct files
see this for similar logic where i'm looking for files from current day
http://visakhm.blogspot.in/2012/05/package-to-implement-daily-processing.html
Please Mark This As Answer if it solved your issue
Please Mark This As Helpful if it helps to solve your issue
Visakh
My MSDN Page
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Can i use Boolean Expressions in Mail Rules?

Can i use Boolean Expressions in Mail Rules?
I need to create a rule to check whether a message contains BOTH a first and last name of EITHER of two people.
For example, the rule im looking to create goes something like this:
If ANY of the following conditions are met:
message content - contains - john & doe
message content - contains - jane & doe
ive tried and cant seem to get it to work...
Message was edited by: mysterioso

AFAIK Mail rules do not support boolean expressions.
to do what you want you'd have to create two rules
rule 1
if ALL of the following conditions are met
message content - contains - john
message content - contains - jdoe
and similarly for rule 2.

Search problems : Boolean expressions and spam folder

I get about 1000 spam per day that I have to check.
Some of them contains certain keyword that the real emails would never have.
I would like to setup a smart folder or similar that found all emails in the spam folder that contains any of those keywords. I read some blogs etc. that said that spotlight boolean expressions could be used but they do not seem to work.
e.g. "pill OR berry" yields no results at all but when each of the keywords are used on their own they produce 80 or so results each.
Another problem I have is that I can do a manual search in the spam folder by typing in the search field and it yields results. But if I save that as a smart folder it yields no results at all. It seems that the rules do not work on the spam folder.
I then tried to do all this from spotlight in the finder. I found the folder where the spam mailbox emails are stored (called "messages"). I managed to construct a nice search query and save it as a search. But if I delete one of the emails from the finder it still remains in Mail and the next time I start Mail it will be regenerated from somewhere.
Anyone have any insights to provide here?

I had actually missed that preference. Unfortunately it did not help.
Even if I make a new smart mailbox with just one rule (the email must be in the spam folder) it doesnt work. It doesn't matter if I change between any/all either.
I started experimenting with adding a rule saying that the email must not be in any of the other mailboxes but spam. That seemed to work for a bit but as I added more rules, excluding more mailboxes, it eventually broke. I will investigate it a bit more but currently don't have high hopes...

How to convert a boolean expression into a number in SQL (not PL/SQL)

I have a boolean expression
FIELD IN (SELECT FIELD FROM TABLE)
which I would like to convert into a number, preferably into 0 for true and into 1 for false. The reason being that I want to sum the values in a HAVING clause.
I have tried with DECODE, SIGN, TO_NUMBER, but all fail with an error message to the order of wrong type of argument.
Does anyone have an idea?
/poul-jorgen

Hi, you can do it with case if you have Oracle 9i
Regards
Laurent
select case when dummy in ('X') then 1 else 0 end from dual;

Pl/sql boolean expression short circuit behavior and the 10g optimizer

Oracle documents that a PL/SQL IF condition such as
IF p OR q
will always short circuit if p is TRUE. The documents confirm that this is also true for CASE and for COALESCE and DECODE (although DECODE is not available in PL/SQL).
Charles Wetherell, in his paper "Freedom, Order and PL/SQL Optimization," (available on OTN) says that "For most operators, operands may be evaluated in any order. There are some operators (OR, AND, IN, CASE, and so on) which enforce some order of evaluation on their operands."
My questions:
(1) In his list of "operators that enforce some order of evaluation," what does "and so on" include?
(2) Is short circuit evaluation ALWAYS used with Boolean expressions in PL/SQL, even when they the expression is outside one of these statements? For example:
boolvariable := p OR q;
Or:
CALL foo(p or q);

This is a very interesting paper. To attempt to answer your questions:-
1) I suppose BETWEEN would be included in the "and so on" list.
2) I've tried to come up with a reasonably simple means of investigating this below. What I'm attempting to do it to run a series of evaluations and record everything that is evaluated. To do this, I have a simple package (PKG) that has two functions (F1 and F2), both returning a constant (0 and 1, respectively). These functions are "naughty" in that they write the fact they have been called to a table (T). First the simple code.
SQL> CREATE TABLE t( c1 VARCHAR2(30), c2 VARCHAR2(30) );
Table created.
SQL>
SQL> CREATE OR REPLACE PACKAGE pkg AS
2     FUNCTION f1( p IN VARCHAR2 ) RETURN NUMBER;
3     FUNCTION f2( p IN VARCHAR2 ) RETURN NUMBER;
4 END pkg;
5 /
Package created.
SQL>
SQL> CREATE OR REPLACE PACKAGE BODY pkg AS
2
3     PROCEDURE ins( p1 IN VARCHAR2, p2 IN VARCHAR2 ) IS
4        PRAGMA autonomous_transaction;
5     BEGIN
6        INSERT INTO t( c1, c2 ) VALUES( p1, p2 );
7        COMMIT;
8     END ins;
9
10     FUNCTION f1( p IN VARCHAR2 ) RETURN NUMBER IS
11     BEGIN
12        ins( p, 'F1' );
13        RETURN 0;
14     END f1;
15
16     FUNCTION f2( p IN VARCHAR2 ) RETURN NUMBER IS
17     BEGIN
18        ins( p, 'F2' );
19        RETURN 1;
20     END f2;
21
22 END pkg;
23 /
Package body created.Now to demonstrate how CASE and COALESCE short-circuits further evaluations whereas NVL doesn't, we can run a simple SQL statement and look at what we recorded in T after.
SQL> SELECT SUM(
2           CASE
3              WHEN pkg.f1('CASE') = 0
4              OR   pkg.f2('CASE') = 1
5              THEN 0
6              ELSE 1
7           END
8           ) AS just_a_number_1
9 ,      SUM(
10           NVL( pkg.f1('NVL'), pkg.f2('NVL') )
11           ) AS just_a_number_2
12 ,      SUM(
13           COALESCE(
14             pkg.f1('COALESCE'),
15             pkg.f2('COALESCE'))
16           ) AS just_a_number_3
17 FROM    user_objects;
JUST_A_NUMBER_1 JUST_A_NUMBER_2 JUST_A_NUMBER_3
              0               0               0
SQL>
SQL> SELECT c1, c2, count(*)
2 FROM   t
3 GROUP BY
4         c1, c2;
C1                             C2                               COUNT(*)
NVL                            F1                                     41
NVL                            F2                                     41
CASE                           F1                                     41
COALESCE                       F1                                     41We can see that NVL executes both functions even though the first parameter (F1) is never NULL. To see what happens in PL/SQL, I set up the following procedure. In 100 iterations of a loop, this will test both of your queries ( 1) IF ..OR.. and 2) bool := (... OR ...) ).
SQL> CREATE OR REPLACE PROCEDURE bool_order ( rc OUT SYS_REFCURSOR ) AS
2
3     PROCEDURE take_a_bool( b IN BOOLEAN ) IS
4     BEGIN
5        NULL;
6     END take_a_bool;
7
8 BEGIN
9
10     FOR i IN 1 .. 100 LOOP
11
12        IF pkg.f1('ANON_LOOP') = 0
13        OR pkg.f2('ANON_LOOP') = 1
14        THEN
15           take_a_bool(
16              pkg.f1('TAKE_A_BOOL') = 0 OR pkg.f2('TAKE_A_BOOL') = 1
17              );
18        END IF;
19
20     END LOOP;
21
22     OPEN rc FOR SELECT c1, c2, COUNT(*) AS c3
23                 FROM   t
24                 GROUP BY
25                        c1, c2;
26
27 END bool_order;
28 /
Procedure created.Now to test it...
SQL> TRUNCATE TABLE t;
Table truncated.
SQL>
SQL> var rc refcursor;
SQL> set autoprint on
SQL>
SQL> exec bool_order(:rc);
PL/SQL procedure successfully completed.
C1                             C2                                     C3
ANON_LOOP                      F1                                    100
TAKE_A_BOOL                    F1                                    100
SQL> ALTER SESSION SET PLSQL_OPTIMIZE_LEVEL=0;
Session altered.
SQL> exec bool_order(:rc);
PL/SQL procedure successfully completed.
C1                             C2                                     C3
ANON_LOOP                      F1                                    200
TAKE_A_BOOL                    F1                                    200The above shows that the short-circuiting occurs as documented, under the maximum and minimum optimisation levels ( 10g-specific ). The F2 function is never called. What we have NOT seen, however, is PL/SQL exploiting the freedom to re-order these expressions, presumably because on such a simple example, there is no clear benefit to doing so. And I can verify that switching the order of the calls to F1 and F2 around yields the results in favour of F2 as expected.
Regards
Adrian

Search MessageSelector sample for complex boolean express with AND, OR, NOT

As far as I know I can specify in the "Message Selector" field of a JMS-PartnerLink
a boolean expression.
How are AND, OR and NOT written here? Can I use brackets?
Can I use blanks inside the boolean expression?
Assume I would like to specify:
((myfield1 > 3.0) && (myfield2 == 777)) || (myfield3 != 'aaa')
Is the syntax correct for this?

http://www.mcs.csueastbay.edu/support/oracle/doc/10.2/server.102/b14257/jm_create.htm
11.3 JMS Point-to-Point Model Features/MessageSelector
that will give you some examples of how to use it

Short-circuiting boolean expressions

There is a term used in other languages to describe the behavior of compiled code which evaluates boolean expressions: short circuiting. Basically, it means that if a term in an expression determines its value, then following terms never get evaluated, since they are irrelevant. For example, I have noticed that this always works in AppleScript:
if class of x is not integer or x > 32 then . . . .
But this will throw an exception if x is something that can’t be coerced into a number:
if x > 32 or class of x is not integer then . . . .
It looks to me that the reason the first always works is that Applescript is short-circuiting, and therefore there is no attempt to evaluate the inequality if x is of inappropriate class.
Does anyone know if Applescript’s behavior is sufficiently well defined that I can be confident it will always short circuit? I know I can avoid the issue by breaking such expressions into separate, nested, if statements. If there is no such assurance that is what I will probably make a habit of doing. But I thought I'd ask if this is really necessary.

Hello
Short-circuiting is well-defined in AppleScript.
cf. ASLG > Operator References (p.179 of ASLG pdf)
http://developer.apple.com/library/mac/documentation/AppleScript/Conceptual/Appl eScriptLangGuide/AppleScriptLanguageGuide.pdf
Regards,
H

Error in boolean expression

I try to enter a formula in an field for hiding the output on certain conditions
I enter IF(@i_report_type == 'P',true,false)
but I get the error that a boolean expression/value is required ????
I don't know what is wrong with true and false as boolean ?
if I put it in capitals then I get the error unrecoginezed identifier 'True' ??
do I miss some strange logic here ??
kind regards
arthur

Hi Arthur,
you might want to try the following:
BOOL(IF(@i_report_type == 'P',true,false))
Hope this helps.
Regards,
Joseph

Create and save boolean expressions for later evaluation

Is it possible to create Boolean expressions by inputs via user interface in LabVIEW and save them for later evaluation? I am interested in creating a 'flexible policy engine' which involves creating 'rules' comprising attribute values of certain attributes of objects based on boolean expressions which can later be used for arriving at some decisions based on the 'rules'.

Hi Belur,
Have you considered building a script based on the boolean expressions that you want to create for the flexible policy and saving the script to file?
Later, you can read the script and depending on the policy, it can re-create the boolean expressions.
A simple way to implement this is by having various pre-defined expressions places into a Case Statement. The script calls the appropriate cases that create the complete expression.
You can store the attributes of the objects and when the vi is running, it can first open the initialization file, read the attributes and set them.
For instance, you can read from and write to Property (and Invoke Nodes) to which you can the attributes.
Unfortunately, I don't have an example of this that I c
an share with you. There may be some if you do a search.
Hope this helps..
JLV

Taking out IF's and returning a boolean expression

I thought a better way to implement this later method might be to remove the IF's and just return a boolean expression true or false if one date object is later than another date object. I almost have it correct but one case is still not outputting correctly.
Heres the return statement:
return ((year > otherDate.year)||(year==otherDate.year)&&(month > otherDate.month)&&
(day > otherDate.day));

someone told you that the code looked right? humm... don't look right to me.
basically if the years are different you are done and know the answer but if the years are the same you must look to the month
So why don't you have exactly the same situation to deal with the case where you only look at the day if the months are equal? You need an extra set of parens, and another || condition and a term involving == months.
Nope, your code just mixes together the code for checking days and checking months.
You CAN do this all in a single boolean expression, but it is nested two levels deep and too long to fit on a line. And you got it wrong. (this is a hint that the person reading the code will also not be sure that the code is correct)
You have done no one a favor by removing the IFs and using a single complicated boolean expression.

Boolean expression for calculation problem

Hi experts,
I have following Keyfigures arranged in my Report:
A | B | AB | C | D | CD
*A,B,C,D are key figures in column
Now the user has demanded that they want to see only positive numbers in that Report and add all negative numbers in one column
Desired:
A (Only More than 0) | B (Only More than 0) | AB | C (Only More than 0) | D (Only more than 0) | CD | ABC+D(where A,B,C,D are less than 0) * -1
I know I have to do it using formula and boolean expression but dont know how.

Create new Calculated KFs using Boolean operators and hide original KFs.
(A > 0) * A
(B > 0) *B ....
Similarly others
((ABCD) <0)*(ABCD) for -ve values
Jaya

Dynamic execution of boolean expression

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