boolean-logic

Lets say I have a table of articles with as many to many relationship with topics. Each topic assigned to an article has a type field which can contain 1 of 3 values AND , NOT , and OR . Articles id .... Topics id .... ArticleTopics article_id topic_id type I want to create a query that says returns all articles that have: ALL of the following topics: 1, 2, 3 (AND association) AND ANY of the following topics: 4, 5, 6 (OR association) AND NONE of the following topics 7, 8 (NOT association) How do I go about creating this query? Thanks in advance! The ALL and NOT parts are very simple, you just

I'm trying to build a simple Prolog SAT solver. My idea is that the user should enter the boolean formula to be solved in CNF (Conjuctive Normal Form) using Prolog lists, for example (A or B) and (B or C) should be presented as sat([[A, B], [B, C]]) and Prolog procedes to find the values for A, B, C. My following code is not working and I'm not understanding why. On this line of the trace Call: (7) sat([[true, true]]) ? I was expecting start_solve_clause([_G609, _G612]]) . Disclaimer: Sorry for the crappy code I didn't even know about Prolog or the SAT problem a few days ago. P.S.: Advice on

In a browser console, entering 1===1 evaluates to true . Entering 1===1===1 evaluates to false . I assume that this is because of the way the statement is evaluated: 1 === 1 === 1 becomes (1 === 1) === 1 which evaluates to true === 1 which is false . Is this correct? If not, what's the real reason for this behaviour? Yes, you're exactly right. Here you have two equality checks, which have the same operator precedence. First one evaluates first, then its result applies to the next equality check. 1===1===1 is the same as (1===1)===1 which is true===1 which is false , because here you check by

I'm looking to write a Truth Table Generator as a personal project. There are several web-based online ones here and here . (Example screenshot of an existing Truth Table Generator ) I have the following questions: How should I go about parsing expressions like: ((P => Q) & (Q => R)) => (P => R) Should I use a parser generator like ANTLr or YACC, or use straight regular expressions? Once I have the expression parsed, how should I go about generating the truth table? Each section of the expression needs to be divided up into its smallest components and re-built from the left side of the table

Possible Duplicate: Is it bad to explicitly compare against boolean constants e.g. if (b == false) in Java? In this NotePadProvider sample code , I noticed that the author chose the form: if (values.containsKey(NoteColumns.CREATED_DATE) == false) { values.put(NoteColumns.CREATED_DATE, now); } Over: if (!values.containsKey(NoteColumns.CREATED_DATE)) { values.put(NoteColumns.CREATED_DATE, now); } Is there any advantage in the first form over the more logical one? Apart from "readability", no. They're functionally equivalent. ("Readability" is in quotes because I hate == false and find ! much

Currently I have a web application where a user can use dropdown lists to generate SQL SELECT statements like so: Column Select Dropdown | Operator Dropdown (= != > < <= >=) | Value select dropdown The user can do this multiple times, and the "filters" are currently all ANDed together. I want to add the possibility of creating OR statements. I could very easily add ORs in the case where the columns are the same, but what about complex logic statements like ((A OR B OR C) AND (D OR E)) OR (F AND G)? How can I let users create such statements in a user-friendly way? EDIT: To specify, user

In JavaScript, it seems: (4294958077 | 0) == -9219 Why is it not 4294958077 ? It suggests that there's some sort of overflow kicking in (although as I understand it a JavaScript Number type's range is +/- 9007199254740992 so that's odd in itself.) Even if it was an overflow, surely (4294958077 | 0) == 4294958077 should evaluate as true - but it doesn't. Help please It has nothing to do with floating point type or overflows. It returns -9219 because the standard mandates it, as all binary bitwise operations have to be done using signed 32-bit integers (ECMA-262 §11.10). The production A : A @ B

So it ended up that the bug that had kept me on for days, was a section of code that should have evaluated to False evaluating to True. My initial code went something like: if(~x && ~y) begin //do stuff end i.e. If x is NOT ONE and y is NOT ONE then do stuff. Stepping through the debugger, I realized even though x was 1 the expression in the if-statement still resulted into TRUE and the subsequent code was executed. However, when I changed the statement to: if(x == 0 && y == 0) begin //do stuff end and also tried: if(!x && !y) begin //do stuff end the code within the if-statement was not

On the Wikipedia page for SQL there are some truth tables about boolean logic in SQL. [1] The Wikipedia page seems to source the SQL:2003 standard. The truth table for the equals operator (=) is different from the IS operator from the SQL:2003 draft. Also, the Wikipedia article notes that "IS NULL" (<null predicate>) is a special case. In the SQL:2003 it seems that there is an "IS" opeartor which is a regular operator like AND, NOT and OR. However, the <null predicate> is still there. Why is the <null predicate> there when the IS is a regular boolean operator? Is it to make sure you can use