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  • Lazy Evaluation in Bash

    - by User1
    Is there more elegant way of doing lazy evaluation than the following: pattern='$x and $y' x=1 y=2 eval "echo $pattern" results: 1 and 2 It works but eval "echo ..." just feels sloppy and may be insecure in some way. Is there a better way to do this in Bash?

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  • When is lazy evaluation not useful?

    - by Cherian
    Delay execution is almost always a boon. But then there are cases when it’s a problem and you resort to “fetch” (in Nhibernate) to eager fetch it. Do you know practical situations when lazy evaluation can bite you back…?

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  • Project Performance Evaluation and Finding Weak Areas

    - by pramodc84
    I'm working in J2EE web project, which has lots of Java, SQL scripts, JS, AJAX stuff. Its been 5 years for project still running fine. I have assigned with work of performance evaluation on the project as there might be some memory usage issues, DB fetching logic delays and other similar weak performance areas. From where should I begin? Any best practices to make project better?

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  • Where are the clever uses of strict evaluation?

    - by devonrt
    It seems like there are plenty of examples of clever things being done in a lazily-evaluated language that can't be done in an environment with strict evaluation. For example infinite lists in Haskell or replacing every element in a tree with the tree's minimum value in one pass. Are there any examples of clever things being done in a strictly-evaluated language that can't easily be done in a lazily-evaluated language?

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  • MSSQL 2005: Update rows in a specified order (like ORDER BY)?

    - by JMTyler
    I want to update rows of a table in a specific order, like one would expect if including an ORDER BY clause, but MS SQL does not support the ORDER BY clause in UPDATE queries. I have checked out this question which supplied a nice solution, but my query is a bit more complicated than the one specified there. UPDATE TableA AS Parent SET Parent.ColA = Parent.ColA + (SELECT TOP 1 Child.ColA FROM TableA AS Child WHERE Child.ParentColB = Parent.ColB ORDER BY Child.Priority) ORDER BY Parent.Depth DESC; So, what I'm hoping that you'll notice is that a single table (TableA) contains a hierarchy of rows, wherein one row can be the parent or child of any other row. The rows need to be updated in order from the deepest child up to the root parent. This is because TableA.ColA must contain an up-to-date concatenation of its own current value with the values of its children (I realize this query only concats with one child, but that is for the sake of simplicity - the purpose of the example in this question does not necessitate any more verbosity), therefore the query must update from the bottom up. The solution suggested in the question I noted above is as follows: UPDATE messages SET status=10 WHERE ID in (SELECT TOP (10) Id FROM Table WHERE status=0 ORDER BY priority DESC ); The reason that I don't think I can use this solution is because I am referencing column values from the parent table inside my subquery (see WHERE Child.ParentColB = Parent.ColB), and I don't think two sibling subqueries would have access to each others' data. So far I have only determined one way to merge that suggested solution with my current problem, and I don't think it works. UPDATE TableA AS Parent SET Parent.ColA = Parent.ColA + (SELECT TOP 1 Child.ColA FROM TableA AS Child WHERE Child.ParentColB = Parent.ColB ORDER BY Child.Priority) WHERE Parent.Id IN (SELECT Id FROM TableA ORDER BY Parent.Depth DESC); The WHERE..IN subquery will not actually return a subset of the rows, it will just return the full list of IDs in the order that I want. However (I don't know for sure - please tell me if I'm wrong) I think that the WHERE..IN clause will not care about the order of IDs within the parentheses - it will just check the ID of the row it currently wants to update to see if it's in that list (which, they all are) in whatever order it is already trying to update... Which would just be a total waste of cycles, because it wouldn't change anything. So, in conclusion, I have looked around and can't seem to figure out a way to update in a specified order (and included the reason I need to update in that order, because I am sure I would otherwise get the ever-so-useful "why?" answers) and I am now hitting up Stack Overflow to see if any of you gurus out there who know more about SQL than I do (which isn't saying much) know of an efficient way to do this. It's particularly important that I only use a single query to complete this action. A long question, but I wanted to cover my bases and give you guys as much info to feed off of as possible. :) Any thoughts?

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  • SQL Server 2005: Update rows in a specified order (like ORDER BY)?

    - by JMTyler
    I want to update rows of a table in a specific order, like one would expect if including an ORDER BY clause, but SQL Server does not support the ORDER BY clause in UPDATE queries. I have checked out this question which supplied a nice solution, but my query is a bit more complicated than the one specified there. UPDATE TableA AS Parent SET Parent.ColA = Parent.ColA + (SELECT TOP 1 Child.ColA FROM TableA AS Child WHERE Child.ParentColB = Parent.ColB ORDER BY Child.Priority) ORDER BY Parent.Depth DESC; So, what I'm hoping that you'll notice is that a single table (TableA) contains a hierarchy of rows, wherein one row can be the parent or child of any other row. The rows need to be updated in order from the deepest child up to the root parent. This is because TableA.ColA must contain an up-to-date concatenation of its own current value with the values of its children (I realize this query only concats with one child, but that is for the sake of simplicity - the purpose of the example in this question does not necessitate any more verbosity), therefore the query must update from the bottom up. The solution suggested in the question I noted above is as follows: UPDATE messages SET status=10 WHERE ID in (SELECT TOP (10) Id FROM Table WHERE status=0 ORDER BY priority DESC ); The reason that I don't think I can use this solution is because I am referencing column values from the parent table inside my subquery (see WHERE Child.ParentColB = Parent.ColB), and I don't think two sibling subqueries would have access to each others' data. So far I have only determined one way to merge that suggested solution with my current problem, and I don't think it works. UPDATE TableA AS Parent SET Parent.ColA = Parent.ColA + (SELECT TOP 1 Child.ColA FROM TableA AS Child WHERE Child.ParentColB = Parent.ColB ORDER BY Child.Priority) WHERE Parent.Id IN (SELECT Id FROM TableA ORDER BY Parent.Depth DESC); The WHERE..IN subquery will not actually return a subset of the rows, it will just return the full list of IDs in the order that I want. However (I don't know for sure - please tell me if I'm wrong) I think that the WHERE..IN clause will not care about the order of IDs within the parentheses - it will just check the ID of the row it currently wants to update to see if it's in that list (which, they all are) in whatever order it is already trying to update... Which would just be a total waste of cycles, because it wouldn't change anything. So, in conclusion, I have looked around and can't seem to figure out a way to update in a specified order (and included the reason I need to update in that order, because I am sure I would otherwise get the ever-so-useful "why?" answers) and I am now hitting up Stack Overflow to see if any of you gurus out there who know more about SQL than I do (which isn't saying much) know of an efficient way to do this. It's particularly important that I only use a single query to complete this action. A long question, but I wanted to cover my bases and give you guys as much info to feed off of as possible. :) Any thoughts?

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  • Minimax algorithm: Cost/evaluation function?

    - by Dave
    Hi guys, A school project has me writing a Date game in C++ (example at http://www.cut-the-knot.org/Curriculum/Games/Date.shtml) where the computer player must implement a Minimax algorithm with alpha-beta pruning. Thus far, I understand what the goal is behind the algorithm in terms of maximizing potential gains while assuming the opponent will minify them. However, none of the resources I read helped me understand how to design the evaluation function the minimax bases all it's decisions on. All the examples have had arbitrary numbers assigned to the leaf nodes, however, I need to actually assign meaningful values to those nodes. Intuition tells me it'd be something like +1 for a win leaf node, and -1 for a loss, but how do intermediate nodes evaluate? Any help would be most appreciated.

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  • Sudoku solver evaluation function

    - by Rich
    Hi, So I'm trying to write a simple genetic algorithm for solving a sudoku (not the most efficient way, I know, but it's just to practice evolutionary algorithms). I'm having some problems coming up with an efficient evaluation function to test if the puzzle is solved or not and how many errors there are. My first instinct would be to check if each row and column of the matrix (doing it in octave, which is similar to matlab) have unique elements by ordering them, checking for duplicates and then putting them back the way they were, which seems long winded. Any thoughts? Sorry if this has been asked before...

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  • Oracle SQL clause evaluation order

    - by jon.johnson
    In Oracle, which clause types get evaluated first? If I had the following ( pretend .... represent valid expressions and relation names ), what would the order of evaluation be? SELECT ... FROM ..... WHERE ........ GROUP BY ........... HAVING ............. ORDER BY ................ I am under the impression that the SELECT clause is evaluated last, but other than that I'm clueless.

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  • Lazy evaluation with ostream C++ operators

    - by SavinG
    I am looking for a portable way to implement lazy evaluation in C++ for logging class. Let's say that I have a simple logging function like void syslog(int priority, const char *format, ...); then in syslog() function we can do: if (priority < current_priority) return; so we never actually call the formatting function (sprintf). On the other hand, if we use logging stream like log << LOG_NOTICE << "test " << 123; all the formating is always executed, which may take a lot of time. Is there any possibility to actually use all the goodies of ostream (like custom << operator for classes, type safety, elegant syntax...) in a way that the formating is executed AFTER the logging level is checked ?

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  • Oracle Sun Solaris 11.1 Completes EAL4+ Common Criteria Evaluation

    - by Joshua Brickman-Oracle
    Oracle is pleased to announce that the Oracle Solaris 11.1 operating system has achieved a Common Criteria certification at Evaluation Assurance Level (EAL) 4 augmented by Flaw Remediation under the Canadian Communications Security Establishment’s (CSEC) Canadian Common Criteria  Scheme (CCCS).  EAL4 is the highest level achievable for commercial software, and is the highest level mutually recognized by 26 countries under the current Common Criteria Recognition Arrangement (CCRA).  Oracle Solaris 11.1 is conformant to the BSI Operating System Protection Profile v2.0 with the following four extended packages. (1) Advanced Management, (2) Extended Identification and Authentication, (3) Labeled Security, and (4) Virtualization. Common Criteria is an international framework (ISO/IEC 15408) which defines a common approach for evaluating security features and capabilities of Information Technology security products. A certified product is one that a recognized Certification Body asserts as having been evaluated by a qualified, accredited, and independent evaluation laboratory competent in the field of IT security evaluation to the requirements of the Common Criteria and Common Methodology for Information Technology Security Evaluation. Oracle Solaris is the industry’s most widely deployed UNIXtm operating system, delivers mission critical cloud infrastructure with built-in virtualization, simplified software lifecycle management, cloud scale data management, and advanced protection for public, private, and hybrid cloud environments. It provides a suite of technologies and applications that create an operating system with optimal performance. Oracle Solaris 11.1 includes key technologies such as Trusted Extensions, the Oracle Solaris Cryptographic Framework, Zones, the ZFS File System, Image Packaging System (IPS), and multiple boot environments. The Oracle Solaris 11.1 Certification Report and Security Target can be viewed on the Communications Security Establishment Canada (CSEC) site and on the Common Criteria Portal. For more information on Oracle’s participation in the Common Criteria program, please visit the main Common Criteria information page here: (http://www.oracle.com/technetwork/topics/security/oracle-common-criteria-095703.html) For a complete list of Oracle products with Common Criteria certifications and FIPS 140-2 validations, please see the Security Evaluations website here: (http://www.oracle.com/technetwork/topics/security/security-evaluations-099357.html).

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  • Reversi/Othello early-game evaluation function

    - by Vladislav Il'ushin
    I've written my own Reversi player, based on the MiniMax algorithm, with Alpha-Beta pruning, but in the first 10 moves my evaluation function is too slow. I need a good early-game evaluation function. I'm trying to do it with this matrix (corresponding to the board) which determines how favourable that square is to have: { 30, -25, 10, 5, 5, 10, -25, 30,}, {-25, -25, 1, 1, 1, 1, -25, -25,}, { 10, 1, 5, 2, 2, 5, 1, 10,}, { 5, 1, 2, 1, 1, 2, 1, 5,}, { 5, 1, 2, 1, 1, 2, 1, 5,}, { 10, 1, 5, 2, 2, 5, 1, 10,}, {-25, -25, 1, 1, 1, 1, -25, -25,}, { 30, -25, 10, 5, 5, 10, -25, 30,},}; But it doesn't work well. Have you even written an early-game evaluation function for Reversi?

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  • Is it possible to upgrade using the Windows Server 2012 evaluation?

    - by Cerebrate
    I've got a Windows Server 2008 Standard installation here that I'm trying to upgrade to Windows Server 2012 Server, using the evaluation version. (The scenario is essentially that I need to test the upgrade, and specifically the upgrade process, before we spend the money on going ahead with the actual upgrade.) When I try to upgrade, it fails with the message: "Windows Server 2008 Standard cannot be upgraded to Windows Server 2012 Standard Evaluation (Server with a GUI). You can choose to install a new... (etc., etc.)" Is this (non-upgradability) a known limitation of the evaluation version? (Unfortunately, I haven't found a clear answer on this point.) And if not, any thoughts on where else I might look for the problem and solutions to it?

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  • Working out global tab order algorithmically?

    - by Mrgreen
    We have a proprietry system where we can configure fields on indiviual forms. However these fields have a global tab order (we cannot specify for a specific form). We have a bunch of forms (35 in total) which share a lot of different fields. Each form has a specific tab/edit order that needs to be configured. Example: Form 1 has fields A,B,C,D in that order. Form 2 has fields E,F,G,A in that order. Form 3 has fields E,B,H,I in that order. The global tab orders would be E,F,G,A,B,C,D,H,I Notice how A needs to come before B yet after G. Is there any easy way to work this out using the tab order lists for each form? I need to merge this tab order information into a single global tab order list. I have over 200 fields in total and it is near impossible to do by hand.

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  • Search results in wordpress, order by custom category order and time DESC

    - by Adiasz
    Hello I want to change default post search order to order: sample cat 1 sample post from cat 1 sample post from cat 1 sample cat 2 sample post from cat 2 sample post from cat 3 sample cat 3 etc.. So... I want to define category order and in search results will be sorted for this order and in category order will be date DESC. Only posts (no categories) will be visible. Anybody have any idea?

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  • Evaluation of Haskell Statements/Expressions using GHC API

    - by Cetin Sert
    For a tool I'm writing ( http://hackage.haskell.org/package/explore ) I need a way to read haskell function definitions at run-time, apply them to values from my tool and retrieve the results of their application. Can anyone give me a very basic example using GHC (6.10.4 or 6.12.1) API? example function definition to be read from a file at run-time: f x = 10**(((4/1102)*x)-1) expected program output --mapM_ print $ map f [428, 410, 389] 3.577165388142748 3.077536885227335 2.5821307011665815

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  • Can someone please explain this lazy evaluation code?

    - by Tejs
    So, this question was just asked on SO: http://stackoverflow.com/questions/2740001/how-to-handle-an-infinite-ienumerable My sample code: public static void Main(string[] args) { foreach (var item in Numbers().Take(10)) Console.WriteLine(item); Console.ReadKey(); } public static IEnumerable<int> Numbers() { int x = 0; while (true) yield return x++; } Can someone please explain why this is lazy evaluated? I've looked up this code in Reflector, and I'm more confused than when I began. Reflector outputs: public static IEnumerable<int> Numbers() { return new <Numbers>d__0(-2); } For the numbers method, and looks to have generated a new type for that expression: [DebuggerHidden] public <Numbers>d__0(int <>1__state) { this.<>1__state = <>1__state; this.<>l__initialThreadId = Thread.CurrentThread.ManagedThreadId; } This makes no sense to me. I would have assumed it was an infinite loop until I put that code together and executed it myself.

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  • Haskell Lazy Evaluation and Reuse

    - by Jonathan Sternberg
    I know that if I were to compute a list of squares in Haskell, I could do this: squares = [ x ** 2 | x <- [1 ..] ] Then when I call squares like this: print $ take 4 squares And it would print out [1.0, 4.0, 9.0, 16.0]. This gets evaluated as [ 1 ** 2, 2 ** 2, 3 ** 2, 4 ** 2 ]. Now since Haskell is functional and the result would be the same each time, if I were to call squares again somewhere else, would it re-evaluate the answers it's already computed? If I were to re-use squares after I had already called the previous line, would it re-calculate the first 4 values? print $ take 5 squares Would it evaluate [1.0, 4.0, 9.0, 16.0, 5 ** 2]?

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  • Understanding evaluation of expressions containing '++' and '->' operators in C.

    - by Leif Ericson
    Consider this example: struct { int num; } s, *ps; s.num = 0; ps = &s; ++ps->num; printf("%d", s.num); /* Prints 1 */ It prints 1. So I understand that it is because according to operators precedence, -> is higher than ++, so the value ps->num (which is 0) is firstly fetched and then the ++ operator operates on it, so it increments it to 1. struct { int num; } s, *ps; s.num = 0; ps = &s; ps++->num; printf("%d", s.num); /* Prints 0 */ In this example I get 0 and I don't understand why; the explanation of the first example should be the same for this example. But it seems that this expression is evaluated as follows: At first, the operator ++ operates, and it operates on ps, so it increments it to the next struct. Only then -> operates and it does nothing because it just fetches the num field of the next struct and does nothing with it. But it contradicts the precedence of operators, which says that -> have higher precedence than ++. Can someone explain this behavior? Edit: After reading two answers which refer to a C++ precedence tables which indicate that a prefix ++/-- operators have lower precedence than ->, I did some googling and came up with this link that states that this rule applies also to C itself. It fits exactly and fully explains this behavior, but I must add that the table in this link contradicts a table in my own copy of K&R ANSI C. So if you have suggestions as to which source is correct I would like to know. Thanks.

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  • Unsure of how to get the right evaluation order

    - by Matt Fenwick
    I'm not sure what the difference between these two pieces of code is (with respect to x), but the first one completes: $ foldr (\x y -> if x == 4 then x else x + y) 0 [1,2 .. ] 10 and the second one doesn't (at least in GHCi): $ foldr (\x (y, n) -> if x == 4 then (x, n) else (x + y, n + 1)) (0, 0) [1,2 .. ] ....... What am I doing wrong that prevents the second example from completing when it hits x == 4, as in the first one? I've tried adding bang-patterns to both the x and to the x == 4 (inside a let) but neither seems to make a difference.

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  • JavaScript: How to reverse order=[] arrays from last to first?

    - by Binyamin
    My js code does POST order.php?order[]=1&order[]=2&order[]=3&order[]=4&order[]=5&&action=update How to reverse it to order.php?order[]=5&order[]=4&order[]=3&order[]=2&order[]=1&&action=update ? JavaScript: order=[]; //var reversed = $(this).sortable("serialize").split("&").reverse().join("&"); //var order = reversed + '&action=update'; //unfortunately it does not work so $('#list ul').children('li').each(function(idx, elm) { order.push(elm.id.split('-')[1]) }); $.post('order.php', {'order[]': order, action: 'update'}); HTML: <ul> <li id="oreder-5">5</li> <li id="oreder-4">4</li> <li id="oreder-3">3</li> <li id="oreder-2">2</li> <li id="oreder-1">1</li> <ul>

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