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• Can LINQ expression classes implement the observer pattern instead of deferred execution?

  - by Tormod

  Hi. We have issues within an application using a state machine. The application is implemented as a windows service and is iteration based (it "foreaches" itself through everything) and there are myriads of instances being processed by the state machine. As I'm reading the MEAP version of Jon Skeets book "C# in Depth, 2nd ed", I'm wondering if I can change the whole thing to use linq expression instances so that guards and conditions are represented using expression trees. We are building many applications on this state machine engine and would probably greatly benefit from the new Expression tree visualizer in VS 2010 Now, simple example. If I have an expression tree where there is an OR Expression condition with two sub nodes, is there any way that these can implement the observer pattern so that the expression tree becomes event driven? If a condition change, it should notify its parent node (the OR node). Since the OR node then changes from "false" to "true", then it should notify ITS parent and so on. I love the declarative model of expression trees, but the deferred execution model works in opposite direction of the control flow if you want event based "live" conditions. Am I off on a wild goose chase here? Or is there some concept in the BCL that may help me achieve this?

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• bind event handler on keydown listen function JavaScript jQuery

  - by user1644123

  I am trying to bind a handler to an event. The event is a keydown function. The handler will listen for hit variables to produce one of two conditions. The 1st condition (odd number of hits) will perform 1 function, the 2nd (even number of hits) will perform another function. To elaborate, the 1st function will scroll to one element, the 2nd will scroll to another element. My syntax may be the wrong approach, but it works for the 1st condition, but not the 2nd. I think I have the conditional statement in the wrong place. How can I rewrite this to work as intended? Thank you kindly, in advance! $(document).keydown(function(e) { switch (e.which) { case 37: break; case 38: break; case 39: break; case 40: //bottom arrow key var hits = 0; if (hits % 2 !== 0) { $('#wrap').animate({ scrollTop: $("#scrollToHere").offset().top }, 2800); } else { $('#wrap').animate({ scrollTop: $("#scroll2ToHere").offset().top }, 2800); } hits++; return false; break; } })? *I moved "var hits = 0;" to the top, but it only works! But is there a way I can reset the whole thing after every two hits? I want to reset because when there is a bug and if I press a 3rd time it scrolls to the very top of the page, where there is no element to make it scroll to the top. Why would it scroll to the top of the page if I never scripted it to do so?? *

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• ControlCollection extension method optimazation

  - by Johan Leino

  Hi, got question regarding an extension method that I have written that looks like this: public static IEnumerable<T> FindControlsOfType<T>(this ControlCollection instance) where T : class { T control; foreach (Control ctrl in instance) { if ((control = ctrl as T) != null) { yield return control; } foreach (T child in FindControlsOfType<T>(ctrl.Controls)) { yield return child; } } } public static IEnumerable<T> FindControlsOfType<T>(this ControlCollection instance, Func<T, bool> match) where T : class { return FindControlsOfType<T>(instance).Where(match); } The idea here is to find all controls that match a specifc criteria (hence the Func<..) in the controls collection. My question is: Does the second method (that has the Func) first call the first method to find all the controls of type T and then performs the where condition or does the "runtime" optimize the call to perform the where condition on the "whole" enumeration (if you get what I mean). secondly, are there any other optimizations that I can do to the code to perform better. An example can look like this: var checkbox = this.Controls.FindControlsOfType<MyCustomCheckBox>( ctrl => ctrl.CustomProperty == "Test" ) .FirstOrDefault();

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• Odd 'UNION' behavior in an Oracle SQL query

  - by RenderIn

  Here's my query: SELECT my_view.* FROM my_view WHERE my_view.trial in (select 2 as trial_id from dual union select 3 from dual union select 4 from dual) and my_view.location like ('123-%') When I execute this query it returns results which do not conform to the my_view.location like ('123-%') condition. It's as if that condition is being ignored completely. I can even change it to my_view.location IS NULL and it returns the same results, despite that field being not-nullable. I know this query seems ridiculous with the selects from dual, but I've structured it this way to replicate a problem I have when I use a 'WITH' clause (the results of that query are where the selects from dual inline view are). I can modify the query like so and it returns the expected results: SELECT my_view.* FROM my_view WHERE my_view.trial in (2, 3, 4) and my_view.location like ('123-%') Unfortunately I do not know the trial values up front (they are queried for in a 'WITH' clause) so I cannot structure my query this way. What am I doing wrong? I will say that the my_view view is composed of 3 other views whose results are UNION ALL and each of which retrieve some data over a DB Link. Not that I believe that should matter, but in case it does.

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• R - removing rows and replacing values using conditions from multiple columns

  - by lecodesportif

  I want to filter out all values of var3 < 5 while keeping at least one occurrence of each value of var1. > foo <- data.frame(var1= c(1, 1, 2, 3, 3, 4, 4, 5), var2=c(9, 5, 13, 9, 12, 11, 13, 9), var3=c(6, 8, 3, 6, 4, 7, 2, 9)) > foo var1 var2 var3 1 1 9 6 2 1 5 8 3 2 13 3 4 3 9 6 5 3 12 4 6 4 11 7 7 4 13 2 8 5 9 9 subset(foo, (foo$var3>=5)) would remove row 3, 5 and 7 and I would have lost var1==2. I want to remove the row if there is another value of var1 that fulfills the condition foo$var3 = 5. See row 5. I want to keep the row, assiging NA to var2 and var3 if all occurrences of a value var1 do not fulfill the condition foo$var3 = 5. This is the result I expect: var1 var2 var3 1 1 9 6 2 1 5 8 3 2 NA NA 4 3 9 6 6 4 11 7 8 5 9 9 This is the closest I got: > foo$var3[ foo$var3 < 5 ] = NA > foo$var2[ is.na(foo$var3) ] = NA > foo var1 var2 var3 1 1 9 6 2 1 5 8 3 2 NA NA 4 3 9 6 5 3 NA NA 6 4 11 7 7 4 NA NA 8 5 9 9 So I guess I just need to know how to conditionally remove the row.

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• select query from mysql_num_rows

  - by Andi Nugroho

  i want create multiple search where statement $where_search is a multiple condition from post form. but stil error when iam using this code ".where_search." in where condition with mysql_num_rows for paging $tampil2 = mysql_query("SELECT * FROM bb where ".$where_search." and kd_kelompok='2' and kd_komoditi='11' and nm_sebutan IS NOT NULL " ); this is the complete code. $where_search = "kd_pok='2' and kd_komoditi='11' "; if (isset($_POST['lakpus'])) { if (empty($_POST['lakpus'])) { } else { if (empty($where_search)) { $where_search .= "lakpus = '$lakpus' "; } else { $where_search .= "AND lakpus = '$lakpus' "; } } } if (isset($_POST['kd_por'])) { $kd_por = $_POST['kd_por'] ; if (empty($_POST['kd_por'])) { } else { if (empty($where_search)) { $where_search .= "kd_por = '$kd_por' "; } else { $where_search .= "AND tab1.kd_por = '$kd_por' "; } } } $max=15; $tampil2 = mysql_query("SELECT * FROM bb where ".$where_search." and kd_kelompok='2' and kd_komoditi='11' and nm_sebutan IS NOT NULL " ); $jml = mysql_num_rows($tampil2); $jmlhal = ceil($jml/$max);

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• Storing array as value in associative array

  - by Jagannath

  i have a problem where I need to have an array as value in associative array. Go through the code below. Here I am trying to loop the files in a directory and it is more likely that more than 1 file can have the same ctrno. So, I would like to see what are all the files having the same ctrno. The code below gives error at "$ctrno_hash[$ctrno] = @arr;" in the else condition. The same case would be for if condition as well. Am I following the right approach or could it be done diffently? sub loop_through_files { $file = "@_"; open(INPFILE, "$file") or die $!; #print "$file:$ctrno\n"; while (<INPFILE>) { $line .= $_; } if ($line =~ /$ctrno/ ) { print "found\n"; if ( exists $ctrno_hash[$ctrno]) { local @arr = $ctrno_hash[$ctrno]; push (@arr, $file); $ctrno_hash[$ctrno] = @arr; } else { local @arr; push(@arr, $file); $ctrno_hash[$ctrno] = @arr; } } }

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• Could DataGridView be this dumb? or its me?lol

  - by Selase

  Am trying to bind data to a dropdown list on pageload based on a condition. Code explains further below. public partial class AddExhibit : System.Web.UI.Page { string adminID, caseIDRetrieved; DataSet caseDataSet = new DataSet(); SqlDataAdapter caseSqlDataAdapter = new SqlDataAdapter(); string strConn = WebConfigurationManager.ConnectionStrings["CMSSQL3ConnectionString1"].ConnectionString; protected void Page_Load(object sender, EventArgs e) { adminID = Request.QueryString["adminID"]; caseIDRetrieved = Request.QueryString["caseID"]; if (caseIDRetrieved != null) { CaseIDDropDownList.Text = caseIDRetrieved; //CaseIDDropDownList.Enabled = false; } else { try { CreateDataSet(); DataView caseDataView = new DataView(caseDataSet.Tables[0]); CaseIDDropDownList.DataSource = caseDataView; CaseIDDropDownList.DataBind(); } catch (Exception ex) { string script = "<script>alert('" + ex.Message + "');</script>"; } } } The CreateDataset method that is called in the if..else statement is contains the following code. private void CreateDataSet() { SqlConnection caseConnection = new SqlConnection(strConn); caseSqlDataAdapter.SelectCommand = new SqlCommand("Select CaseID FROM Cases", caseConnection); caseSqlDataAdapter.Fill(caseDataSet); } However when i load the page and as usual the condition that is supposed to bid the data is met, the gridview decides to displays as follows... IS IT ME OR ITS THE DATAGRID?...??

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• Does "epsilon" really guarantees anything in floating-point computations?!

  - by Michal Czardybon

  To make the problem short let's say I want to compute expression: a / (b - c) on float's. To make sure the result is meaningful, I can check if 'b' and 'c' are inequal: float eps = std::numeric_limits<float>::epsilon(); if ((b - c) > EPS || (c - b) > EPS) { return a / (b - c); } but my tests show it is not enough to guarantee either meaningful results nor not failing to provide a result if it is possible. Case 1: a = 1.0f; b = 0.00000003f; c = 0.00000002f; Result: The if condition is NOT met, but the expression would produce a correct result 100000008 (as for the floats' precision). Case 2: a = 1e33f; b = 0.000003; c = 0.000002; Result: The if condition is met, but the expression produces not a meaningful result +1.#INF00. I found it much more reliable to check the result, not the arguments: const float INF = numeric_limits<float>::infinity(); float x = a / (b - c); if (-INF < x && x < INF) { return x; } But what for is the epsilon then and why is everyone saying epsilon is good to use?

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• How might I wrap the FindXFile-style APIs to the STL-style Iterator Pattern in C++?

  - by BillyONeal

  Hello everyone :) I'm working on wrapping up the ugly innards of the FindFirstFile/FindNextFile loop (though my question applies to other similar APIs, such as RegEnumKeyEx or RegEnumValue, etc.) inside iterators that work in a manner similar to the Standard Template Library's istream_iterators. I have two problems here. The first is with the termination condition of most "foreach" style loops. STL style iterators typically use operator!= inside the exit condition of the for, i.e. std::vector<int> test; for(std::vector<int>::iterator it = test.begin(); it != test.end(); it++) { //Do stuff } My problem is I'm unsure how to implement operator!= with such a directory enumeration, because I do not know when the enumeration is complete until I've actually finished with it. I have sort of a hack together solution in place now that enumerates the entire directory at once, where each iterator simply tracks a reference counted vector, but this seems like a kludge which can be done a better way. The second problem I have is that there are multiple pieces of data returned by the FindXFile APIs. For that reason, there's no obvious way to overload operator* as required for iterator semantics. When I overload that item, do I return the file name? The size? The modified date? How might I convey the multiple pieces of data to which such an iterator must refer to later in an ideomatic way? I've tried ripping off the C# style MoveNext design but I'm concerned about not following the standard idioms here. class SomeIterator { public: bool next(); //Advances the iterator and returns true if successful, false if the iterator is at the end. std::wstring fileName() const; //other kinds of data.... }; EDIT: And the caller would look like: SomeIterator x = ??; //Construct somehow while(x.next()) { //Do stuff } Thanks! Billy3

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• Type result with Ternary operator in C#

  - by Vaccano

  I am trying to use the ternary operator, but I am getting hung up on the type it thinks the result should be. Below is an example that I have contrived to show the issue I am having: class Program { public static void OutputDateTime(DateTime? datetime) { Console.WriteLine(datetime); } public static bool IsDateTimeHappy(DateTime datetime) { if (DateTime.Compare(datetime, DateTime.Parse("1/1")) == 0) return true; return false; } static void Main(string[] args) { DateTime myDateTime = DateTime.Now; OutputDateTime(IsDateTimeHappy(myDateTime) ? null : myDateTime); Console.ReadLine(); ^ } | } | // This line has the compile issue ---------------+ On the line indicated above, I get the following compile error: Type of conditional expression cannot be determined because there is no implicit conversion between '< null ' and 'System.DateTime' I am confused because the parameter is a nullable type (DateTime?). Why does it need to convert at all? If it is null then use that, if it is a date time then use that. I was under the impression that: condition ? first_expression : second_expression; was the same as: if (condition) first_expression; else second_expression; Clearly this is not the case. What is the reasoning behind this? (NOTE: I know that if I make "myDateTime" a nullable DateTime then it will work. But why does it need it? As I stated earlier this is a contrived example. In my real example "myDateTime" is a data mapped value that cannot be made nullable.)

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• ControlCollection extension method optimization

  - by Johan Leino

  Hi, got question regarding an extension method that I have written that looks like this: public static IEnumerable<T> FindControlsOfType<T>(this ControlCollection instance) where T : class { T control; foreach (Control ctrl in instance) { if ((control = ctrl as T) != null) { yield return control; } foreach (T child in FindControlsOfType<T>(ctrl.Controls)) { yield return child; } } } public static IEnumerable<T> FindControlsOfType<T>(this ControlCollection instance, Func<T, bool> match) where T : class { return FindControlsOfType<T>(instance).Where(match); } The idea here is to find all controls that match a specifc criteria (hence the Func<..) in the controls collection. My question is: Does the second method (that has the Func) first call the first method to find all the controls of type T and then performs the where condition or does the "runtime" optimize the call to perform the where condition on the "whole" enumeration (if you get what I mean). secondly, are there any other optimizations that I can do to the code to perform better. An example can look like this: var checkbox = this.Controls.FindControlsOfType<MyCustomCheckBox>( ctrl => ctrl.CustomProperty == "Test" ) .FirstOrDefault();

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• C++: static assert for const variables?

  - by shoosh

  Static asserts are very convenient for checking things in compile time. A simple static assert idiom looks like this: template<bool> struct StaticAssert; template<> struct StaticAssert<true> {}; #define STATIC_ASSERT(condition) do { StaticAssert<condition>(); } while(0) This is good for stuff like STATIC_ASSERT(sizeof(float) == 4) and: #define THIS_LIMIT (1000) ... STATIC_ASSERT(THIS_LIMIT > OTHER_LIMIT); But using #define is not the "C++" way of defining constants. C++ would have you use an anonymous namespace: namespace { const int THIS_LIMIT = 1000; } or even: static const int THIS_LIMIT = 1000; The trouble with this is that with a const int you can't use STATIC_ASSERT() and you must resort to a run-time check which is silly. Is there a way to properly solve this in current C++? I think I've read C++0x has some facility to do this...

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• how to assign the html value to the php variable without post or get method

  - by Meena

  hi , in my program i had a php value $test = 2 using this value i done some operation for example: in my page i had a 2 block A and B and one select box. If the test value is A it enable the div A, if the value is B it hide div A and also i am able to show and hide the div using the select box onchange event. please check my sample code given below $test = $_GET["id"]; <select name="hideme" id="hideme" onchange="enableme();"> <option value="A">Show</option> <option value="B">Hide</option> </select> if($test == 'A') { <div id="div1" name="div1"> xxxxxxxxxxxxx </div> } Js Function : function enableme() { if(document.getElementByID('hideme').value == "A") { document.getElementById.style.display ="block"; } else { document.getElementById.style.display ="none"; } } my issue is at fist time using the $test($_get) value it show the correct div but the on change event is not working because of , if condition. If i remove the if condition then it show div A even if the value of the $test is B. how could i handle both. Please Help me

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• problem in handling menu - submenu based on spring security

  - by Nirmal

  Hi All... I have configured spring security core plugin using requestmap table inside the database.. Now inside requestmap table I have all the possible urls and it's equivalent roles who can access that url... Now I want to generate menus and submenus based on the urls stored in requestmap table... So my requirement is to check the urls of menu & submenus against the logged in users privileges... And if logged in user has any one privilege then I need to display that main menu and the available submenus.... For e.g. I have a menu in my project called user which has a following submenus : **Users (main menu)** Manage Users (sub menu) Import Users (sub menu) Now inside my header.gsp I have successfully achieved the above requirement using if else condition, like : if ( privs.contains("/users/manageUsers") || privs.contains("/users/importUsers")) here privs are the list of urls from requestmap table for logged in user. But I want to achieve these using spring security tag lib, so for comparing urls I have find following tag from spring security core documentation : <sec:access url="/users/manageUsers"> But i am bit confuse that how I can replace or condition using tag library.. Is there any tag available which checks from multiple urls and evaluate it to true or false ? Of course I can do using sec:access tag with some flag logic, but is there any tags available which can fulfill my requirement directly ? Thanks in advance...

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• Can we run two simultaneous non-nested loops in Perl?

  - by Mike

  Part of my code goes like this: while(1){ my $winmm = new Win32::MediaPlayer; $winmm->load('1.mp3'); $winmm->play; $winmm->volume(100); Do Some Stuff; last if some condition is met; } Problem is: I want the music to be always on when I'm in the Do Some Stuff stage in the while loop. But the length of the music is so short that it will come to a full stop before I go to the next stage, so I want the music to repeat itself, but the Win32::Mediaplayer module does not seem to have a repeat mode, so I'm thinking of doing an infinite loop for the music playing part. Like this: while(1){ my $winmm = new Win32::MediaPlayer; $winmm->load('1.mp3'); $winmm->play; $winmm->volume(100); } while(2){ Do some stuff; last if some condition is met } But based on my current Perl knowledge if I'm in the while(1) part, I can never go to the while(2) part. Even if it comes to a nested loop, I have to do something to break out of the inside loop before going to the other part of the outside loop. The answer to my question "Can we run two simultaneous non-nested loops in Perl?" may be a NO, but I assume there is some way of handling such situation. Correct me if I'm wrong. Thanks as always for any comments/suggestions :) UPDATE I really appreciate the help from everyone. Thanks :) So the answer to my question is a YES, not a NO. I'm happy that I've learned how to use fork() and threads to solve a real problem :)

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• Pushing a vector into an vector

  - by Sunil

  I have a 2d vector typedef vector <double> record_t; typedef vector <record_t> data_t; data_t data; So my 2d vector is data here. It has elements like say, 1 1 1 1 1 2 2 2 2 2 3 3 3 3 3 4 4 4 4 4 5 5 5 5 5 Now I want to insert these elements into another 2d vector std::vector< vector<double> > window; So what I did was to create an iterator for traversing through the rows of data and pushing it into window like std::vector< std::vector<double> >::iterator data_it; for (data_it = data.begin() ; data_it != data.end() ; ++data_it){ window.push_back ( *data_it ); // Do something else } Can anybody tell me where I'm wrong or suggest a way to do this ? BTW I want to push it just element by element because I want to be able to do something else inside the loop too. i.e. I want to check for a condition and increment the value of the iterator inside. for example, if a condition satisfies then I'll do data_it+=3 or something like that inside the loop. Thanks P.S. I asked this question last night and didn't get any response and that's why I'm posting it again.

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• Ant path/pathelement not expanding properties correctly

  - by Jonas Byström

  My property gwt.sdk expands just fine everywhere else, but not inside a path/pathelement: <target name="setup.gwtenv"> <property environment="env"/> <condition property="gwt.sdk" value="${env.GWT_SDK}"> <isset property="env.GWT_SDK" /> </condition> <property name="gwt.sdk" value="/usr/local/gwt" /> <!-- Default value. --> </target> <path id="project.class.path"> <pathelement location="${gwt.sdk}/gwt-user.jar"/> </path> <target name="libs" depends="setup.gwtenv" description="Copy libs to WEB-INF/lib"> </target> <target name="javac" depends="libs" description="Compile java source"> <javac srcdir="src" includes="**" encoding="utf-8" destdir="war/WEB-INF/classes" source="1.5" target="1.5" nowarn="true" debug="true" debuglevel="lines,vars,source"> <classpath refid="project.class.path"/> </javac> </target> For instance, placing an echo of ${gwt.sdk} just above works, but not inside "project.class.path". Is it a bug, or do I have to do something that I'm not? Edit: I tried moving the property out from target setup.gwtenv into "global space", that helped circumvent the problem.

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• Why do I get null objects in a many-to-many bag?

  - by Jim Geurts

  I have a bag defined for a many-to-many list: <class name="Author" table="Authors"> <id name="Id" column="AuthorId"> <generator class="identity" /> </id> <property name="Name" /> <bag name="Books" table="Author_Book_Map" where="IsDeleted=0" fetch="join"> <key column="AuthorId" /> <many-to-many class="Book" column="BookId" where="IsDeleted=0" /> </bag> </class> If I return all author objects using something like the following, I will get what initially appeared to be duplicate Author records: Session.Query<Author>().List<Author>() The extra author objects are created when an author is mapped to Book objects that have IsDeleted = 1 and IsDeleted = 0. Rather than creating one Author object with an enumerable that contains only the books with IsDeleted = 0, it will create two author objects. The first author object has a Books enumerable that contains books with IsDeleted = 0. The second author object will contain an enumerable of null book objects. Similarly, if an object only has one book map, and that map points to a book with IsDeleted = 1, then an author object is returned with a Books collection having one null object. I'm thinking part of the problem stems from the map table objects linking to rows that satisfy the where condition on the bag object but do not meet the many-to-many where condition. This is happening with NHibernate version 3.0.0.4980. Is this a configuration issue or something else?

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• Conditional references in .NET project, possible to get rid of warning?

  - by Lasse V. Karlsen

  I have two references to a SQLite assembly, one for 32-bit and one for 64-bit, which looks like this (this is a test project to try to get rid of the warning, don't get hung up on the paths): <Reference Condition=" '$(Platform)' == 'x64' " Include="System.Data.SQLite, Version=1.0.61.0, Culture=neutral, PublicKeyToken=db937bc2d44ff139, processorArchitecture=AMD64"> <SpecificVersion>True</SpecificVersion> <HintPath>..\..\LVK Libraries\SQLite3\version_1.0.65.0\64-bit\System.Data.SQLite.DLL</HintPath> </Reference> <Reference Condition=" '$(Platform)' == 'x86' " Include="System.Data.SQLite, Version=1.0.65.0, Culture=neutral, PublicKeyToken=db937bc2d44ff139, processorArchitecture=x86"> <SpecificVersion>True</SpecificVersion> <HintPath>..\..\LVK Libraries\SQLite3\version_1.0.65.0\32-bit\System.Data.SQLite.DLL</HintPath> </Reference> This produces the following warning: Warning 1 The referenced component 'System.Data.SQLite' could not be found. Is it possible for me to get rid of this warning? One way I've looked at it to just configure my project to be 32-bit when I develop, and let the build machine fix the reference when building for 64-bit, but this seems a bit awkward and probably prone to errors. Any other options? The reason I want to get rid of it is that the warning is apparently being picked up by TeamCity and periodically flagged as something I need to look into, so I'd like to get completely rid of it.

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• Eliminate full table scan due to BETWEEN (and GROUP BY)

  - by Dave Jarvis

  Description According to the explain command, there is a range that is causing a query to perform a full table scan (160k rows). How do I keep the range condition and reduce the scanning? I expect the culprit to be: Y.YEAR BETWEEN 1900 AND 2009 AND Code Here is the code that has the range condition (the STATION_DISTRICT is likely superfluous). SELECT COUNT(1) as MEASUREMENTS, AVG(D.AMOUNT) as AMOUNT, Y.YEAR as YEAR, MAKEDATE(Y.YEAR,1) as AMOUNT_DATE FROM CITY C, STATION S, STATION_DISTRICT SD, YEAR_REF Y FORCE INDEX(YEAR_IDX), MONTH_REF M, DAILY D WHERE -- For a specific city ... -- C.ID = 10663 AND -- Find all the stations within a specific unit radius ... -- 6371.009 * SQRT( POW(RADIANS(C.LATITUDE_DECIMAL - S.LATITUDE_DECIMAL), 2) + (COS(RADIANS(C.LATITUDE_DECIMAL + S.LATITUDE_DECIMAL) / 2) * POW(RADIANS(C.LONGITUDE_DECIMAL - S.LONGITUDE_DECIMAL), 2)) ) <= 50 AND -- Get the station district identification for the matching station. -- S.STATION_DISTRICT_ID = SD.ID AND -- Gather all known years for that station ... -- Y.STATION_DISTRICT_ID = SD.ID AND -- The data before 1900 is shaky; insufficient after 2009. -- Y.YEAR BETWEEN 1900 AND 2009 AND -- Filtered by all known months ... -- M.YEAR_REF_ID = Y.ID AND -- Whittled down by category ... -- M.CATEGORY_ID = '003' AND -- Into the valid daily climate data. -- M.ID = D.MONTH_REF_ID AND D.DAILY_FLAG_ID <> 'M' GROUP BY Y.YEAR Update The SQL is performing a full table scan, which results in MySQL performing a "copy to tmp table", as shown here: +----+-------------+-------+--------+-----------------------------------+--------------+---------+-------------------------------+--------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+--------+-----------------------------------+--------------+---------+-------------------------------+--------+-------------+ | 1 | SIMPLE | C | const | PRIMARY | PRIMARY | 4 | const | 1 | | | 1 | SIMPLE | Y | range | YEAR_IDX | YEAR_IDX | 4 | NULL | 160422 | Using where | | 1 | SIMPLE | SD | eq_ref | PRIMARY | PRIMARY | 4 | climate.Y.STATION_DISTRICT_ID | 1 | Using index | | 1 | SIMPLE | S | eq_ref | PRIMARY | PRIMARY | 4 | climate.SD.ID | 1 | Using where | | 1 | SIMPLE | M | ref | PRIMARY,YEAR_REF_IDX,CATEGORY_IDX | YEAR_REF_IDX | 8 | climate.Y.ID | 54 | Using where | | 1 | SIMPLE | D | ref | INDEX | INDEX | 8 | climate.M.ID | 11 | Using where | +----+-------------+-------+--------+-----------------------------------+--------------+---------+-------------------------------+--------+-------------+ Related http://dev.mysql.com/doc/refman/5.0/en/how-to-avoid-table-scan.html http://dev.mysql.com/doc/refman/5.0/en/where-optimizations.html http://stackoverflow.com/questions/557425/optimize-sql-that-uses-between-clause Thank you!

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• Designing a chain of states

  - by devoured elysium

  I want to model a kind of FSM(Finite State Machine). I have a sequence of states (let's say, from StateA to StateZ). This sequence is called a Chain and is implemented internally as a List. I will add states by the order I want them to run. My purpose is to be able to make a sequence of actions in my computer (for example, mouse clicks). (I know this has been done a zillion times). So a state is defined as a: boolean Precondition() <- Checks to see if for this state, some condition is true. For example, if I want to click in the Record button of a program, in this method I would check if the program's process is running or not. If it is, go to the next state in the chain list, otherwise, go to what was defined as the fail state (generally is the first state of them all). IState GetNextState() <- Returns the next state to evaluate. If Precondition() was sucessful, it should yield the next state in the chain otherwise it should yield the fail state. Run() Simply checks the Precondition() and sets the internal data so GetNextState() works as expected. So, a naive approach to this would be something like this: Chain chain = new Chain(); //chain.AddState(new State(Precondition, FailState, NextState) <- Method structure chain.AddState(new State(new WinampIsOpenCondition(), null, new <problem here, I want to referr to a state that still wasn't defined!>); The big problem is that I want to make a reference to a State that at this point still wasn't defined. I could circumvent the problem by using strings when refrering to states and using an internal hashtable, but isn't there a clearer alternative? I could just pass only the pre-condition and failure states in the constructor, having the chain just before execution put in each state the correct next state in a public property but that seems kind of awkward.

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• PHP what is faster to use

  - by user1631500

  What is faster / better to use? To put html into variables and print them later, or to just html print / echo print the content based on condition? EXAMPLE 1:(html into variables) if(!isset($_SESSION['daddy'])) { $var = "<span class='something'>Go here:<a href='#'>Click</a></span> <span class='something'>Go here:<a href='#'>Click</a></span>" } else { $one=$_SESSION["one"]; $two=$_SESSION["two"]; $three=$_SESSION["three"]; $var = You are cool enough to view the content; } echo $var; EXAMPLE 2:(print based on condition) if(!isset($_SESSION['daddy'])) { $var = 1; } else { $one=$_SESSION["one"]; $two=$_SESSION["two"]; $three=$_SESSION["three"]; $var = 0; } if ($var==1) { ?> <span class='something'>Go here:<a href='#'>Click</a></span> <span class='something'>Go here:<a href='#'>Click</a></span <?php } else { ?> You are cool enough to view the content. <?php } ?>

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• Building Active Record Conditions in an array - private method 'scan' called error

  - by Nick

  Hi, I'm attempting to build a set of conditions dynamically using an array as suggested in the first answer here: http://stackoverflow.com/questions/1658990/one-or-more-params-in-model-find-conditions-with-ruby-on-rails. However I seem to be doing something incorrectly and I'm not sure if what I'm trying is fundamentally unsound or if I'm simply botching my syntax. I'm simplifying down to a single condition here to try to illustrate the issue as I've tried to built a simple Proof of concept along these lines before layering on the 5 different condition styles I'm contending with. This works: excluded.push 12 excluded.push 30 @allsites = Site.all(:conditions => ["id not in (?)", excluded]) This results in a private method 'scan' called error: excluded.push 12 excluded.push 30 conditionsSet << ["id not in (?)", excluded] @allsites = Site.all(:conditions => conditionsSet) Thanks for any advice. I wasn't sure if the proper thing was to put this as a followup item to the related question/answers I noted at the top. Since I've got a problem not an answer. If there is a better way to post this related to the existing post please let me know.

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• finding N contiguous zero bits in an integer to the left of the MSB from another

  - by James Morris

  First we find the MSB of the first integer, and then try to find a region of N contiguous zero bits within the second number which is to the left of the MSB from the first integer. Here is the C code for my solution: typedef unsigned int t; unsigned const t_bits = sizeof(t) * CHAR_BIT; _Bool test_fit_within_left_of_msb( unsigned width, t val1, t val2, unsigned* offset_result) { unsigned offbit = 0; unsigned msb = 0; t mask; t b; while(val1 >>= 1) ++msb; while(offbit + width < t_bits - msb) { mask = (((t)1 << width) - 1) << (t_bits - width - offbit); b = val2 & mask; if (!b) { *offset_result = offbit; return true; } if (offbit++) /* this conditional bothers me! */ b <<= offbit - 1; while(b <<= 1) offbit++; } return false; } Aside from faster ways of finding the MSB of the first integer, the commented test for a zero offbit seems a bit extraneous, but necessary to skip the highest bit of type t if it is set. I have also implemented similar algorithms but working to the right of the MSB of the first number, so they don't require this seemingly extra condition. How can I get rid of this extra condition, or even, are there far more optimal solutions?

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