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  • (type theoretical) How is ([] ==) [] typed in haskell?

    - by Ingo
    It sounds silly, but I can't get it. Why can the expression [] == [] be typed at all? More specifically, which type (in class Eq) is inferred to the type of list elements? In a ghci session, I see the following: Prelude> :t (==[]) (==[]) :: (Eq [a]) => [a] -> Bool But the constraint Eq [a] implies Eq a also, as is shown here: Prelude> (==[]) ([]::[IO ()]) <interactive>:1:1: No instance for (Eq (IO ())) arising from use of `==' at <interactive>:1:1-2 Probable fix: add an instance declaration for (Eq (IO ())) In the definition of `it': it = (== []) ([] :: [IO ()]) Thus, in []==[], the type checker must assume that the list element is some type a that is in class Eq. But which one? The type of [] is just [a], and this is certainly more general than Eq a = [a].

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  • Related objects in reportingviewer 10.0.0.0 give #error

    - by Bart-Jan Poirot
    In my VB.net apps i make use of Linq2SQL and Reportviewer with RDLC reports. With Visual Studio 2010 they upgraded this reportviewer component so you can use the newer RDL specification from 2008. Now I've a problem to show related objects. For example assume you provide an order to the datasource of the report and then you can show something like Fields!Customer.Value.Name where Customer is a related entity. I also got the error in my immediate window: *Warning: The Value expression for the textrun ‘Name_1.Paragraphs[0].TextRuns[0]’ contains an error: The specified operation is not valid. (rsRuntimeErrorInExpression)*

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  • How to regex match a string of alnums and hyphens, but which doesn't begin or end with a hyphen?

    - by Shahar Evron
    I have some code validating a string of 1 to 32 characters, which may contain only alpha-numerics and hyphens ('-') but may not begin or end with a hyphen. I'm using PCRE regular expressions & PHP (albeit the PHP part is not really important in this case). Right now the pseudo-code looks like this: if (match("/^[\p{L}0-9][\p{L}0-9-]{0,31}$/u", string) and not match("/-$/", string)) print "success!" That is, I'm checking first that the string is of right contents, doesn't being with a '-' and is of the right length, and then I'm running another test to see that it doesn't end with a '-'. Any suggestions on merging this into a single PCRE regular expression? I've tried using look-ahead / look-behind assertions but couldn't get it to work.

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  • Double-Escaped Unicode Javascript Issue

    - by Jeffrey Winter
    I am having a problem displaying a Javascript string with embedded Unicode character escape sequences (\uXXXX) where the initial "\" character is itself escaped as "&#92;" What do I need to do to transform the string so that it properly evaluates the escape sequences and produces output with the correct Unicode character? For example, I am dealing with input such as: "this is a &#92;u201ctest&#92;u201d"; attempting to decode the "&#92;" using a regex expression, e.g.: var out = text.replace('/&#92;/g','\'); results in the output text: "this is a \u201ctest\u201d"; that is, the Unicode escape sequences are displayed as actual escape sequences, not the double quote characters I would like.

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  • Check for default value of attribute in XPath

    - by iref
    Hi, i have XML schema: <xsd:complexType name="contactsType"> <xsd:sequence> <xsd:element name="contact" type="contactType" minOccurs="0" maxOccurs="unbounded"/> </xsd:sequence> <xsd:attribute name="visible" type="xsd:boolean" default="true"/> </xsd:complexType> and i want to find all contacts which have @visible=true, //contacts[@visible='true'] but this expression doesn' t return nodes without set @visible like this: <contacts /> so i want to know if there is any function in XPath which returns also default values of attributes Thanks Jan

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  • Copy constructor demo (crashing... case 2)

    - by AKN
    Please have a glance at this program: class CopyCon { public: char *name; CopyCon() { name = new char[20]; name = "Hai";//_tcscpy(name,"Hai"); } CopyCon(const CopyCon &objCopyCon) { name = new char[_tcslen(objCopyCon.name)+1]; _tcscpy(name,objCopyCon.name); } ~CopyCon() { if( name != NULL ) { delete[] name; name = NULL; } } }; int main() { CopyCon obj1; CopyCon obj2(obj1); cout<<obj1.name<<endl; cout<<obj2.name<<endl; } This program crashes on execution. Error: "Expression: _BLOCK_TYPE_IS_VALID(pHead-nBlockUse)" If I assign "Hai" to name using aasignment operator, its crashing. Where as when I use string func _tcscpy to assign "Hai" to name, its working perfectly. Can some one explain why so?

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  • What is lifetime of lambda-derived implicit functors in C++ ?

    - by Fyodor Soikin
    The question is simple: what is lifetime of that functor object that is automatically generated for me by the C++ compiler when I write a lambda-expression? I did a quick search, but couldn't find a satisfactory answer. In particular, if I pass the lambda somewhere, and it gets remembered there, and then I go out of scope, what's going to happen once my lambda is called later and tries to access my stack-allocated, but no longer alive, captured variables? Or does the compiler prevent such situation in some way? Or what?

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  • Perl Regex Multiple Items in Single String

    - by Sho Minamimoto
    I'm trying to parse a single string and get multiple chunks of data out from the same string with the same regex conditions. I'm parsing a single HTML doc that is static (For an undisclosed reason, I can't use an HTML parser to do the job.) I have an expression that looks like $string =~ /\<img\ssrc\="(.*)"/; and I want to get the value of $1. However, in the one string, there are many img tags like this, so I need something like an array returned (@1?) is this possible?

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  • What logic operator to use, as3?

    - by VideoDnd
    What operator or expression can I use that will fire on every number, including zero? I want a logic operator that will fire with ever number it receives. My animations pause at zero. This skips on zero if (numberThing> 0); This skips on 9 if (numberThing>> 0); This jitters 'fires quickly and goes back on count' if (numberThing== 0); EXPLANATION I'm catching split string values in a logic function, and feeding them to a series of IF, ELSE IF statements. I'm using this with a timer, so I can measure the discrepency. CODE • I GET VALUES FROM TIMER • STRING GOES TO TEXTFIELD 'substr' • NUMBER TRIGGERS TWEENS 'parseInt' • Goes to series of IF and ELSE IF statements

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  • What's the official Microsoft way to track counts of dynamic controls to be reconstructed upon Postback?

    - by John K
    When creating dynamic controls based on a data source of arbitrary and changing size, what is the official way to track exactly how many controls need to be rebuilt into the page's control collection after a Postback operation (i.e. on the server side during the ASP.NET page event lifecycle) specifically the point at which dynamic controls are supposed to be rebuilt? Where is the arity stored for retrieval and reconstruction usage? By "official" I mean the Microsoft way of doing it. There exist hacks like Session storage, etc but I want to know the bonafide or at least Microsoft-recommended way. I've been unable to find a documentation page stating this information. Usually code samples work with a set of dynamic controls of known numbers. It's as if doing otherwise would be tougher. Update: I'm not inquiring about user controls or static expression of declarative controls, but instead about dynamically injecting controls completely from code-behind, whether they be mine, 3rd-party or built-in ASP.NET controls.

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  • How do you fix the Silverlight application shift that occurs in the Firefox browser?

    - by Roy
    Hi, Currently I have an Silverlight application that when run on Firefox browser (ver 3.6) the entire contents of the Silverlight application shifts a little, and also the scrollbars on both the bottom and the side appear when I first use it. This does not happen in IE 8. How can I fix this in Firefox so it doesn't happen? The project type I created was the "Silverlight 3 Application + Website" via Expression Blend 3. This the code I am using in my MainPage.xaml: <UserControl xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" x:Class="StackoverflowExample.MainPage" Width="640" Height="480"> <Grid x:Name="LayoutRoot" Background="Green"> <Rectangle Fill="#FFBB2020" Stroke="Black" Margin="155,58,266,178"/> <Button Margin="199,180,302,236" Content="Button"/> </Grid> </UserControl>

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  • Why does gcc think that I am trying to make a function call in my template function signature?

    - by nieldw
    GCC seem to think that I am trying to make a function call in my template function signature. Can anyone please tell me what is wrong with the following? 227 template<class edgeDecor, class vertexDecor, bool dir> 228 vector<Vertex<edgeDecor,vertexDecor,dir>> Graph<edgeDecor,vertexDecor,dir>::vertices() 229 { 230 return V; 231 }; GCC is giving the following: graph.h:228: error: a function call cannot appear in a constant-expression graph.h:228: error: template argument 3 is invalid graph.h:228: error: template argument 1 is invalid graph.h:228: error: template argument 2 is invalid graph.h:229: error: expected unqualified-id before ‘{’ token Thanks a lot.

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  • Using DateDiff in Entity Framwork on a SQL CE database

    - by deverop
    I have a method which should return a list of anonymous objects with a calculated column like this: var tomorrow = DateTime.Today.AddDays(1); return from t in this.Events where (t.StartTime >= DateTime.Today && t.StartTime < tomorrow && t.EndTime.HasValue) select new { Client = t.Activity.Project.Customer.Name, Project = t.Activity.Project.Name, Task = t.Activity.Task.Name, Rate = t.Activity.Rate.Name, StartTime = t.StartTime, EndTime = t.EndTime.Value, Hours = (System.Data.Objects.SqlClient.SqlFunctions.DateDiff("m", t.StartTime, t.EndTime.Value) / 60), Description = t.Activity.Description }; Unfortunately I get the following error from the DateDiff function: The specified method 'System.Nullable1[System.Int32] DateDiff(System.String, System.Nullable1[System.DateTime], System.Nullable`1[System.DateTime])' on the type 'System.Data.Objects.SqlClient.SqlFunctions' cannot be translated into a LINQ to Entities store expression. Any ideas what I could have done wrong here? EDIT: I also tried the EntityFunctions class mentioned here, but that did not work as well. Minutes = EntityFunctions.DiffMinutes(t.EndTime, t.StartTime),

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  • preg_match problem

    - by Biroka
    I'm trying to get some stuff from a string in php. In RegexBuddy and Regular expression tester (firefox addon) it works good, but php gives me the following: Warning: preg_match() [function.preg-match]: Compilation failed: unmatched parentheses at offset 34 in D:\path\example.php on line 62 my pattern is "/.{4}_tmp\\([A-Za-z0-9.\\]*)\(([0-9]*)\) : (.*)/i" an example string: C:\Temp\browseide\projects\32\821C_tmp\SourceFiles\main.c(8) : error C2143: syntax error : missing ';' before 'for' what RegexBuddy gets: 821C_tmp\SourceFiles\main.c(8) : error C2143: syntax error : missing ';' before 'for' Group 1: SourceFiles\main.c Group 2: 8 Group 3: error C2143: syntax error : missing ';' before 'for'

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  • Mixed Table Type with other types as parameters to Stored Procedured c#

    - by amemak
    Hi, I am asking about how could i pass multi parameters to a stored procedure, one of these parameters is user defined table. When I tried to do it it shows this error: INSERT INTO BD (ID, VALUE, BID) values( (SELECT t1.ID, t1.Value FROM @Table AS t1),someintvalue) here @Table is the user defined table parameter. Msg 116, Level 16, State 1, Procedure UpdateBD, Line 12 Only one expression can be specified in the select list when the subquery is not introduced with EXISTS. Msg 109, Level 15, State 1, Procedure UpdateBD, Line 11 There are more columns in the INSERT statement than values specified in the VALUES clause. The number of values in the VALUES clause must match the number of columns specified in the INSERT statement. Thank you

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  • SImplifying with LINQ - Basic selection

    - by baron
    Hello foreach (var person in peopleList.Where(person => person.FirstName == "Messi")) { selectPeople.Add(person); } I am just wondering if there is any way to simplify this using LINQ. Like rather than look at all the people I was trying to use LINQ to just fill a list with the "Messi"'s... was trying something like... var selectPeople = peopleList.Select(x=>x.FirstName=="Messi"); Then I could just add everyone in that list without a check. But it doesn't quite work as planned. Maybe there's no point simplifying that expression. But the question seemed worthwhile just to strengthen my LINQ knowledge.

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  • How do I create regex groups for replacement?

    - by resting
    I have this sample string: Image: SGD$45.32 SKU: 3f3f3 dfdfd grg4t BP 6yhf Pack Size: 1000's Color: Green Price: SGD$45.32 SGD$45... I would like to remove all the prices namely: SGD$45.32 Price: SGD$45.32 SGD$45 I have this expression thats supposed to match the 3 groups: $pattern = '/(Price.+\sSGD\$\d+\.\d{2})(SGD\$\d+\.\d{2})(SGD\$\d+)/'; $new_snippet = preg_replace($pattern, '', $snippet);` But apparently its not working. It works if I replace a single group at a time. But, I'd like to know if it possible to replace all possible matching groups with a single statement. Tried preg_match_all($pattern, $snippet, $matches); to show matches based on the above pattern, but no matches are found if I put all 3 groups together.

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  • Jasper Reports - Add one day to a Date Parameter

    - by Templar
    I'm creating a Jasper report that includes the following parameters: DATESTART (Date) DATEEND (Date) These parameters indicate a date range for a field called DATECREATED (Timestamp) which includes times. I would like the date range to be INCLUSIVE, that is, if I filter for "Jan 1, 2009" to "Jan 31, 2009", any DATECREATED value on Jan 31, 2009 (such as "Jan 31, 2009 15:00") will be included in the report. When I used Crystal Reports in the past, I used the DATEADD function to create a filter expression like the following: {DATECREATED} >= {DATESTART} and {DATECREATED} < DATEADD("d", 1, {DATEEND}) (I realize that this isn't syntactically correct, but you get the idea.) Is there any way to do something similar in Jasper Reports?

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  • SQL CHECK constraint issues

    - by blahblah
    I'm using SQL Server 2008 and I have a table with three columns: Length, StartTime and EndTime. I want to make a CHECK constraint on this table which says that: if Length == NULL then StartTime <> NULL and EndTime <> NULL else StartTime == NULL and EndTime == NULL I've begun to try things like this: Length == NULL AND StartTime <> NULL AND EndTime <> NULL Obviously this is not enough, but even this simple expression will not validate. I get the error: "Error validating 'CK_Test_Length_Or_Time'. Do you want to edit the constraint?" Any ideas on how to go about doing this?

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  • Error: A SQLParamenter wtih ParameterName @myparm is not contained by this SQLParameter Collection

    - by SidC
    Good Morning, I'm working on an ASP.NET 3.5 webforms application and have written the following code: Protected Sub btnSubmit_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnSubmit.Click Dim connectionString As String = WebConfigurationManager.ConnectionStrings("Diel_inventoryConnectionString").ConnectionString Dim con As New SqlConnection(connectionString) Dim adapter1 As New SqlDataAdapter adapter1.SelectCommand = New SqlCommand adapter1.SelectCommand.CommandType = CommandType.StoredProcedure adapter1.SelectCommand.CommandText = "PartSproc" Dim parmNSN As New SqlParameter("@NSN", SqlDbType.NVarChar) Dim parmName As New SqlParameter("@PartName", SqlDbType.NVarChar) txtNSN.Text = adapter1.SelectCommand.Parameters("@NSN").Value txtSearch.Text = adapter1.SelectCommand.Parameters("@PartName").Value Dim dt As New DataTable() adapter1.Fill(dt) MySearch.DataSource = dt MySearch.DataBind() End Sub When I run the page, I receive the error A SQLParameter with @NSN is not contained by this SQLParameter Collection. I tried using apostrophes around the @NSN and @PartName but that does not work either and presents expression expected error. How might I rectify the above code so that it references the @NSN and @PartName parameters correctly? Thanks, Sid

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  • Numbering Regex Submatches

    - by gentlylisped
    Is there a canonical ordering of submatch expressions in a regular expression? For example: What is the order of the submatches in "(([0-9]{3}).([0-9]{3}).([0-9]{3}).([0-9]{3}))\s+([A-Z]+)" ? a. (([0-9]{3})\.([0-9]{3})\.([0-9]{3})\.([0-9]{3}))\s+([A-Z]+) (([0-9]{3})\.([0-9]{3})\.([0-9]{3})\.([0-9]{3})) ([A-Z]+) ([0-9]{3}) ([0-9]{3}) ([0-9]{3}) ([0-9]{3}) b. (([0-9]{3})\.([0-9]{3})\.([0-9]{3})\.([0-9]{3}))\s+([A-Z]+) (([0-9]{3})\.([0-9]{3})\.([0-9]{3})\.([0-9]{3})) ([0-9]{3}) ([0-9]{3}) ([0-9]{3}) ([0-9]{3}) ([A-Z]+) or c. somthin' else.

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  • regex to format a float in php

    - by Itamar Bar-Lev
    I have a PHP function for formatting a float to a given amount of decimal points that uses number_format(), and then removes the unneeded zeros (and also the '.' if possible): $float = number_format($float, $decimalPlaces, '.', ''); for ($i = 0; $i < $decimalPlaces; $i++) { if (substr($float, strlen($float) - 1, strlen($float)) == '0') { $float = substr($float, 0, strlen($float) - 1); } } if (substr($float, strlen($float) - 1, strlen($float)) == '.') { $float = substr($float, 0, strlen($float) - 1); } Is it possible to do so more effectively with a regular expression?

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  • In Haskell, how can you sort a list of infinite lists of strings?

    - by HaskellNoob
    So basically, if I have a (finite or infinite) list of (finite or infinite) lists of strings, is it possible to sort the list by length first and then by lexicographic order, excluding duplicates? A sample input/output would be: Input: [["a", "b",...], ["a", "aa", "aaa"], ["b", "bb", "bbb",...], ...] Output: ["a", "b", "aa", "bb", "aaa", "bbb", ...] I know that the input list is not a valid haskell expression but suppose that there is an input like that. I tried using merge algorithm but it tends to hang on the inputs that I give it. Can somebody explain and show a decent sorting function that can do this? If there isn't any function like that, can you explain why? In case somebody didn't understand what I meant by the sorting order, I meant that shortest length strings are sorted first AND if one or more strings are of same length then they are sorted using < operator. Thanks!

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  • Using Regex groups in bash

    - by AlexeyMK
    Greetings, I've got a directory with a list of pdfs in it: file1.pdf, file2.pdf, morestuff.pdf ... etc. I want to convert these pdfs to pngs, ie file1.png, file2.png, morestuff.png ... etc. The basic command is, convert from to, But I'm having trouble getting convert to rename to the same file name. The obvious 'I wish it worked this way' is convert *.pdf *.png But clearly that doesn't work. My thought process is that I should utilize regular expression grouping here, to say somethink like convert (*).pdf %1.png but that clearly isn't the right syntax. I'm wondering what the correct syntax is, and whether there's a better approach (that doesn't require jumping into perl or python) that I'm ignoring. Thanks!

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  • Do I need to include the 'this' when using a property name in a closure?

    - by Scott Whitlock
    I'm using a list of Actions to store an undo history for an object. Let's say I have a property of my object called myChildObject and it's being changed, so I want to store the undo action where I would set it back to it's current value: public class Class1 { public Class1() { } private readonly List<Action> m_undoActions = new List<Action>(); private SomeObject myChildObject { get; set; } public void ChangeState(SomeObject newChildObject) { // copies the reference SomeObject existingObject = myChildObject; m_undoActions.Add(() => myChildObject = existingObject); myChildObject = newChildObject; } } Looking at the lambda expression, existingObject is a local variable, so it's using a closure to pass a reference to that variable, but what about the property myChildObject? Do I need to use 'this' to preface it? Do I need to make a copy of the 'this' reference to a local variable first? Thanks for helping me understand this closure stuff.

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