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• When is a bool not a bool (compiler warning C4800)

  - by omatai

  Consider this being compiled in MS Visual Studio 2005 (and probably others): CPoint point1( 1, 2 ); CPoint point2( 3, 4 ); const bool point1And2Identical( point1 == point2 ); // C4800 warning const bool point1And2TheSame( ( point1 == point2 ) == TRUE ); // no warning What the...? Is the MSVC compiler brain-dead? As far as I can tell, TRUE is #defined as 1, without any type information. So by what magic is there any difference between these two lines? Surely the type of the expression inside the brackets is the same in both cases? [This part of the question now satisfactorily answered in the comments just below] Personally, I think that avoiding the warning by using the == TRUE option is ugly (though less ugly than the != 0 alternative, despite being more strictly correct), and it is better to use #pragma warning( disable:4800 ) to imply "my code is good, the compiler is an ass". Agree? Note - I have seen all manner of discussion on C4800 talking about assigning ints to bools, or casting a burger combo with large fries (hold the onions) to a bool, and wondering why there are strange results. I can't find a clear answer on what seems like a much simpler question... that might just shine line on C4800 in general.

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• Using the JPA Criteria API, can you do a fetch join that results in only one join?

  - by Shaun

  Using JPA 2.0. It seems that by default (no explicit fetch), @OneToOne(fetch = FetchType.EAGER) fields are fetched in 1 + N queries, where N is the number of results containing an Entity that defines the relationship to a distinct related entity. Using the Criteria API, I might try to avoid that as follows: CriteriaBuilder builder = entityManager.getCriteriaBuilder(); CriteriaQuery<MyEntity> query = builder.createQuery(MyEntity.class); Root<MyEntity> root = query.from(MyEntity.class); Join<MyEntity, RelatedEntity> join = root.join("relatedEntity"); root.fetch("relatedEntity"); query.select(root).where(builder.equals(join.get("id"), 3)); The above should ideally be equivalent to the following: SELECT m FROM MyEntity m JOIN FETCH myEntity.relatedEntity r WHERE r.id = 3 However, the criteria query results in the root table needlessly being joined to the related entity table twice; once for the fetch, and once for the where predicate. The resulting SQL looks something like this: SELECT myentity.id, myentity.attribute, relatedentity2.id, relatedentity2.attribute FROM my_entity myentity INNER JOIN related_entity relatedentity1 ON myentity.related_id = relatedentity1.id INNER JOIN related_entity relatedentity2 ON myentity.related_id = relatedentity2.id WHERE relatedentity1.id = 3 Alas, if I only do the fetch, then I don't have an expression to use in the where clause. Am I missing something, or is this a limitation of the Criteria API? If it's the latter, is this being remedied in JPA 2.1 or are there any vendor-specific enhancements? Otherwise, it seems better to just give up compile-time type checking (I realize my example doesn't use the metamodel) and use dynamic JPQL TypedQueries.

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• CodeModel help needed for right-hand singleton.getinstance() assignment.

  - by antarti

  I've been able to generate 99% of what I need with the CodeModel API, but I am stumped here... Using the various "directXX" methods does not add import statements to the generated code, and I can work without the "directXXX" type of methods except for one place in a generated class. Suppose I desire a generated method like: /** * Copies data from this Value-Obj instance, to the returned PERSON instance. * * @return PERSON * */ public PERSON mapVOToPERSON() throws MappingException { Mapper mapper = (com.blah.util.MapperSingleton.getMapperInstance()); return mapper.map(this, PERSON.class); } You can see the right hand of the Mapper assignment in parens. Emitting the entire package+class was the only way I could find to just declare "SomeSingleton.someMethod()" on the right hand side and have the generated code compile. Without the MapperSingleton being added to the object model, there is no import generated... Questions: 1) Is there a way to force an import to be generated? 2) How to declare an expression that gives me the right side of the Mapper assignment within the object model (so that an import of MapperSingleton gets generated. Any help appreciated...

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• help date format in vb.net

  - by bachchan

  Dim Con As OleDb.OleDbConnection Dim Sql As String = Nothing Dim Reader As OleDb.OleDbDataReader Dim ComboRow As Integer = -1 Dim Columns As Integer = 0 Dim Category As String = Nothing Dim oDatumMin As Date Dim column As String column = Replace(TxtDateMax.Text, "'", "''") 'oDatumMin = Convert.ToDateTime(TxtDateMin.Text) oDatumMin = DtpMin.Value Dim oPath As String oPath = Application.StartupPath ' Select records. Con = New OleDb.OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" & oPath & "\trb.accdb;") Dim cmd As New OleDb.OleDbCommand 'Dim data_reader As OleDbDataReader = cmd.ExecuteReader() Sql = ("SELECT * FROM " & cmbvalue & " WHERE Datum>='" & oDatumMin & "'") cmd = New OleDb.OleDbCommand(Sql, Con) Con.Open() Reader = cmd.ExecuteReader() Do While Reader.Read() Dim new_item As New ListViewItem(Reader.Item("Datum").ToString) new_item.SubItems.Add(Reader.Item("Steleks i krpe za cišcenje-toal papir-ubrusi-domestos").ToString) new_item.SubItems.Add(Reader.Item("TEKUCINA ZA CIŠCENJE PLOCICA").ToString) new_item.SubItems.Add(Reader.Item("KESE ZA SMECE").ToString) new_item.SubItems.Add(Reader.Item("OSTALO-džoger-spužva za laminat").ToString) new_item.SubItems.Add(Reader.Item("PAPIR").ToString) LvIzvjestaj.Items.Add(new_item) Loop ' Close the connection.strong text Con.Close()`` when i select table,(cmbvalue) from combobox and when i select date from datetime picker (dtp) or in last case from texbox converted to date and time sql looks like this "SELECT * FROM Uprava WHERE Datum='2.6.2010 10:28:14'" and all query looks ok but am geting Data type mismatch in criteria expression. error for date (oDatumMin) when excute column in access is also set to date i have no idea what else to try

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• Performance of stored proc when updating columns selectively based on parameters?

  - by kprobst

  I'm trying to figure out if this is relatively well-performing T-SQL (this is SQL Server 2008). I need to create a stored procedure that updates a table. The proc accepts as many parameters as there are columns in the table, and with the exception of the PK column, they all default to NULL. The body of the procedure looks like this: CREATE PROCEDURE proc_repo_update @object_id bigint ,@object_name varchar(50) = NULL ,@object_type char(2) = NULL ,@object_weight int = NULL ,@owner_id int = NULL -- ...etc AS BEGIN update object_repo set object_name = ISNULL(@object_name, object_name) ,object_type = ISNULL(@object_type, object_type) ,object_weight = ISNULL(@object_weight, object_weight) ,owner_id = ISNULL(@owner_id, owner_id) -- ...etc where object_id = @object_id return @@ROWCOUNT END So basically: Update a column only if its corresponding parameter was provided, and leave the rest alone. This works well enough, but as the ISNULL call will return the value of the column if the received parameter was null, will SQL Server optimize this somehow? This might be a performance bottleneck on the application where the table might be updated heavily (insertion will be uncommon so the performance there is not a problem). So I'm trying to figure out what's the best way to do this. Is there a way to condition the column expressions with something like CASE WHEN or something? The table will be indexed up the wazoo as well for read performance. Is this the best approach? My alternative at this point is to create the UPDATE expression in code (e.g. inline SQL) and execute it against the server. This would solve my doubts about performance, but I'd rather leave this in a stored proc if possible.

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• Array's index and argc signedness

  - by tusbar

  Hello, The C standard (5.1.2.2.1 Program startup) says: The function called at program startup is named main. [...] It shall be de?ned with a return type of int and with no parameters: int main(void) { /* ... */ } or with two parameters [...] : int main(int argc, char *argv[]) { /* ... */ } And later says: The value of argc shall be nonnegative. Why shouldn't argc be defined as an unsigned int, argc supposedly meaning 'argument count'? Should argc be used as an index for argv? So I started wondering if the C standard says something about the type of array's index. Is it signed? 6.5.2.1 Array subscripting: One of the expressions shall have type ‘‘pointer to object type’’, the other expression shall have integer type, and the result has type ‘‘type’’. It doesn't say anything about its signedness (or I didn't find it). It is pretty common to see codes using negatives array indexes (array[-1]) but isn't it undefined behavior? Should array's indexes be unsigned?

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• how do i make the app take correct input..?

  - by user1824343

  This is my windows app's one layout which converts Celsius to Fahrenheit. The problem is that when I try to input the temperature it shows some junk(for eg: if i enter '3' it displayin '3.0000009') and sometimes its even showing stack overflow exception. The output is also not shown properly : cel.text is the textbox for celsius. fahre.text is the textbox for fahrenheit. namespace PanoramaApp1 { public partial class FahretoCel : PhoneApplicationPage { public FahretoCel() { InitializeComponent(); } private void fahre_TextChanged(object sender, TextChangedEventArgs e) { if (fahre.Text != "") { try { double F = Convert.ToDouble(fahre.Text); cel.Text = "" + ((5.0/9.0) * (F - 32)) ; //this is conversion expression } catch (FormatException) { fahre.Text = ""; cel.Text = ""; } } else { cel.Text = ""; } } private void cel_TextChanged(object sender, TextChangedEventArgs e) { if (cel.Text != "") { try { Double c = Convert.ToDouble(cel.Text); fahre.Text = "" + ((c *(9.0 / 5.0 )) + 32); } catch (FormatException) { fahre.Text = ""; cel.Text = ""; } } else { fahre.Text = ""; } } } }

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• In Silverlight, what structures, aside of the ListBox, can be used for binding?

  - by Aidenn

  I need to simply provide the content of a property to a custom User Control in Silverlight. My control is something like this: <UserControl x:Class="SilverlightApplication.Header" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" mc:Ignorable="d" d:DesignWidth="300" d:DesignHeight="120"> <Grid x:Name="Header_Layout"> <StackPanel x:Name="hiHeaderContent" Width="Auto" Margin="73,8,8,8"> <TextBlock x:Name="User:" Text="{Binding name}" /> </StackPanel> </Grid> I try to use this User Control from another control where I try to pass the parameter "name" to the previous UserControl ("Header"). I don't need to create a "ListBox" as I will only have 1 header, so I try to avoid doing: <ListBox x:Name="HeaderListBox" Grid.Row="0"> <ListBox.ItemTemplate> <DataTemplate> <SilverlightApplication:Header/> </DataTemplate> </ListBox.ItemTemplate> </ListBox> in order to send the "User" account using: HeaderListBox.ItemsSource = name; Is there any other structure I can use instead of the ListBox to pass the parameter just once? It won't be a list, it's just a header... Thank you!

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• How does Haskell do pattern matching without us defining an Eq on our data types?

  - by devoured elysium

  I have defined a binary tree: data Tree = Null | Node Tree Int Tree and have implemented a function that'll yield the sum of the values of all its nodes: sumOfValues :: Tree -> Int sumOfValues Null = 0 sumOfValues (Node Null v Null) = v sumOfValues (Node Null v t2) = v + (sumOfValues t2) sumOfValues (Node t1 v Null) = v + (sumOfValues t1) sumOfValues (Node t1 v t2) = v + (sumOfValues t1) + (sumOfValues t2) It works as expected. I had the idea of also trying to implement it using guards: sumOfValues2 :: Tree -> Int sumOfValues2 Null = 0 sumOfValues2 (Node t1 v t2) | t1 == Null && t2 == Null = v | t1 == Null = v + (sumOfValues2 t2) | t2 == Null = v + (sumOfValues2 t1) | otherwise = v + (sumOfValues2 t1) + (sumOfValues2 t2) but this one doesn't work because I haven't implemented Eq, I believe: No instance for (Eq Tree) arising from a use of `==' at zzz3.hs:13:3-12 Possible fix: add an instance declaration for (Eq Tree) In the first argument of `(&&)', namely `t1 == Null' In the expression: t1 == Null && t2 == Null In a stmt of a pattern guard for the definition of `sumOfValues2': t1 == Null && t2 == Null The question that has to be made, then, is how can Haskell make pattern matching without knowing when a passed argument matches, without resorting to Eq?

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• How do I define a monadic function to work on a list in J?

  - by Gregory Higley

  Let's say I have the following J expression: # 3 ((|=0:)#]) 1+i.1000 This counts the number of numbers between 1 and 1000 that are evenly divisible by 3. (Now, before anyone points out that there's an easier way to do this, this question is about the syntax of J, and not mathematics.) Let's say I define a monadic function for this, as follows: f =: monad define # y ((|=0:)#]) 1+i.1000 ) This works great with a single argument, e.g., f 4 250 If I pass a list in, I get a length error: f 1 2 3 |length error: f Now, I completely understand why I get the length error. When you substitute the list 1 2 3 for the y argument of the monad, you get: # 1 2 3 ((|=0:)#]) 1+i.1000 If you know anything about J, it's pretty clear why the length error is occurring. So, I don't need an explanation of that. I want to define the function such that when I pass a list, it returns a list, e.g., f 1 2 3 1000 500 333 How can I either (a) redefine this function to take a list and return a list or (b) get the function to work on a list as-is without being redefined, perhaps using some adverb or other technique?

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• Why is T() = T() allowed?

  - by Rimo

  I believe the expression T() creates an rvalue (by the Standard). However, the following code compiles (at least on gcc4.0): class T {}; int main() { T() = T(); } I know technically this is possible because member functions can be invoked on temporaries and the above is just invoking the operator= on the rvalue temporary created from the first T(). But conceptually this is like assigning a new value to an rvalue. Is there a good reason why this is allowed? Edit: The reason I find this odd is it's strictly forbidden on built-in types yet allowed on user-defined types. For example, int(2) = int(3) won't compile because that is an "invalid lvalue in assignment". So I guess the real question is, was this somewhat inconsistent behavior built into the language for a reason? Or is it there for some historical reason? (E.g it would be conceptually more sound to allow only const member functions to be invoked on rvalue expressions, but that cannot be done because that might break some existing code.)

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• How to remove words based on a word count

  - by Chris

  Here is what I'm trying to accomplish. I have an object coming back from the database with a string description. This description can be up to 1000 characters long, but we only want to display a short view of this. So I coded up the following, but I'm having trouble in actually removing the number of words after the regular expression finds the total count of words. Does anyone have good way of dispalying the words which are less than the Regex.Matches? Thanks! if (!string.IsNullOrEmpty(myObject.Description)) { string original = myObject.Description; MatchCollection wordColl = Regex.Matches(original, @"[\S]+"); if (wordColl.Count < 70) // 70 words? { uxDescriptionDisplay.Text = string.Format("<p>{0}</p>", myObject.Description); } else { string shortendText = original.Remove(200); // 200 characters? uxDescriptionDisplay.Text = string.Format("<p>{0}</p>", shortendText); } }

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• Extract information from a Func<bool, T> or alike lambda

  - by Syska

  I''m trying to build a generic cache layer. ICacheRepository Say I have the following: public class Person { public int PersonId { get; set; } public string Firstname { get; set; } public string Lastname { get; set; } public DateTime Added { get; set; } } And I have something like this: list.Where(x => x.Firstname == "Syska"); Here I want to extract the above information, to see if the query supplied the "PersonId" which it did not, so I dont want to cache it. But lets say I run a query like this: list.Where(x => x.PersonId == 10); Since PersonId is my key ... I want to cache it. with the key like "Person_10" and I later can fetch it from the cache. I know its possible to extract the information with Expression<Func<>> but there seems to be a big overhead of doing this (when running compile and extract the Constant values etc. and a bunch of cache to be sure to parse right) Are there a framework for this? Or some smart/golden way of doing this ?

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• NSRegularExpression for stripping HTML Tag

  - by Prazi

  I am developing a ebook reader app. I have the .ePUB file for the entire ebook where in each topic of the ebook is a html file. I want to implement the search functionality in the app. I am using NSRegularExpression class for searching. Please consider the following html code: <temp> I am temp in tempo with temptation </temp> Say for example in the above html code I just want to search for the word temp. Now in above code temp is appearing 5 times - <temp> </temp> temp tempo temptation. I am looking for a regular expression where I can only extract the whole word "temp". I don't want to consider the word temp in the html tags <temp> </temp>. I also don't want the word tempo and temptation to be considered. Thanks in advance

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• page variable in a repeater

  - by carrot_programmer_3

  Hi I'm having a bit of an issue with a asp.net repeater I'm building a categories carousel with the dynamic categories being output by a repeater. Each item is a LinkButton control that passes an argument of the category id to the onItemClick handler. a page variable is set by this handler to track what the selected category id is.... public String SelectedID { get { object o = this.ViewState["_SelectedID"]; if (o == null) return "-1"; else return (String)o; } set { this.ViewState["_SelectedID"] = value; } } problem is that i cant seem to read this value while iterating through the repeater as follows... <asp:Repeater ID="categoriesCarouselRepeater" runat="server" onitemcommand="categoriesCarouselRepeater_ItemCommand"> <ItemTemplate> <%#Convert.ToInt32(Eval("CategoryID")) == Convert.ToInt32(SelectedID) ? "<div class=\"selectedcategory\">":"<div>"%> <asp:LinkButton ID="LinkButton1" CommandName="select_category" CommandArgument='<%#Eval("CategoryID")%>' runat="server"><img src="<%#Eval("imageSource")%>" alt="category" /><br /> </div> </ItemTemplate> </asp:Repeater> calling <%=SelectedID%> in the item template works but when i try the following expression the value of SelectedID returns empty.. <%#Convert.ToInt32(Eval("CategoryID")) == Convert.ToInt32(SelectedID) ? "match" : "not a match"%> the value is being set as follows... protected void categoriesCarouselRepeater_ItemCommand(object source, RepeaterCommandEventArgs e) { SelectedID = e.CommandArgument); } Any ideas whats wrong here?

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• lambda expressions in VB.NET... what am I doing wrong???

  - by Bob

  when I run this C# code, no problems... but when I translate it into VB.NET it compiles but blows due to 'CompareString' member not being allowed in the expression... I feel like I'm missing something key here... private void PrintButton_Click(object sender, EventArgs e) { if (ListsListBox.SelectedIndex > -1) { //Context using (ClientOM.ClientContext ctx = new ClientOM.ClientContext(UrlTextBox.Text)) { //Get selected list string listTitle = ListsListBox.SelectedItem.ToString(); ClientOM.Web site = ctx.Web; ctx.Load(site, s => s.Lists.Where(l => l.Title == listTitle)); ctx.ExecuteQuery(); ClientOM.List list = site.Lists[0]; //Get fields for this list ctx.Load(list, l => l.Fields.Where(f => f.Hidden == false && (f.CanBeDeleted == true || f.InternalName == "Title"))); ctx.ExecuteQuery(); //Get items for the list ClientOM.ListItemCollection listItems = list.GetItems( ClientOM.CamlQuery.CreateAllItemsQuery()); ctx.Load(listItems); ctx.ExecuteQuery(); // DOCUMENT CREATION CODE GOES HERE } MessageBox.Show("Document Created!"); } } but in VB.NET code this errors due to not being allowed 'CompareString' members in the ctx.Load() methods... Private Sub PrintButton_Click(sender As Object, e As EventArgs) If ListsListBox.SelectedIndex > -1 Then 'Context Using ctx As New ClientOM.ClientContext(UrlTextBox.Text) 'Get selected list Dim listTitle As String = ListsListBox.SelectedItem.ToString() Dim site As ClientOM.Web = ctx.Web ctx.Load(site, Function(s) s.Lists.Where(Function(l) l.Title = listTitle)) ctx.ExecuteQuery() Dim list As ClientOM.List = site.Lists(0) 'Get fields for this list ctx.Load(list, Function(l) l.Fields.Where(Function(f) f.Hidden = False AndAlso (f.CanBeDeleted = True OrElse f.InternalName = "Title"))) ctx.ExecuteQuery() 'Get items for the list Dim listItems As ClientOM.ListItemCollection = list.GetItems(ClientOM.CamlQuery.CreateAllItemsQuery()) ctx.Load(listItems) ' DOCUMENT CREATION CODE GOES HERE ctx.ExecuteQuery() End Using MessageBox.Show("Document Created!") End If End Sub

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• Safari & Frames in html

  - by user575838

  Hi, I am using Windows Expression web to design a embedded quicktime player that plays 4 separate videos in a main frame. Yes, I am using frames. Header Frame, Left Bar frame, Footer & Main centre frame. Everything works in Explorer as it should. See the picture ![Web Frames preview in Explorer, links work, link plays dif videos when clicked.][1] <html> Untitled 1 <div style="position: absolute; width: 100px; height: 100px; z-index: 1" id="layer1"> </div> <p>This page uses frames, but your browser doesn&#39;t support them.</p> </body> </noframes> When I check it in Safari, the video is misaligned in the frame & the background color is black, which I want it white. All the links work, it's just the misalignment & background color. See the picture. ![Safari Preview][2] Firefox also works. Here's the code, page source from the Safari browser. Heres a pic of Safari misalignment. Heres the Safari Code code Please help. It may be simple but I'm a newb. I appreciate any advice from you pro's.

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• find, excluding dir, not descending into dir, AND using maxdepth and mindepth

  - by user1680819

  This is RHEL 5.6 and GNU find 4.2.27. I am trying to exclude a directory from find, and want to make sure that directory isn't descended into. I've seen plenty of posts saying -prune will do this - and it does. I can run this command: find . -type d -name "./.snapshot*" -prune -o -print and it works. I run it through strace and verify it is NOT descending into .snapshot. I also want to find directories ONLY at a certain level. I can use mindepth and maxdepth to do this: find . -maxdepth 8 -mindepth 8 -type d and it gives me all the dirs 8 levels down, including what's in .snapshot. If I combine the prune and mindepth and maxdepth options: find . -maxdepth 8 -mindepth 8 -type d \( -path "./.snapshot/*" -prune -o -print \) the output is right - I see all the dirs 8 levels down except for what's in .snapshot, but if I run that find through strace, I see that .snapshot is still being descended into - to levels 1 through 8. I've tried a variety of different combinations, moving the precedence parens around, reording expression components - everything that yields the right output still descends into .snapshot. I see in the man page that -prune doesn't work with -depth, but doesn't say anything about mindepth and maxdepth. Can anyone offer any advice? Thanks... Bill

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• matching certain numbers at the end of a string

  - by user697473

  I have a vector of strings: s <- c('abc1', 'abc2', 'abc3', 'abc11', 'abc12', 'abcde1', 'abcde2', 'abcde3', 'abcde11', 'abcde12', 'nonsense') I would like a regular expression to match only the strings that begin with abc and end with 3, 11, or 12. In other words, the regex has to exclude abc1 but not abc11, abc2 but not abc12, and so on. I thought that this would be easy to do with lookahead assertions, but I haven't found a way. Is there one? EDIT: Thanks to posters below for pointing out a serious ambiguity in the original post. In reality, I have many strings. They all end in digits: some in 0, some in 9, some in the digits in between. I am looking for a regex that will match all strings except those that end with a letter followed by a 1 or a 2. (The regex should also match only those strings that start with abc, but that's an easy problem.) I tried to use negative lookahead assertions to create such a regex. But I didn't have any success.

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• Find all A^x in a given range

  - by Austin Henley

  I need to find all monomials in the form AX that when evaluated falls within a range from m to n. It is safe to say that the base A is greater than 1, the power X is greater than 2, and only integers need to be used. For example, in the range 50 to 100, the solutions would be: 2^6 3^4 4^3 My first attempt to solve this was to brute force all combinations of A and X that make "sense." However this becomes too slow when used for very large numbers in a big range since these solutions are used in part of much more intensive processing. Here is the code: def monoSearch(min, max): base = 2 power = 3 while 1: while base**power < max: if base**power > min: print "Found " + repr(base) + "^" + repr(power) + " = " + repr(base**power) power = power + 1 base = base + 1 power = 3 if base**power > max: break I could remove one base**power by saving the value in a temporary variable but I don't think that would make a drastic effect. I also wondered if using logarithms would be better or if there was a closed form expression for this. I am open to any optimizations or alternatives to finding the solutions.

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• capture text, including tags from string, and then reorder tags with text

  - by Brian

  I have the following text: abcdef<CONVERSION>abcabcabcabc<2007-01-12><name1><2007-01-12>abcabcabcabc<name2><2007-01-11>abcabcabcabc<name3><2007-02-12>abcabcabcabc<name4>abcabcabcabc<2007-03-12><name5><date>abcabcabcabc<name6> I need to use regular expressions in order to clean the above text: The basic extraction rule is: <2007-01-12>abcabcabcabc<name2> I have no problem extracting this pattern. My issue is that within th text I have malformed sequences: If the text doesn't start with a date, and end with a name my extraction fails. For example, the text above may have several mal formed sequences, such as: abcabcabcabc<2007-01-12><name1> Should be: <2007-01-12>abcabcabcabc<name1> Is it possible to have a regular expression that would clean the above, prior to extracting my consistent pattern. In short, i need to find all mal formed patterns, and then take the date tag and put it in front of it, as provided in the example above. Thanks.

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• ReplaceAll not working as expected

  - by Tim Kemp

  Still early days with Mathematica so please forgive what is probably a very obvious question. I am trying to generate some parametric plots. I have: ParametricPlot[{ (a + b) Cos[t] - h Cos[(a + b)/b t], (a + b) Sin[t] - h Sin[(a + b)/b t]}, {t, 0, 2 \[Pi]}, PlotRange -> All] /. {a -> 2, b -> 1, h -> 1} No joy: the replacement rules are not applied and a, b and h remain undefined. If I instead do: Hold@ParametricPlot[{ (a + b) Cos[t] - h Cos[(a + b)/b t], (a + b) Sin[t] - h Sin[(a + b)/b t]}, {t, 0, 2 \[Pi]}, PlotRange -> All] /. {a -> 2, b -> 1, h -> 1} it looks like the rules ARE working, as confirmed by the output: Hold[ParametricPlot[{(2 + 1) Cos[t] - 1 Cos[(2 + 1) t], (2 + 1) Sin[t] - 1 Sin[(2 + 1) t]}, {t, 0, 2 \[Pi]}, PlotRange -> All]] Which is what I'd expect. Take the Hold off, though, and the ParametricPlot doesn't work. There's nothing wrong with the equations or the ParametricPlot itself, though, because I tried setting values for a, b and h in a separate expression (a=2; b=1; h=1) and I get my pretty double cardoid out as expected. So, what am I doing wrong with ReplaceAll and why are the transformation rules not working? This is another fundamentally important aspect of MMA that my OOP-ruined brain isn't understanding. I tried reading up on ReplaceAll and ParametricPlot and the closest clue I found was that "ParametricPlot has attribute HoldAll and evaluates f only after assigning specific numerical values to variables" which didn't help much or I wouldn't be here. Thanks.

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• in haskell, why do I need to specify type constraints, why can't the compiler figure them out?

  - by Steve

  Consider the function, add a b = a + b This works: *Main> add 1 2 3 However, if I add a type signature specifying that I want to add things of the same type: add :: a -> a -> a add a b = a + b I get an error: test.hs:3:10: Could not deduce (Num a) from the context () arising from a use of `+' at test.hs:3:10-14 Possible fix: add (Num a) to the context of the type signature for `add' In the expression: a + b In the definition of `add': add a b = a + b So GHC clearly can deduce that I need the Num type constraint, since it just told me: add :: Num a => a -> a -> a add a b = a + b Works. Why does GHC require me to add the type constraint? If I'm doing generic programming, why can't it just work for anything that knows how to use the + operator? In C++ template programming, you can do this easily: #include <string> #include <cstdio> using namespace std; template<typename T> T add(T a, T b) { return a + b; } int main() { printf("%d, %f, %s\n", add(1, 2), add(1.0, 3.4), add(string("foo"), string("bar")).c_str()); return 0; } The compiler figures out the types of the arguments to add and generates a version of the function for that type. There seems to be a fundamental difference in Haskell's approach, can you describe it, and discuss the trade-offs? It seems to me like it would be resolved if GHC simply filled in the type constraint for me, since it obviously decided it was needed. Still, why the type constraint at all? Why not just compile successfully as long as the function is only used in a valid context where the arguments are in Num? Thank you.

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• Problem Binding to a Brush Property in WPF

  - by Krisc

  Working in WPF, writing a custom user control. I am trying to change the background property of the Border element when I change the value of a property of the class. Right now I am working on simply binding it to a DP, though if there is a better way I am open to suggestions. Here is the XAML for the UserControl <UserControl x:Class="MyProject.MyControl" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:js="clr-namespace:MyProject" mc:Ignorable="d" x:Name="MyControlRootLayout" Background="Transparent" d:DesignHeight="300" d:DesignWidth="300" Cursor="Hand"> <Border x:Name="RootBorder" Background="{Binding Path=CoreBackground, ElementName=MyControlRootLayout}" > </Border> </UserControl> And the code... public partial class MyControl : UserControl { public static DependencyProperty IsSelectedProperty = DependencyProperty.Register("IsSelected", typeof(bool), typeof(MyControl)); public static DependencyProperty CoreBackgroundProperty = DependencyProperty.Register("CoreBackground", typeof(Brush), typeof(MyControl)); public MyControl() { CoreBackground = new SolidColorBrush(Color.FromArgb(0, 255, 245, 104)); InitializeComponent(); Margin = new Thickness(5); } public Brush CoreBackground { get { return (Brush)GetValue(CoreBackgroundProperty); } set { SetValue(CoreBackgroundProperty, value); } } public bool IsSelected { get { return (bool)GetValue(IsSelectedProperty); } private set { SetValue(IsSelectedProperty, value); } } } Instead, the background comes out as transparent.

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• C# Linq Select Problem in Method Chain.

  - by Gnought

  Note that the _src inherit IQueryable<U> and V inherit new(); I wrote the following statement, there is no syntax error. IQueryable<V> a = from s in _src where (s.Right - 1 == s.Left) select new V(); But if i re-wrote it as follows, the Visual Studio editor complains an error in the "Select" IQueryable<V> d = _src.Where(s => s.Right - 1 == s.Left).Select(s=> new V()); The Error is: The type arguments cannot be inferred from the usage. Try specifying the type arguments explicitly. Candidates are: System.Collections.Generic.IEnumerable<V> Select<U,V>(this System.Collections.Generic.IEnumerable<U>, System.Func<U,V>) (in class Enumerable) System.Linq.IQueryable<V> Select<U,V>(this System.Linq.IQueryable<U>, System.Linq.Expressions.Expression<System.Func<U,V>>) (in class Queryable) Could anyone explain this phenomenon, and what the solution is to fix the error?

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