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• SQLAlchemy & Complex Queries

  - by user356594

  I have to implement ACL for an existing application. So I added the a user, group and groupmembers table to the database. I defined a ManyToMany relationship between user and group via the association table groupmembers. In order to protect some ressources of the app (i..e item) I added a additional association table auth_items which should be used as an association table for the ManyToMany relationship between groups/users and the specific item. item has following columns: user_id -- user table group_id -- group table item_id -- item table at least on of user_id and group_id columns are set. So it's possible to define access for a group or for a user to a specific item. I have used the AssociationProxy to define the relationship between users/groups and items. I now want to display all items which the user has access to and I have a really hard time doing that. Following criteria are used: All items which are owned by the user should be shown (item.owner_id = user.id) All public items should be shown (item.access = public) All items which the user has access to should be shown (auth_item.user_id = user.id) All items which the group of the user has access to should be shown. The first two criteria are quite straightforward, but I have a hard time doing the 3rd one. Here is my approach: clause = and_(item.access == 'public') if user is not None: clause = or_(clause,item.owner == user,item.users.contains(user),item.groups.contains(group for group in user.groups)) The third criteria produces an error. item.groups.contains(group for group in user.groups) I am actually not sure if this is a good approach at all. What is the best approach when filtering manytomany relationships? How I can filter a manytomany relationship based on another list/relationship? Btw I am using the latest sqlalchemy (6.0) and elixir version Thanks for any insights.

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• Checking if any of a list of values falls within a table of ranges

  - by Conspicuous Compiler

  I'm looking to check whether any of a list of integers fall in a list of ranges. The ranges are defined in a table defined something like: # Extra Type Field Default Null Key 0 int(11) rangeid 0 NO PRI 1 int(11) max 0 NO MUL 2 int(11) min 0 NO MUL Using MySQL 5.1 and Perl 5.10. I can check whether a single value, say 7, is in any of the ranges with a statement like SELECT 1 FROM range WHERE 7 BETWEEN min AND max If 7 is in any of those ranges, I get a single row back. If it isn't, no rows are returned. Now I have a list of, say, 50 of these values, not stored in a table at present. I assemble them using map: my $value_list = '(' . ( join ', ', map { int $_ } @values ) . ')' ; I want to see if any of the items in the list fall inside of any of the ranges, but am not particularly concerned with which number nor which range. I'd like to use a syntax such as: SELECT 1 FROM range WHERE (1, 2, 3, 4, 5, 6, 7, 42, 309, 10000) BETWEEN min AND max MySQL kindly chastises me for such syntax: Operand should contain 1 column(s) I pinged #mysql who were quite helpful. However, having already written this up by the time they responded and thinking it'd be helpful to fix the answer in a more permanent medium, I figured I'd post the question anyhow. Maybe SO will provide a different solution?

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• Best way to use PL/SQL Pacakge Cursors from Pro*C

  - by Greg Reynolds

  I have a cursor defined in PL/SQL, and I am wondering what the best way to use it from Pro*C is. Normally for a cursor defined in Pro*C you would do: EXEC SQL DECLARE curs CURSOR FOR SELECT 1 FROM DUAL; EXEC SQL OPEN curs; EXEC SQL FETCH curs INTO :foo; EXEC SQL CLOSE cusr; I was hoping that the same (or similar) syntax would work for a packaged cursor. For example, I have a package MyPack, with a declaration type MyType is record (X integer); cursor MyCurs(x in integer) return MyType; Now I have in my Pro*C code a rather unsatisfying piece of embedded PL/SQL that opens the cursor, does the fetching etc., as I couldn't get the first style of syntax to work. Using the example EXEC SQL EXECUTE DECLARE XTable is table of MyPack.MyType; BEGIN OPEN MyPack.MyCurs(:param); FETCH MyPack.MyCurs INTO XTable; CLOSE MyPack.MyCurs; END; END-EXEC; Does anyone know if there is a more "Pure" Pro*C approach?

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• Migrate Data and Schema from MySQL to MSSQL

  - by colithium

  Are there any free solutions for automatically migrating a database from MySQL to MSSQL Server that "just works"? I've been attempting this simple (at least I thought so) task all day now. I've tried: MSSQL Server Management Studio's Import Data feature Create an empty database Tasks - Import Data... .NET Framework Data Provider for Odbc Valid DSN (verified it connects) Copy data from one or more tables or views Check 1 VERY simple table Click Preview Get Error: The preview data could not be retrieved. ADDITIONAL INFORMATION: ERROR [42000] [MySQL][ODBC 5.1 Driver][mysqld-5.1.45-community]You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '"table_name"' at line 1 (myodbc5.dll) A similar error occurs if I go through the rest of the wizard and perform the operation. The failed step is "Setting Source Connection" the error refers to retrieving column information and then lists the above error. It can retrieve column information just fine when I modify column mappings so I really don't know what the issue is. I've also tried getting various MySql tools to output ddl statements that MSSQL understand but haven't succeeded. I've tried with MySQL v5.1.11 to SQL Server 2005 and with MySQL v5.1.45 to SQL Server 2008 (with ODBC drivers 3.51.27.00 and 5.01.06.00 respectively)

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• Java Scanner newline parsing with regex (Bug?)

  - by SEK

  I'm developing a syntax analyzer by hand in Java, and I'd like to use regex's to parse the various token types. The problem is that I'd also like to be able to accurately report the current line number, if the input doesn't conform to the syntax. Long story short, I've run into a problem when I try to actually match a newline with the Scanner class. To be specific, when I try to match a newline with a pattern using the Scanner class, it fails. Almost always. But when I perform the same matching using a Matcher and the same source string, it retrieves the newline exactly as you'd expect it too. Is there a reason for this, that I can't seem to discover, or is this a bug, as I suspect? FYI: I was unable to find a bug in the Sun database that describes this issue, so if it is a bug, it hasn't been reported. Example Code: Pattern newLinePattern = Pattern.compile("(\\r\\n?|\\n)", Pattern.MULTILINE); String sourceString = "\r\n\n\r\r\n\n"; Scanner scan = new Scanner(sourceString); scan.useDelimiter(""); int count = 0; while (scan.hasNext(newLinePattern)) { scan.next(newLinePattern); count++; } System.out.println("found "+count+" newlines"); // finds 7 newlines Matcher match = newLinePattern.matcher(sourceString); count = 0; while (match.find()) { count++; } System.out.println("found "+count+" newlines"); // finds 5 newlines

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• How do I interact with a Perl object that has a hash attribute?

  - by brydgesk

  I have a class with several variables, one of which is a hash (_runs): sub new { my ($class, $name) = @_; my $self = { _name => $name, ... _runs => (), _times => [], ... }; bless ($self, $class); return $self; } Now, all I'm trying to do is create an accessor/mutator, as well as another subroutine that pushes new data into the hash. But I'm having a hell of a time getting all the referencing/dereferencing/$self calls working together. I've about burned my eyes out with "Can't use string ("blah") as a HASH ref etc etc" errors. For the accessor, what is 'best practice' for returning hashes? Which one of these options should I be using (if any)?: return $self->{_runs}; return %{ $self->{_runs} }; return \$self->{_runs}; Further, when I'm using the hash within other subroutines in the class, what syntax do I use to copy it? my @runs = $self->{_runs}; my @runs = %{ $self->{_runs} }; my @runs = $%{ $self->{_runs} }; my @runs = $$self->{_runs}; Same goes for iterating over the keys: foreach my $dt (keys $self->{_runs}) foreach my $dt (keys %{ $self->{_runs} }) And how about actually adding the data? $self->{_runs}{$dt} = $duration; %{ $self->{_runs} }{$dt} = $duration; $$self->{_runs}{$dt} = $duration; You get the point. I've been reading articles about using classes, and articles about referencing and dereferencing, but I can't seem to get my brain to combine the knowledge and use both at the same time. I got my _times array working finally, but mimicking my array syntax over to hashes didn't work.

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• Index an array expression directly in PostgreSQL

  - by wich

  I'm trying to insert data into a table from a template table. I need to rewrite one of the columns for which I wanted to use a directly indexed array expression, but I can't seem to find how to do this, if it is even possible. The scenario: create table template ( id integer, index integer, foo integer); insert into template values (0, 1, 23), (0, 2, 18), (0, 3, 16), (0, 4, 7), (1, 1, 17), (1, 2, 26), (1, 3, 11), (1, 4, 3); create table data ( data_id integer, foo integer); Now what I'd like to do is the following: insert into data select (array[3,7,5,2])[index], foo from template where id = 1; But this doesn't work, the (array[3,7,5,2])[index] syntax isn't valid. I tried a few variants, but was unable to get anything working and wasn't able to find the correct syntax in the docs, nor even whether this is at all possible or not. As a current workaround I've devised the following, but it is less than ideal, from an elegance perspective at least, but it may also be a performance hit, I haven't looked into that yet. insert into data select arr[index], foo from template, (select array[3,7,5,2] as arr) as q where id = 1; If anyone could suggest a (better) alternative to accomplish this I'd like to hear that as well.

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• multiple definition in header file

  - by Jérôme

  Here is a small code-example from which I'd like to ask a question : complex.h : #ifndef COMPLEX_H #define COMPLEX_H #include <iostream> class Complex { public: Complex(float Real, float Imaginary); float real() const { return m_Real; }; private: friend std::ostream& operator<<(std::ostream& o, const Complex& Cplx); float m_Real; float m_Imaginary; }; std::ostream& operator<<(std::ostream& o, const Complex& Cplx) { return o << Cplx.m_Real << " i" << Cplx.m_Imaginary; } #endif // COMPLEX_H complex.cpp : #include "complex.h" Complex::Complex(float Real, float Imaginary) { m_Real = Real; m_Imaginary = Imaginary; } main.cpp : #include "complex.h" #include <iostream> int main() { Complex Foo(3.4, 4.5); std::cout << Foo << "\n"; return 0; } When compiling this code, I get the following error : multiple definition of operator<<(std::ostream&, Complex const&) I've found that making this fonction inline solves the problem, but I don't understand why. Why does the compiler complain about multiple definition ? My header file is guarded (with #define COMPLEX_H). And, if complaining about the operator<< fonction, why not complain about the public real() fonction, which is defined in the header as well ? And is there another solution as using the inline keyword ?

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• Creating transparent gridlines

  - by Rob Penridge

  I'm trying to get the chart's gridlines to be transparent but it doesn't seem to be supported: http://support.sas.com/documentation/cdl/en/grstatug/63302/HTML/default/viewer.htm#n1f71f6e9v037an1jy274v66z4r1.htm I'm doing to try and blend the gridlines with the chart background color (which in my code can change between colors) which would make the gridlines subtle rather than jarring when background colors change. Here is my code: ** ** TAKE THE DEFAULT STYLE BEING USED. MODIFY IT SO THAT ** GRAPH GRIDLINES WILL BE GREEN AND MOSTLY TRANSPARENT *; proc template; define style my_style; parent = styles.default; style GraphGridLines from GraphGridLines / contrastcolor=green transparency=.05; end; run; ** ** LAYOUT TEMPLATE FOR A SIMPLE SERIES CHART *; proc template; define statgraph mychart; begingraph; layout overlay / wallcolor=black xaxisopts=(display=(line) griddisplay=on) yaxisopts=(display=(line)) ; seriesplot x=name y=height / lineattrs=(color=white); endlayout; endgraph; end; run; ** ** PLOT SAMPLE DATA USING CUSTOM STYLE AND CHART LAYOUT WE JUST DEFINED *; ods graphics / width=640 height=640 ; ods html style=my_style; proc sgrender data=sashelp.class template=mychart; run; ods html close; Is there another way to achieve this effect by blending the green color with the background color?

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• PostgreSQL: return select count(*) from old_ids;

  - by Alexander Farber

  Hello, please help me with 1 more PL/pgSQL question. I have a PHP-script run as daily cronjob and deleting old records from 1 main table and few further tables referencing its "id" column: create or replace function quincytrack_clean() returns integer as $BODY$ begin create temp table old_ids (id varchar(20)) on commit drop; insert into old_ids select id from quincytrack where age(QDATETIME) > interval '30 days'; delete from hide_id where id in (select id from old_ids); delete from related_mks where id in (select id from old_ids); delete from related_cl where id in (select id from old_ids); delete from related_comment where id in (select id from old_ids); delete from quincytrack where id in (select id from old_ids); return select count(*) from old_ids; end; $BODY$ language plpgsql; And here is how I call it from the PHP script: $sth = $pg->prepare('select quincytrack_clean()'); $sth->execute(); if ($row = $sth->fetch(PDO::FETCH_ASSOC)) printf("removed %u old rows\n", $row['count']); Why do I get the following error? SQLSTATE[42601]: Syntax error: 7 ERROR: syntax error at or near "select" at character 9 QUERY: SELECT select count(*) from old_ids CONTEXT: SQL statement in PL/PgSQL function "quincytrack_clean" near line 23 Thank you! Alex

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• Pull specific information from a long list with Perl

  - by melignus

  The file that I've got to work with here is the result of an LDAP extraction but I need to ultimately get the information formatted over to something that a spreadsheet can use. So, the data is as follows: DataDataDataDataDataDataDataDataDataDataDataDataDataDataDataData DataDataDataDataDataDataDataDataDataDataDataDataDataDataDataData displayName: John Doe name: ##userName DataDataDataDataDataDataDataDataDataDataDataDataDataDataDataData DataDataDataDataDataDataDataDataDataDataDataDataDataDataDataData displayName: Jane Doe name: ##userName DataDataDataDataDataDataDataDataDataDataDataDataDataDataDataData DataDataDataDataDataDataDataDataDataDataDataDataDataDataDataData displayName: Ted Doe name: ##userName The format that I need to export to is: firstName lastName userName firstName lastName userName firstName lastName userName Where the spaces are tabs so I can then impor that file into a database. I have experience doing this in VBScript but I'm trying to switch over to using Perl for as much server administration as possible. I'm not sure on the syntax for what I want which is basically while not endoffile{ detect "displayName: " & $firstName & " " & $lastName detect "name: ##" & $userName write $firstName tab $lastName tab $userName to file } Also if someone could point me to a resource specifically on the text parsing syntax that Perl uses, I'd be very grateful. Most of the resources that I've come across haven't been very helpful.

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• gridview image column problem

  - by jame

  Work on vs05 C# asp.net .My SQL Syntax is :**** if exists (select * from dbo.sysobjects where id = object_id(N'[dbo].[Images]') and OBJECTPROPERTY(id, N'IsUserTable') = 1) drop table [dbo].[Images] GO CREATE TABLE [dbo].[Images] ( [ID] [numeric](18, 0) IDENTITY (1, 1) NOT NULL , [ImageName] [varchar] (50) COLLATE SQL_Latin1_General_CP1_CI_AS NULL , [Image] [image] NULL ) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY] GO I want to show this Images table values in a grid view.....I do it ...but the image value can not show ....asp.net syntax for gridview is <asp:GridView ID="GridView2" runat="server" AutoGenerateColumns="False"> <Columns> <asp:BoundField DataField="ImageName" HeaderText="ImageName" /> <asp:TemplateField HeaderText="Image"> <EditItemTemplate> <asp:TextBox ID="TextBox1" runat="server" Text='<%# Eval("Image") %>'></asp:TextBox> </EditItemTemplate> <ItemTemplate> <asp:Image ID="Image1" runat="server" ImageUrl='<%# Eval("Image") %>' /> </ItemTemplate> </asp:TemplateField> </Columns> </asp:GridView> i write the below code on pageload event. i want images table values must shown when the page is load... string strSQL = "Select * From Images"; DataTable dt = clsDB.getDataTable(strSQL); this.GridView2.DataSource = dt; this.GridView2.DataBind(); Why not i get the image on my image column of the gridview.....what's the problem is how to solve?

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• How do you perform arithmetic calculations on symbols in Scheme/Lisp?

  - by kunjaan

  I need to perform calculations with a symbol. I need to convert the time which is of hh:mm form to the minutes passed. ;; (get-minutes symbol)->number ;; convert the time in hh:mm to minutes ;; (get-minutes 6:19)-> 6* 60 + 19 (define (get-minutes time) (let* ((a-time (string->list (symbol->string time))) (hour (first a-time)) (minutes (third a-time))) (+ (* hour 60) minutes))) This is an incorrect code, I get a character after all that conversion and cannot perform a correct calculation. Do you guys have any suggestions? I cant change the input type. Context: The input is a flight schedule so I cannot alter the data structure. ;; ---------------------------------------------------------------------- Edit: Figured out an ugly solution. Please suggest something better. (define (get-minutes time) (let* ((a-time (symbol->string time)) (hour (string->number (substring a-time 0 1))) (minutes (string->number (substring a-time 2 4)))) (+ (* hour 60) minutes)))

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• MSVC 2003 doesn't see any definitions from a nested include file

  - by ezpresso

  I have a piece of code with COM class declaration as follows: #include "PathTypes.h" MIDL_INTERFACE("552C7555-0555-4444-BA86-56CF39AAFFFF") IPathCalc : public IUnknown { virtual HRESULT STDMETHODCALLTYPE GetLocation( /* [retval][out] */ GeoLocation* pLoc) = 0; virtual HRESULT STDMETHODCALLTYPE SetLocation( /* [in] */ GeoLocation* pLoc) = 0; ... }; Below is the contents of PathTypes.h file: #if !defined(PATHCALC_TYPES_INCLUDED) #define PATHCALC_TYPES_INCLUDED #include "libastro/AstronomyStructs.h" #endif And the libastro/AstronomyStructs.h from an external cross-platform library: #ifndef _ASTRONOMY_STRUCTS_INCLUDED #define _ASTRONOMY_STRUCTS_INCLUDED typedef struct { double lattitude; double longitude; } GeoLocation; ... #endif /* _ASTRONOMY_STRUCTS_INCLUDED */ When I'm trying to build this code with g++ everything goes well. That's not the case with MSVC 2003 which returns error C2061: syntax error : identifier 'GeoLocation'. Seems like MSVC doesn't "see" the definitions from the libastro/AstronomyStructs.h file. When I replace #include "PathTypes.h" with #include "libastro/AstronomyStructs.h" the code compiles without errors. How to make MSVC 2003 to actually "see" the definitions from the nested include files?

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• Alternatives to static methods on interfaces for enforcing consistency

  - by jayshao

  In Java, I'd like to be able to define marker interfaces, that forced implementations to provide static methods. For example, for simple text-serialization/deserialization I'd like to be able to define an interface that looked something like this: public interface TextTransformable<T>{ public static T fromText(String text); public String toText(); Since interfaces in Java can't contain static methods though (as noted in a number of other posts/threads: here, here, and here this code doesn't work. What I'm looking for however is some reasonable paradigm to express the same intent, namely symmetric methods, one of which is static, and enforced by the compiler. Right now the best we can come up with is some kind of static factory object or generic factory, neither of which is really satisfactory. Note: in our case our primary use-case is we have many, many "value-object" types - enums, or other objects that have a limited number of values, typically carry no state beyond their value, and which we parse/de-parse thousands of time a second, so actually do care about reusing instances (like Float, Integer, etc.) and its impact on memory consumption/g.c. Any thoughts?

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• unable to return 'true' value in C function

  - by Byron

  If Im trying to check an input 5 byte array (p) against a 5 byte array stored in flash (data), using the following function (e2CheckPINoverride), to simply return either a true or false value. But it seems, no matter what I try, it only returns as 'false'. I call the function here: if (e2CheckPINoverride(pinEntry) == 1){ PTDD_PTDD1 = 1; } else{ PTDD_PTDD1 = 0; } Here is the function: BYTE e2CheckPINoverride(BYTE *p) { BYTE i; BYTE data[5]; if(e2Read(E2_ENABLECODE, data, 5)) { if(data[0] != p[0]) return FALSE; if(data[1] != p[1]) return FALSE; if(data[2] != p[2]) return FALSE; if(data[3] != p[3]) return FALSE; if(data[4] != p[4]) return FALSE; } return TRUE; } I have already assigned true and false in the defines.h file: #ifndef TRUE #define TRUE ((UCHAR)1) #endif #ifndef FALSE #define FALSE ((UCHAR)0) #endif and where typedef unsigned char UCHAR; when i step through the code, it performs all the checks correctly, it passes in the correct value, compares it correctly and then breaks at the correct point, but is unable to process the return value of true? please help?

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• How to properly implement the Strategy pattern in a web MVC framework?

  - by jboxer

  In my Django app, I have a model (lets call it Foo) with a field called "type". I'd like to use Foo.type to indicate what type the specific instance of Foo is (possible choices are "Number", "Date", "Single Line of Text", "Multiple Lines of Text", and a few others). There are two things I'd like the "type" field to end up affecting; the way a value is converted from its normal type to text (for example, in "Date", it may be str(the_date.isoformat())), and the way a value is converted from text to the specified type (in "Date", it may be datetime.date.fromtimestamp(the_text)). To me, this seems like the Strategy pattern (I may be completely wrong, and feel free to correct me if I am). My question is, what's the proper way to code this in a web MVC framework? In a client-side app, I'd create a Type class with abstract methods "serialize()" and "unserialize()", override those methods in subclasses of Type (such as NumberType and DateType), and dynamically set the "type" field of a newly-instantiated Foo to the appropriate Type subclass at runtime. In a web framework, it's not quite as straightforward for me. Right now, the way that makes the most sense is to define Foo.type as a Small Integer field and define a limited set of choices (0 = "Number", 1 = "Date", 2 = "Single Line of Text", etc.) in the code. Then, when a Foo object is instantiated, use a Factory method to look at the value of the instance's "type" field and plug in the correct Type subclass (as described in the paragraph above). Foo would also have serialize() and unserialize() methods, which would delegate directly to the plugged-in Type subclass. How does this design sound? I've never run into this issue before, so I'd really like to know if other people have, and how they've solved it.

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• How can I modified the value of a string defined in a struc?

  - by Eric

  Hi, I have the following code in c++: define TAM 4000 define NUMPAGS 512 struct pagina { bitset<12 direccion; char operacion; char permiso; string *dato; int numero; }; void crearPagina(pagina* pag[], int pos, int dir) { pagina * paginas = (pagina*)malloc(sizeof(char) * TAM); paginas - direccion = bitset<12 (dir); paginas - operacion = 'n'; paginas - permiso = 'n'; string **tempDato = &paginas - dato; char *temp = " "; **tempDato = temp; paginas - numero = 0; pag[pos] = paginas; } I want to modify the value of the variable called "string *dato" in the struct pagina but, everytime I want to assing a new value, the compiler throws a segmentation fault. In this case I'm using a pointer to string, but I have also tried with a string. In a few words I want to do the following: pagina - dato = "test"; Any idea? Thanks in advance!!!

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• How best to deal with warning c4305 when type could change?

  - by identitycrisisuk

  I'm using both Ogre and NxOgre, which both have a Real typedef that is either float or double depending on a compiler flag. This has resulted in most of our compiler warnings now being: warning C4305: 'argument' : truncation from 'double' to 'Ogre::Real' When initialising variables with 0.1 for example. Normally I would use 0.1f but then if you change the compiler flag to double precision then you would get the reverse warning. I guess it's probably best to pick one and stick with it but I'd like to write these in a way that would work for either configuration if possible. One fix would be to use #pragma warning (disable : 4305) in files where it occurs, I don't know if there are any other more complex problems that can be hidden by not having this warning. I understand I would push and pop these in header files too so that they don't end up spreading across code. Another is to create some macro based on the accuracy compiler flag like: #if OGRE_DOUBLE_PRECISION #define INIT_REAL(x) (x) #else #define INIT_REAL(x) static_cast<float>( x ) #endif which would require changing all the variable initialisation done so far but at least it would be future proof. Any preferences or something I haven't thought of?

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• JavaScript Module Pattern - What about using "return this"?

  - by Rob

  After doing some reading about the Module Pattern, I've seen a few ways of returning the properties which you want to be public. One of the most common ways is to declare your public properties and methods right inside of the "return" statement, apart from your private properties and methods. A similar way (the "Revealing" pattern) is to provide simply references to the properties and methods which you want to be public. Lastly, a third technique I saw was to create a new object inside your module function, to which you assign your new properties before returning said object. This was an interesting idea, but requires the creation of a new object. So I was thinking, why not just use "this.propertyName" to assign your public properties and methods, and finally use "return this" at the end? This way seems much simpler to me, as you can create private properties and methods with the usual "var" or "function" syntax, or use the "this.propertyName" syntax to declare your public methods. Here's the method I'm suggesting: (function() { var privateMethod = function () { alert('This is a private method.'); } this.publicMethod = function () { alert('This is a public method.'); } return this; })(); Are there any pros/cons to using the method above? What about the others?

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• Why there is no scoped locks for multiple mutexes in C++0x or Boost.Thread?

  - by Vicente Botet Escriba

  C++0x thread library or Boost.thread define non-member variadic template function that lock all lock avoiding dead lock. template <class L1, class L2, class... L3> void lock(L1&, L2&, L3&...); While this function avoid help to deadlock, the standard do not includes the associated scoped lock to write exception safe code. { std::lock(l1,l2); // do some thing // unlock li l2 exception safe } That means that we need to use other mechanism as try-catch block to make exception safe code or define our own scoped lock on multiple mutexes ourselves or even do that { std::lock(l1,l2); std::unique_lock lk1(l1, std::adopted); std::unique_lock lk2(l2, std::adopted); // do some thing // unlock li l2 on destruction of lk1 lk2 } Why the standard doesn't includes a scoped lock on multiple mutexes of the same type, as for example { std::array_unique_lock<std::mutex> lk(l1,l2); // do some thing // unlock l1 l2 on destruction of lk } or tuples of mutexes { std::tuple_unique_lock<std::mutex, std::recursive_mutex> lk(l1,l2); // do some thing // unlock l1 l2 on destruction of lk } Is there something wrong on the design?

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• Perl - Using hashes in classes

  - by brydgesk

  I have a class with several variables, one of which is a hash (_runs): sub new { my ($class, $name) = @_; my $self = { _name => $name, ... _runs => (), _times => [], ... }; bless ($self, $class); return $self; } Now, all I'm trying to do is create an accessor/mutator, as well as another subroutine that pushes new data into the hash. But I'm having a hell of a time getting all the referencing/dereferencing/$self calls working together. I've about burned my eyes out with "Can't use string ("blah") as a HASH ref etc etc" errors. For the accessor, what is 'best practice' for returning hashes? Which one of these options should I be using (if any)?: return $self->{_runs}; return %{ $self->{_runs} }; return \$self->{_runs}; Further, when I'm using the hash within other subroutines in the class, what syntax do I use to copy it? my @runs = $self->{_runs}; my @runs = %{ $self->{_runs} }; my @runs = $%{ $self->{_runs} }; my @runs = $$self->{_runs}; Same goes for iterating over the keys: foreach my $dt (keys $self->{_runs}) foreach my $dt (keys %{ $self->{_runs} }) And how about actually adding the data? $self->{_runs}{$dt} = $duration; %{ $self->{_runs} }{$dt} = $duration; $$self->{_runs}{$dt} = $duration; You get the point. I've been reading articles about using classes, and articles about referencing and dereferencing, but I can't seem to get my brain to combine the knowledge and use both at the same time. I got my _times array working finally, but mimicking my array syntax over to hashes didn't work.

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• how to use two count or more on one selecting statament ..?

  - by jjj

  i develop this code: SELECT COUNT(NewEmployee.EmployeeID), NewEmployee.EmployeeId,EmployeeName FROM NewEmployee INNER JOIN NewTimeAttendance ON NewEmployee.EmployeeID = NewTimeAttendance.EmployeeID and NewTimeAttendance.TotalTime is null and (NewTimeAttendance.note = '' or NewTimeAttendance.note is null ) and (month=1 or month =2 or month = 3) GROUP BY NewEmployee.EmployeeID, EmployeeName order by EmployeeID from my previous two question selecting null stuff and counting issue...that amazing code is working beautifully fine..but now i need to select more than one count... ...searched (google) .... found alias...tried: SELECT COUNT(NewEmployee.EmployeeID) as attenddays, COUNT(NewEmployee.EmployeeID) as empabsent , NewEmployee.EmployeeId,EmployeeName FROM NewEmployee INNER JOIN NewTimeAttendance ON empabsent =NewEmployee.EmployeeID = NewTimeAttendance.EmployeeID and NewTimeAttendance.TotalTime is null and (NewTimeAttendance.note = '' or NewTimeAttendance.note is null ) and (month=1 or month =2 or month = 3) , attenddays = NewTimeAttendance.EmployeeID and NewTimeAttendance.TotalTime is null and (NewTimeAttendance.note = '' or NewTimeAttendance.note is null ) and (month=1 or month =2 or month = 3) GROUP BY NewEmployee.EmployeeID, EmployeeName order by EmployeeID Incorrect syntax near '='. second try: SELECT COUNT(NewEmployee.EmployeeID) as attenddays, COUNT(NewEmployee.EmployeeID) as absentdays, NewEmployee.EmployeeId,EmployeeName FROM NewEmployee INNER JOIN NewTimeAttendance ON attenddays(NewEmployee.EmployeeID = NewTimeAttendance.EmployeeID and NewTimeAttendance.TotalTime is null and (NewTimeAttendance.note = '' or NewTimeAttendance.note is null ) and (month=1 or month =2 or month = 3)) , absentdays(NewEmployee.EmployeeID = NewTimeAttendance.EmployeeID and NewTimeAttendance.TotalTime is null and (NewTimeAttendance.note = '' or NewTimeAttendance.note is null ) and (month=1 or month =2 or month = 3)) GROUP BY NewEmployee.EmployeeID, EmployeeName order by EmployeeID Incorrect syntax near '='. not very good ideas... so ...help thanks in advance

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• SQL query error while trying to put a file in the database

  - by DaGhostman Dimitrov

  Hey Guys I have a big problem that I have no Idea why.. I have few forms that upload files to the database, all of them work fine except one.. I use the same query in all(simple insert). I think that it has something to do with the files i am trying to upload but I am not sure. Here is the code: if ($_POST['action'] == 'hndlDocs') { $ref = $_POST['reference']; // Numeric value of $doc = file_get_contents($_FILES['doc']['tmp_name']); $link = mysqli_connect('localhost','XXXXX','XXXXX','documents'); mysqli_query($link,"SET autocommit = 0"); $query = "INSERT INTO documents ({$ref}, '{$doc}', '{$_FILES['doc']['type']}') ;"; mysqli_query($link,$query); if (mysqli_error($link)) { var_dump(mysqli_error($link)); mysqli_rollback($link); } else { print("<script> window.history.back(); </script>"); mysqli_commit($link); } } The database has only these fields: DATABASE documents ( reference INT(5) NOT NULL, //it is unsigned zerofill doc LONGBLOB NOT NULL, //this should contain the binary data mime_type TEXT NOT NULL // the mime type of the file php allows only application/pdf and image/jpeg ); And the error I get is : You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '00001, '????' at line 1 I will appreciate every help. Cheers!

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• reading newlines with FORMAT statement

  - by peter.murray.rust

  I'm writing a preprocessor and postprocessor for Fortran input and output using FORMAT-like statements (there are reasons not to use a FORTRAN library). I want to treat the new line ("/") character correctly. I don't have a Fortran compiler immediately to hand. Is there a simple algorithm for working out how many newlines are written or consumed (This post just gives reading examples) [Please assume a FORTRAN77-like mentality in the FORTRAN code and correct any FORTRAN syntax on my part] UPDATE: no comments yet so I am reduced to finding a compiler and running it myself. I'll post the answers if I'm not beaten to it. No-one commented I had the format syntax wrong. I've changed it but there may still be errors Assume datafile 1 a b c d etc... (a) does the READ command always consume a newline? does READ(1, '(A)') A READ(1, '(A)') B give A='a' and B='b' (b) what does READ(1,'(A,/)') A READ(1,'(A)') B give for B? (I would assume 'c') (c) what does READ(1, '(/)') READ(1, '(A)') A give for A (is it 'b' or 'c') (d) what does READ(1,'(A,/,A)') A, B READ(1,'(A)') C give for A and B and C(can I assume 'a' and 'b' and 'c') (e) what does READ(1,'(A,/,/,A)') A, B READ(1,'(A)') C give for A and B and C(can I assume 'a' and 'c' and 'd')? Are there any cases in which the '/' is redundant?

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