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• Imports and Depends

  - by David Diez

  I have read two recent posts that discuss Depends and Imports but I have four lingering, related questions: Suppose I want two packages to also be available to the end-user when they load in my package. Is there a good reason not to use Depends in this context? (The point here is to load all three packages via a command that loads just the one package.) Is it okay to specify a package in both the Depends and Imports fields? If a package is listed in Depends, is there a point to also listing it in Imports? Or are the benefits of Imports already negated by using Depends? [Added Question] Is the following correct? A package should be listed in the Imports field of the DESCRIPTION file if and only if the package is imported (in whole or in part) in the NAMESPACE file. Thanks much! David

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• ECS with Go - circular imports [migrated]

  - by Andreas

  I'm exploring both Go and Entity-Component-Systems. I understand how ECS works, and I'm trying to replicate what seems to be the go-to document of ECS, namely http://cowboyprogramming.com/2007/01/05/evolve-your-heirachy/ For performance, the document recommends to use static arrays of every component type. That is, not arrays of component interfaces (arrays of pointers). The problem with this in Go is circular imports. I have one package, ecs, which contains the definitions for Entity, Component and System types/interfaces as well as an EntityManager. Another package, ecs/components, contains the various components. Obviously, the ecs/components package depends on ecs. But, to declare arrays of specific components in EntityManager, ecs would depend on ecs/components, therefore creating a circular import. Is there any way of avoiding this? I am aware that normally a high level system should not depend on lower systems. I'm also want to point out that using an array of pointers is probably fast enough for my purposes, but I'm interested in possible workarounds (for future reference) Thank you for your help!

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• What is the scope of xsl apply-imports?

  - by calavera.info

  My original idea about apply-imports was that if there are two templates which matches the same node, then using apply-imports in a template with higher priority runs the template with the lower priority. But I recently find out that it's important how are imports organized. Two cases interests me particularly. Will apply imports work on a template which is imported in imported file (nested import)? How about a "sibling import" (master file imports two files with templates matching the same nodes) It seems to me that this is not clearly described in specification. Could someone provide authoritative guidelines? EDIT: I can try those cases on my own, but there is always a danger that it will be implementation specific behavior.

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• What's wrong with relative imports in Python?

  - by Oddthinking

  I recently upgraded versions of pylint, a popular Python style-checker. It has gone ballistic throughout my code, pointing out places where I import modules in the same package, without specifying the full package path. The new error message is W0403. W0403: Relative import %r, should be %r Used when an import relative to the package directory is detected. Example For example, if my packages are structured like this: /cake /__init__.py /icing.py /sponge.py /drink and in the sponge package I write: import icing instead of import cake.icing I will get this error. While I understand that not all Pylint messages are of equal importance, and I am not afraid to dismiss them, I don't understand why such a practice is considered a poor idea. I was hoping someone could explain the pitfalls, so I could improve my coding style rather than (as I currently plan to do) turning off this apparently spurious warning.

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• Pig_Cassandra integration caused - ERROR 1070: Could not resolve CassandraStorage using imports:

  - by Le Dude

  I'm following basic Pig, Cassandra, Hadoop installation. Everything works just fine as a stand alone. No error. However when I tried to run the example file provided by Pig_cassandra example, I got this error. [root@localhost pig]# /opt/cassandra/apache-cassandra-1.1.6/examples/pig/bin/pig_cassandra -x local -x local /opt/cassandra/apache-cassandra-1.1.6/examples/pig/example-script.pig Using /opt/pig/pig-0.10.0/pig-0.10.0-withouthadoop.jar. 2012-10-24 21:14:58,551 [main] INFO org.apache.pig.Main - Apache Pig version 0.10.0 (r1328203) compiled Apr 19 2012, 22:54:12 2012-10-24 21:14:58,552 [main] INFO org.apache.pig.Main - Logging error messages to: /opt/pig/pig_1351138498539.log 2012-10-24 21:14:59,004 [main] INFO org.apache.pig.backend.hadoop.executionengine.HExecutionEngine - Connecting to hadoop file system at: file:/// 2012-10-24 21:14:59,472 [main] ERROR org.apache.pig.tools.grunt.Grunt - ERROR 1070: Could not resolve CassandraStorage using imports: [, org.apache.pig.builtin., org.apache.pig.impl.builtin.] Details at logfile: /opt/pig/pig_1351138498539.log Here is the log file Pig Stack Trace --------------- ERROR 1070: Could not resolve CassandraStorage using imports: [, org.apache.pig.builtin., org.apache.pig.impl.builtin.] org.apache.pig.impl.logicalLayer.FrontendException: ERROR 1000: Error during parsing. Could not resolve CassandraStorage using imports: [, org.apache.pig.builtin., org.apache.pig.impl.builtin.] at org.apache.pig.PigServer$Graph.parseQuery(PigServer.java:1597) at org.apache.pig.PigServer$Graph.registerQuery(PigServer.java:1540) at org.apache.pig.PigServer.registerQuery(PigServer.java:540) at org.apache.pig.tools.grunt.GruntParser.processPig(GruntParser.java:970) at org.apache.pig.tools.pigscript.parser.PigScriptParser.parse(PigScriptParser.java:386) at org.apache.pig.tools.grunt.GruntParser.parseStopOnError(GruntParser.java:189) at org.apache.pig.tools.grunt.GruntParser.parseStopOnError(GruntParser.java:165) at org.apache.pig.tools.grunt.Grunt.exec(Grunt.java:84) at org.apache.pig.Main.run(Main.java:555) at org.apache.pig.Main.main(Main.java:111) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:601) at org.apache.hadoop.util.RunJar.main(RunJar.java:156) Caused by: Failed to parse: Cannot instantiate: CassandraStorage at org.apache.pig.parser.QueryParserDriver.parse(QueryParserDriver.java:184) at org.apache.pig.PigServer$Graph.parseQuery(PigServer.java:1589) ... 14 more Caused by: java.lang.RuntimeException: Cannot instantiate: CassandraStorage at org.apache.pig.impl.PigContext.instantiateFuncFromSpec(PigContext.java:510) at org.apache.pig.parser.LogicalPlanBuilder.validateFuncSpec(LogicalPlanBuilder.java:791) at org.apache.pig.parser.LogicalPlanBuilder.buildFuncSpec(LogicalPlanBuilder.java:780) at org.apache.pig.parser.LogicalPlanGenerator.func_clause(LogicalPlanGenerator.java:4583) at org.apache.pig.parser.LogicalPlanGenerator.load_clause(LogicalPlanGenerator.java:3115) at org.apache.pig.parser.LogicalPlanGenerator.op_clause(LogicalPlanGenerator.java:1291) at org.apache.pig.parser.LogicalPlanGenerator.general_statement(LogicalPlanGenerator.java:789) at org.apache.pig.parser.LogicalPlanGenerator.statement(LogicalPlanGenerator.java:507) at org.apache.pig.parser.LogicalPlanGenerator.query(LogicalPlanGenerator.java:382) at org.apache.pig.parser.QueryParserDriver.parse(QueryParserDriver.java:175) ... 15 more Caused by: org.apache.pig.backend.executionengine.ExecException: ERROR 1070: Could not resolve CassandraStorage using imports: [, org.apache.pig.builtin., org.apache.pig.impl.builtin.] at org.apache.pig.impl.PigContext.resolveClassName(PigContext.java:495) at org.apache.pig.impl.PigContext.instantiateFuncFromSpec(PigContext.java:507) ... 24 more ================================================================================ I googled around and got to this point from other stackoverflow user that identified the potential problem but not the solution. Cassandra and pig integration cause error during startup I believe my configuration is correct and the path has already been defined properly. I didn't change anything in the pig_cassandra file. I'm not quite sure how to proceed from here. Please help?

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• warning BC40056: Namespace or type specified in the Imports 'MS.Internal.Xaml.Builtins' doesn't cont

  - by Heinzi

  I have a WPF VB.NET project in Visual Studio 2008. For some reason, Visual Studio thinks that it needs to add an Imports MS.Internal.Xaml.Builtins to every auto-generated XAML partial class (= the nameOfXamlFile.g.vb files), resulting in the following warning: warning BC40056: Namespace or type specified in the Imports 'MS.Internal.Xaml.Builtins' doesn't contain any public member or cannot be found. Make sure the namespace or the type is defined and contains at least one public member. Make sure the imported element name doesn't use any aliases. I can remove the Imports line, but, since this is an auto-generated file, it reappears every time that the project is rebuilt. This warning message is annoying and clutters my error list. Is ther something that can be done about it? Or is it a known bug?

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• Import added does not appear in the Imports collection (Msbuild Project)

  - by sebastian

  The title pretty much says it all... this code does not write anything to the console cause the collection is empty. Project p = new Project(engine); p.AddNewImport(@"C:\mytarget.targets",""); foreach(Import imp in p.Imports) Console.WriteLine(p.ProjectPath); But!, if I debug the code the collections get the imports, I guess it has to do with timming? :(

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• Include all imports in Air application Bundle?

  - by Carlos Barbosa

  How can I import all files and classes into my AIR bundle... it must take a note that I created first a flex project, and set it's main class as Actionscript (.as) . When I build a release all my imports (org) etc.. are not included in the .AIR installer... i have checked this by installing the app and then after show package contents, notice that the diretory structure exists but it doesn't include any of other .as used as imports... import org.papervision3d.cameras.Camera3D; import org.papervision3d.materials.BitmapFileMaterial; import org.papervision3d.materials.utils.MaterialsList; import org.papervision3d.objects.DisplayObject3D;

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• How does QuickBooks handle IIF imports?

  - by dwwilson66

  I've received a 'template' for an IIF file for Quickbooks transactions, and there's like seventy-bazillion fields in there, lots of which I never even user. It's a tab delimited file, with the following lines--field headers for transactions and respective splits for those transactions, followed by an end-of-transaction marker. !TRNS FIELD1 FIELD2 FIELD3 ... FIELD48 !SPL FIELD1 FIELD2 FIELD3 ... FIELD48 !ENDTRNS TRNS FIELD1_DATA FIELD2_DATA FIELD3_DATA ... FIELD48_DATA SPL FIELD1_DATA FIELD2_DATA FIELD3_DATA ... FIELD48_DATA ENDTRNS ... What drives data to a particular field? Is it the field header with corresponding data, or is it the tabular position relative to the head of the line? E.G., Let's say all I have to import is the data in FIELD1, FIELD3 and FIELD5: Would I need by header: !TRNS FIELD1 FIELD3 FIELD5 !SPL FIELD1 FIELD3 FIELD5 !ENDTRNS TRNS FIELD1 FIELD3 FIELD5 SPL FIELD1 FIELD3 FIELD5 ENDTRNS or by tabular position: !TRNS FIELD1 FIELD2 FIELD3 FIELD4 FIELD5 !SPL FIELD1 FIELD2 FIELD3 FIELD4 FIELD5 !ENDTRNS TRNS FIELD1_DATA FIELD2_BLANK FIELD3_DATA FIELD4_BLANK FIELD5_DATA SPL FIELD1_DATA FIELD2_BLANK FIELD3_DATA FIELD4_BLANK FIELD5_DATA ENDTRNS Alternately, if it were a comma delimited input, would I need: DATA1,DATA3,DATA5 or DATA1,,DATA3,,DATA5 Anyone have any experience with what Quickbooks is doing?

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• Python: circular imports needed for type checking

  - by phild

  First of all: I do know that there are already many questions and answers to the topic of the circular imports. The answer is more or less: "Design your Module/Class structure properly and you will not need circular imports". That is true. I tried very hard to make a proper design for my current project, I in my opinion I was successful with this. But my specific problem is the following: I need a type check in a module that is already imported by the module containing the class to check against. But this throws an import error. Like so: foo.py: from bar import Bar class Foo(object): def __init__(self): self.__bar = Bar(self) bar.py: from foo import Foo class Bar(object): def __init__(self, arg_instance_of_foo): if not isinstance(arg_instance_of_foo, Foo): raise TypeError() Solution 1: If I modified it to check the type by a string comparison, it will work. But I dont really like this solution (string comparsion is rather expensive for a simple type check, and could get a problem when it comes to refactoring). bar_modified.py: from foo import Foo class Bar(object): def __init__(self, arg_instance_of_foo): if not arg_instance_of_foo.__class__.__name__ == "Foo": raise TypeError() Solution 2: I could also pack the two classes into one module. But my project has lots of different classes like the "Bar" example, and I want to seperate them into different module files. After my own 2 solutions are no option for me: Has anyone a nicer solution for this problem?

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• How to add imports to groovysh on startup?

  - by ipolevoy

  I'm working on a project where I'd like users to experiment with Java classes on Groovysh. I'd like to make it convenient for them and want to import certain packages by default, when groovysh starts up so that users would not have to re-type the same imports every time they start the shell. Does anyone know how to accomplish this? Thanks in advance, igor

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• A way to automatically organize #imports in Xcode

  - by Arrel

  I love the "Organize Imports" command in Eclipse to implicitly add and remove classes imported into a source file (as in Java or ActionScript). Is there a command in Xcode to update the #import directives at the top of.m Objective-C files based on the classes referenced within the file?

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• Order of imports in C#

  - by BrianK

  How do you like to arrange your "using xxx" imports in C#? I got bored the other day and put them in order from shortest to longest. using System; using System.Web; using System.Data; using System.Linq; using System.Web.UI; using Telerik.Web.UI; using System.Drawing; using System.Collections; using System.Configuration; using System.Web.UI.WebControls; using System.Collections.Generic; Brian

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• detecting circular imports

  - by wallacoloo

  I'm working with a project that contains about 30 unique modules. It wasn't designed too well, so it's common that I create circular imports when adding some new functionality to the project. Of course, when I add the circular import, I'm unaware of it. Sometimes it's pretty obvious I've made a circular import when I get an error like AttributeError: 'module' object has no attribute 'attribute' where I clearly defined 'attribute'. But other times, the code doesn't throw exceptions because of the way it's used. So, to my question: Is it possible to programmatically detect when and where a circular import is occuring?

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• Python preprocessing imports

  - by FiloSottile

  I am managing a quite large python code base (2000 lines) that I want anyway to be available as a single runnable python script. So I am searching for a method or a tool to merge a development folder, made of different python files into a single running script. The thing/method I am searching for should take code split into different files, maybe with a starting __init___.py file that contains the imports and merge it into a single, big script. Much like a preprocessor. Best if a near-native way, better if I can anyway run from the dev folder. I have already checked out pypp and pypreprocessor but they don't seem to take the point. Something like a strange use of __import__() or maybe a bunch of from foo import * replaced by the preprocessor with the code? Obviously I only want to merge my directory and not common libraries.

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• python __import__() imports from 2 different directories when same module exists in 2 locations

  - by programer_gramer

  Hi, I have a python application , which has directory structure like this. -pythonapp -mainpython.py -module1 -submodule1 -file1.py -file2.py -submodule2 -file3.py -file3.py -submodule3 -file1.py -file2.py -file5.py -file6.py -file7.py when I try to import the python utilities(from mainpython.py) under submodule3 , I get the initial 2 files from submodule1.(please note that submodule1 and 3 have 2 different files with the same name). However the same import works fine when there is no conflict i.e it correctly imports file 5,6,7 from submodule3. Here is the code : name=os.path.splitext(os.path.split("module1\submodule3\file1.py")[1])[0] -- file1.py name here is passed dynamically. module = import(name) //Here is name is like "file1" it works(but with the above said issue, though, when passes the name of the file dynamically), but if I pass complete package as "module1.submodule1.file1" it fails with an ImportError saying that "no module with name file1" Now the question is how do we tell the interpreter to use only the ones under "module1.submodule3.file2"? I am using python This is really urgent one and I have run out of all the tries. Hope some experienced python developers can solve this for me?

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• How do display a UserControl with satisfying all imports

  - by Yost

  Dear SO, I'm having some issues with Silverlight 4/ MEF. I have a basic framework setup with a Silverlight Navigation app at the core. Image link to the diagram for clarification The main app (Desu) contains some pages and controls that export en import nicely. I dynamicly load controls from Desu.Controls(like an imageviewer which i identify with the IImageViewer interface) and some pages from Desu.Pages. The first problem I had was with dynamicly loading pages and being able to navigate to these pages (eg. use dummyhttp://blagh/desutestpage.aspx#/Activation when Desu.Pages was loaded from the xap). I solved this by using a custom MetaAttribute and a custom contentloader. Now for the question part: I want to load the ImageViewerControl from Desu.Controls in HomePage in Desu. I haven't loaded the Desu.Controls into the package though. When i try to load the control it gives me CompositionException because it can't satisfy the ImageViewControl import. I tried setting AllowRecomposition=true but that didn't help. So is it possible to load a control without satisfying all imports and, if yes, how does one do this?

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• Having trouble getting MEF imports to be resolved

  - by Dave

  This is sort of a continuation of one of my earlier posts, which involves the resolving of modules in my WPF application. This question is specifically related to the effect of interdependencies of modules and the method of constructing those modules (i.e. via MEF or through new) on MEF's ability to resolve relationships. First of all, here is a simple UML diagram of my test application: I have tried two approaches: left approach: the App implements IError right approach: the App has a member that implements IError Left approach My code behind looked like this (just the MEF-related stuff): // app.cs [Export(typeof(IError))] public partial class Window1 : Window, IError { [Import] public CandyCo.Shared.LibraryInterfaces.IPlugin Plugin { get; set; } [Export] public CandyCo.Shared.LibraryInterfaces.ICandySettings Settings { get; set; } private ICandySettings Settings; public Window1() { // I create the preferences here with new, instead of using MEF. I wonder // if that's my whole problem? If I use MEF, and want to have parameters // going to the constructor, then do I have to [Export] a POCO (i.e. string)? Settings = new CandySettings( "Settings", @"c:\settings.xml"); var catalog = new DirectoryCatalog( "."); var container = new CompositionContainer( catalog); try { container.ComposeParts( this); } catch( CompositionException ex) { foreach( CompositionError e in ex.Errors) { string description = e.Description; string details = e.Exception.Message; } throw; } } } // plugin.cs [Export(typeof(IPlugin))] public class Plugin : IPlugin { [Import] public CandyCo.Shared.LibraryInterfaces.ICandySettings CandySettings { get; set; } [Import] public CandyCo.Shared.LibraryInterfaces.IError ErrorInterface { get; set; } [ImportingConstructor] public Plugin( ICandySettings candy_settings, IError error_interface) { CandySettings = candy_settings; ErrorInterface = error_interface; } } // candysettings.cs [Export(typeof(ICandySettings))] public class CandySettings : ICandySettings { ... } Right-side approach Basically the same as the left-side approach, except that I created a class that inherits from IError in the same assembly as Window1. I then used an [Import] to try to get MEF to resolve that for me. Can anyone explain how the two ways I have approached MEF here are flawed? I have been in the dark for so long that instead of reading about MEF and trying different suggestions, I've added MEF to my solution and am stepping into the code. The part where it looks like it fails is when it calls partManager.GetSavedImport(). For some reason, the importCache is null, which I don't understand. All the way up to this point, it's been looking at the part (Window1) and trying to resolve two imported interfaces -- IError and IPlugin. I would have expected it to enter code that looks at other assemblies in the same executable folder, and then check it for exports so that it knows how to resolve the imports...

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• Finding contained bordered regions from Excel imports.

  - by dmaruca

  I am importing massive amounts of data from Excel that have various table layouts. I have good enough table detection routines and merge cell handling, but I am running into a problem when it comes to dealing with borders. Namely performance. The bordered regions in some of these files have meaning. Data Setup: I am importing directly from Office Open XML using VB6 and MSXML. The data is parsed from the XML into a dictionary of cell data. This wonks wonderfully and is just as fast as using docmd.transferspreadsheet in Access, but returns much better results. Each cell contains a pointer to a style element which contains a pointer to a border element that defines the visibility and weight of each border (this is how the data is structured inside OpenXML, also). Challenge: What I'm trying to do is find every region that is enclosed inside borders, and create a list of cells that are inside that region. What I have done: I initially created a BFS(breadth first search) fill routine to find these areas. This works wonderfully and fast for "normal" sized spreadsheets, but gets way too slow for imports into the thousands of rows. One problem is that a border in Excel could be stored in the cell you are checking or the opposing border in the adjacent cell. That's ok, I can consolidate that data on import to reduce the number of checks needed. One thing I thought about doing is to create a separate graph that outlines the cells using the borders as my edges and using a graph algorithm to find regions that way, but I'm having trouble figuring out how to implement the algorithm. I've used Dijkstra in the past and thought I could do similar with this. So I can span out using no endpoint to search the entire graph, and if I encounter a closed node I know that I just found an enclosed region, but how can I know if the route I've found is the optimal one? I guess I could flag that to run a separate check for the found closed node to the previous node ignoring that one edge. This could work, but wouldn't be much better performance wise on dense graphs. Can anyone else suggest a better method? Thanks for taking the time to read this.

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• Eclipse CSS plugin support css imports

  - by Alex Ivasyuv

  Hi, Is there any CSS plugin for Eclipse, which supports import CSS files to profile, e.g. like Spket IDE makes it for JavaScript files. In result, I want to get the following functionality: In any html/css file, where defined css class/id, I perform clicking on it, and it dispatches me to appropriate css file which responsables for that style, or shows me in left side panel it styles. Does anyone know such plugin for CSS Eclipse? Thanks,

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• Can XMLCatalog be used for schema imports?

  - by jon077

  Can you use XMLCatalog to resolve xsds in schema import statements? If so, what is the preferred/best practice? I want to package the xsds in a jar, so using a relative schemaLocation has not worked. So far I am trying to do something like: SchemaFactory factory = SchemaFactory .newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI); XMLCatalogResolver catalogResolver = new XMLCatalogResolver( new String[]{"/path/to/catalog.xml"}); factory.setResourceResolver(catalogResolver); Schema schema = factory.newSchema(new StreamSource(ClassLoader .getSystemResourceAsStream("config.xsd"))); Without much luck.

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• Building Java projects with circular imports in Eclipse

  - by Buggieboy

  I have a legacy Java (not my native language) app that I'm trying to build in Eclipse Galileo. As it's not my own, I can't speak to the quality of the design, but I am coming across a number of instances where I'll have something like this: In a project called, say, "lib_a", I'll have a file containing this: import com.acme.lib_b.onething; Project "lib_b" on the other hand, will contain: import com.acme.lib_a.anotherthing; Of course, the problem is that one project can't be built because the errors prevent me from creating a .jar file that can be added as an external archive to the other project, and vice versa. It seems to me that this must be a fairly common occurence in building Java applications. Rewriting it from scratch is not an option here, so I'd like to know "what other folks do."

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• How to do relative imports in Python?

  - by Joril

  Imagine this directory structure: app/ __init__.py sub1/ __init__.py mod1.py sub2/ __init__.py mod2.py I'm coding mod1, and I need to import something from mod2. How should I do it? I tried from ..sub2 import mod2 but I'm getting an "Attempted relative import in non-package". I googled around but found only "sys.path manipulation" hacks. Isn't there a clean way? Edit: all my __init__.py's are currently empty Edit2: I'm trying to do this because sub2 contains classes that are shared across sub packages (sub1, subX, etc.). Edit3: The behaviour I'm looking for is the same as described in PEP 366 (thanks John B)

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• Employing elegance in order to evade importing elephants: a case of excessive dll Imports

  - by user994179

  I am writing C# code that interfaces to a legacy (Feb 2012) C program, using DllImport. It works fine, but I need to call more than 30 different functions, turning my normally impeccable, exquisite code into something of near-elephantine proportions. Surely there must be a way around this? [Warning: those with weak stomachs may want to avert their eyes from what follows]: [DllImport("C:\\Users\\mitt\\Documents\\Visual Studio 2010\\Projects\\mrSolution\\mr\\x64\\Debug\\mrDll.dll", CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)] public static extern bool mrEngine_initialize( [In, Out, MarshalAs(UnmanagedType.LPStruct)] PLOT_SPEC PlotSpec); [DllImport("C:\\Users\\mitt\\Documents\\Visual Studio 2010\\Projects\\mrSolution\\mr\\x64\\Debug\\mrDll.dll", CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)] public static extern bool mrEngine_getDataPoint( [In, Out, MarshalAs(UnmanagedType.LPStruct)] PLOT_SPEC PlotSpec);

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• Compiled Haskell libraries with FFI imports are invalid when imported into GHCI

  - by John Millikin

  I am using GHC 6.12.1, in Ubuntu 10.04 When I try to use the FFI syntax for static storage, only modules running in interpreted mode (ie GHCI) work properly. Compiled modules have invalid pointers, and do not work. I'd like to know whether anybody can reproduce the problem, whether this an error in my code or GHC, and (if the latter) whether it's a known issue. I'm using sys_siglist because it's present in a standard library on my system, but I don't believe the actual storage used matters (I discovered this while writing a binding to libidn). If it helps, sys_siglist is defined in <signal.h> as: extern __const char *__const sys_siglist[_NSIG]; I thought this type might be the problem, so I also tried wrapping it in a plain C procedure: #include<stdio.h> const char **test_ffi_import() { printf("C think sys_siglist = %X\n", sys_siglist); return sys_siglist; } However, importing that doesn't change the result, and the printf() call prints the same pointer value as show siglist_a. My suspicion is that it's something to do with static and dynamic library loading. Update: somebody in #haskell suggested this might be 64-bit specific; if anybody tries to reproduce it, can you mention your architecture and whether it worked in a comment? Code as follows: -- A.hs {-# LANGUAGE ForeignFunctionInterface #-} module A where import Foreign import Foreign.C foreign import ccall "&sys_siglist" siglist_a :: Ptr CString -- -- B.hs {-# LANGUAGE ForeignFunctionInterface #-} module B where import Foreign import Foreign.C foreign import ccall "&sys_siglist" siglist_b :: Ptr CString -- -- Main.hs {-# LANGUAGE ForeignFunctionInterface #-} module Main where import Foreign import Foreign.C import A import B foreign import ccall "&sys_siglist" siglist_main :: Ptr CString main = do putStrLn $ "siglist_a = " ++ show siglist_a putStrLn $ "siglist_b = " ++ show siglist_b putStrLn $ "siglist_main = " ++ show siglist_main peekSiglist "a " siglist_a peekSiglist "b " siglist_b peekSiglist "main" siglist_main peekSiglist name siglist = do ptr <- peekElemOff siglist 2 str <- maybePeek peekCString ptr putStrLn $ "siglist_" ++ name ++ "[2] = " ++ show str I would expect something like this output, where all pointer values identical and valid: $ runhaskell Main.hs siglist_a = 0x00007f53a948fe00 siglist_b = 0x00007f53a948fe00 siglist_main = 0x00007f53a948fe00 siglist_a [2] = Just "Interrupt" siglist_b [2] = Just "Interrupt" siglist_main[2] = Just "Interrupt" However, if I compile A.hs (with ghc -c A.hs), then the output changes to: $ runhaskell Main.hs siglist_a = 0x0000000040378918 siglist_b = 0x00007fe7c029ce00 siglist_main = 0x00007fe7c029ce00 siglist_a [2] = Nothing siglist_b [2] = Just "Interrupt" siglist_main[2] = Just "Interrupt"

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