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  • Why do I have to specify pure virtual functions in the declaration of a derived class in Visual C++?

    - by neuviemeporte
    Given the base class A and the derived class B: class A { public: virtual void f() = 0; }; class B : public A { public: void g(); }; void B::g() { cout << "Yay!"; } void B::f() { cout << "Argh!"; } I get errors saying that f() is not declared in B while trying do define void B::f(). Do I have to declare f() explicitly in B? I think that if the interface changes I shouldn't have to correct the declarations in every single class deriving from it. Is there no way for B to get all the virtual functions' declarations from A automatically? EDIT: I found an article that says the inheritance of pure virtual functions is dependent on the compiler: http://www.objectmentor.com/resources/articles/abcpvf.pdf I'm using VC++2008, wonder if there's an option for this.

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  • Problem with number/type of arguments passed to an overloaded c++ constructor wrapped with swig.

    - by MiKo
    I am trying to wrap a c++ class (let's call it "Spam") written by someone else with swig to expose it to Python. After solving several problems, I am able to import the module in python, but when I try to create an object of such class I obtain the following error: foo = Spam.Spam('abc',3) Traceback (most recent call last): File "<stdin>", line 1, in <module> File "Spam.py", line 96, in __init__ this = _Spam.new_Spam(*args) NotImplementedError: Wrong number of arguments for overloaded function 'new_Spam'. Possible C/C++ prototypes are: Spam(unsigned char *,unsigned long,bool,unsigned int,SSTree::io_action,char const *) Spam(unsigned char *,unsigned long,bool,unsigned int,SSTree::io_action) Spam(unsigned char *,unsigned long,bool,unsigned int) Spam(unsigned char *,unsigned long,bool) Spam(unsigned char *,unsigned long) Googling around, I realized that the error is probably caused by the type of the arguments and not by the number (which is quite confusing), but I still cannot identify. I suspect the problem lies in passing a string as the first argument, but have no idea on how to fix it (keep in mind that I know almost no c/c++).

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  • How much does an InnoDB table benefit from having fixed-length rows?

    - by Philip Eve
    I know that dependent on the database storage engine in use, a performance benefit can be found if all of the rows in the table can be guaranteed to be the same length (by avoiding nullable columns and not using any VARCHAR, TEXT or BLOB columns). I'm not clear on how far this applies to InnoDB, with its funny table arrangements. Let's give an example: I have the following table CREATE TABLE `PlayerGameRcd` ( `User` SMALLINT UNSIGNED NOT NULL, `Game` MEDIUMINT UNSIGNED NOT NULL, `GameResult` ENUM('Quit', 'Kicked by Vote', 'Kicked by Admin', 'Kicked by System', 'Finished 5th', 'Finished 4th', 'Finished 3rd', 'Finished 2nd', 'Finished 1st', 'Game Aborted', 'Playing', 'Hide' ) NOT NULL DEFAULT 'Playing', `Inherited` TINYINT NOT NULL, `GameCounts` TINYINT NOT NULL, `Colour` TINYINT UNSIGNED NOT NULL, `Score` SMALLINT UNSIGNED NOT NULL DEFAULT 0, `NumLongTurns` TINYINT UNSIGNED NOT NULL DEFAULT 0, `Notes` MEDIUMTEXT, `CurrentOccupant` TINYINT UNSIGNED NOT NULL DEFAULT 0, PRIMARY KEY (`Game`, `User`), UNIQUE KEY `PGR_multi_uk` (`Game`, `CurrentOccupant`, `Colour`), INDEX `Stats_ind_PGR` (`GameCounts`, `GameResult`, `Score`, `User`), INDEX `GameList_ind_PGR` (`User`, `CurrentOccupant`, `Game`, `Colour`), CONSTRAINT `Constr_PlayerGameRcd_User_fk` FOREIGN KEY `User_fk` (`User`) REFERENCES `User` (`UserID`) ON DELETE CASCADE ON UPDATE CASCADE, CONSTRAINT `Constr_PlayerGameRcd_Game_fk` FOREIGN KEY `Game_fk` (`Game`) REFERENCES `Game` (`GameID`) ON DELETE CASCADE ON UPDATE CASCADE ) ENGINE=INNODB CHARACTER SET utf8 COLLATE utf8_general_ci The only column that is nullable is Notes, which is MEDIUMTEXT. This table presently has 33097 rows (which I appreciate is small as yet). Of these rows, only 61 have values in Notes. How much of an improvement might I see from, say, adding a new table to store the Notes column in and performing LEFT JOINs when necessary?

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  • C++ is there a difference between assignment inside a pass by value and pass by reference function?

    - by Rémy DAVID
    Is there a difference between foo and bar: class A { Object __o; void foo(Object& o) { __o = o; } void bar(Object o) { __o = o; } } As I understand it, foo performs no copy operation on object o when it is called, and one copy operation for assignment. Bar performs one copy operation on object o when it is called and another one for assignment. So I can more or less say that foo uses 2 times less memory than bar (if o is big enough). Is that correct ? Is it possible that the compiler optimises the bar function to perform only one copy operation on o ? i.e. makes __o pointing on the local copy of argument o instead of creating a new copy?

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  • Beginning android: how to map a string to a list

    - by user569421
    I just finished the NotepadV1-3 tutorial for Android apps, and I was thinking of creating my own inventory app for fun, which for now basically consists of a list of names (such as "DVD" or "Grocery"), each of which can be clicked, which will bring up another specific list associated with that name. However, with the SQLiteDatabase.insert(..) method, the ContentValue can only take (among many others) "String, String" as argument, and I can't figure out how to input into the database a list of Strings associated with a particular key. I'm having trouble researching on how to resolve this as I am not that familiar with SQL. What would be the best way to store a key with its associated list of Strings? Any pointers and suggestions are appreciated! Android newb :[

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  • ActiveModel::MassAssignmentSecurity::Error in CustomersController#create (attr_accessible is set)

    - by megabga
    In my controller, I've got error when create action and try create model [can't mass-assignment], but in my spec, my test of mass-assignment model its pass!?! My Model: class Customer < ActiveRecord::Base attr_accessible :doc, :doc_rg, :name, :birthday, :name_sec, :address, :state_id, :city_id, :district_id, :customer_pj, :is_customer, :segment_id, :activity_id, :person_type, :person_id belongs_to :person , :polymorphic => true, dependent: :destroy has_many :histories has_many :emails def self.search(search) if search conditions = [] conditions << ['name LIKE ?', "%#{search}%"] find(:all, :conditions => conditions) else find(:all) end end end I`ve tired set attr_accessible in controller too, in my randomized way. the Controller: class CustomersController < ApplicationController include ActiveModel::MassAssignmentSecurity attr_accessible :doc, :doc_rg, :name, :birthday, :name_sec, :address, :state_id, :city_id, :district_id, :customer_pj, :is_customer autocomplete :business_segment, :name, :full => true autocomplete :business_activity, :name, :full => true [...] end The test, my passed test describe "accessible attributes" do it "should allow access to basics fields" do expect do @customer.save end.should_not raise_error(ActiveModel::MassAssignmentSecurity::Error) end end The error: ActiveModel::MassAssignmentSecurity::Error in CustomersController#create Can't mass-assign protected attributes: doc, doc_rg, name_sec, address, state_id, city_id, district_id, customer_pj, is_customer https://github.com/megabga/crm 1.9.2p320 Rails 3.2 MacOS pg

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  • GUID.TryParse() ?

    - by Jack Marchetti
    Obviously there is no public GUID.TryParse() in .NET CLR 2.0. So, I was looking into regular expressions [aka googling around to find one] and each time I found one there was a heated argument in the comments section about RegEx A doesn't work, use RegEx B. Then someone would write Regex C yadda yadda So anyway, What I decided to do was this, but I feel bad about it. public static bool IsGuid (string possibleGuid) { try { Guid gid = new Guid(possibleGuid); return true; } catch (Exception ex) { return false; } } Obviously I don't really like this since it's been drilled into me since day one to avoid throwing exceptions if you can defensibly code around it. Does anyonek now why there is no public Guid.TryParse() in the .NET Framework? Does anyone have a real Regular Expression that will work for all GUIDs?

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  • Unsigneds in order to prevent negative numbers

    - by Bruno Brant
    let's rope I can make this non-sujective Here's the thing: Sometimes, on fixed-typed languages, I restrict input on methods and functions to positive numbers by using the unsigned types, like unsigned int or unsigned double, etc. Most libraries, however, doesn't seem to think that way. Take C# string.Length. It's a integer, even though it can never be negative. Same goes for C/C++: sqrt input is an int or a double. I know there are reasons for this ... for example your argument might be read from a file and (no idea why) you may prefer to send the value directly to the function and check for errors latter (or use a try-catch block). So, I'm assuming that libraries are way better designed than my own code. So what are the reasons against using unsigned numbers to represent positive numbers? It's because of overflow when we cast then back to signed types?

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  • Drupal - Views + node preview woes

    - by Ace
    Hey there! I have a few Views on my Drupal 6 site which take care of some of a node's fields. For example, I have a content type called Country, which has a field called Capital. I've excluded this field in the node display, but there is a view that takes the node ID as an argument and displays it in the right column. This is all very pretty and has been working out well for me, but how do I take care of the node preview mode? Since the node isn't saved yet, the Capital field won't have its new value yet. Note: I am ready to do some very dirty hacks to make this work :)

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  • Undefined method for a belongs_to association

    - by marimaf
    My code: class User < ActiveRecord::Base belongs_to :university end class University < ActiveRecord::Base has_many :users, dependent: :destroy end and my model User has a university_id attribute. If I do University.find(1).users I get the list of users, but if I do User.find(1).university (and I checked that university_id is not nil here) I get: NoMethodError: undefined method `university' for from /home/mari/.rvm/gems/ruby-1.9.2-p290/gems/activemodel-3.0.10/lib/active_model/attribute_methods.rb :392:in `method_missing' from /home/mari/.rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.0.10/lib/active_record/attribute_methods. rb:46:in `method_missing' from (irb):14 from /home/mari/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.0.10/lib/rails/commands/console.rb:44:in sta rt' from /home/mari/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.0.10/lib/rails/commands/console.rb:8:in star t' from /home/mari/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.0.10/lib/rails/commands.rb:23:in <top (requi red)>' from script/rails:6:inrequire' from script/rails:6:in `' What am I doing wrong? I have another models and they are working just fine. Any suggestions? Thanks in advance

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  • Advice: Python Framework Server/Worker Queue management (not Website)

    - by Muppet Geoff
    I am looking for some advice/opinions of which Python Framework to use in an implementation of multiple 'Worker' PCs co-ordinated from a central Queue Manager. For completeness, the 'Worker' PCs will be running Audio Conversion routines (which I do not need advice on, and have standalone code that works). The Audio conversion takes a long time, and I need to co-ordinate an arbitrary number of the 'Workers' from a central location, handing them conversion tasks (such as where to get the source files, or where to ask for the job configuration) with them reporting back some additional info, such as the runtime of the converted audio etc. At present, I have a script that makes a webservice call to get the 'configuration' for a conversion task, based on source files located on the worker already (we manually copy the source files to the worker, and that triggers a conversion routine). I want to change this, so that we can distribute conversion tasks ("Oy you, process this: xxx") based on availability, and in an ideal world, based on pending tasks too. There is a chance that Workers can go offline mid-conversion (but this is not likely). All the workers are Windows based, the co-ordinator can be WIndows or Linux. I have (in my initial searches) come across the following - and I know that some are cross-dependent: Celery (with RabbitMQ) Twisted Django Using a framework, rather than home-brewing, seems to make more sense to me right now. I have a limited timeframe in which to develop this functional extension. An additional consideration would be using a Framework that is compatible with PyQT/PySide so that I can write a simple UI to display Queue status etc. I appreciate that the specifics above are a little vague, and I hope that someone can offer me a pointer or two. Again: I am looking for general advice on which Python framework to investigate further, for developing a Server/Worker 'Queue management' solution, for non-web activities (this is why DJango didn't seem the right fit).

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  • What is wrong in this json string?

    - by bala3569
    My json string looks like this, {"id" : "38","heading" : "Can you also figure out how to get me back the 10 hours I sp.....","description" : "Im having a very similar problem with the Login control - again it always generates a default style containing border -collapse -only in this case .....","img_url" : "~/EventImages/ EventImages1274014884460.jpg","catogory" : "News","doe" : "15-05-2010 "} But get the error, unterminated string literal.... EDIT: I used this but it didn't work, var newjson = cfreturn( """" & ToString( HfJsonValue ).ReplaceAll( "(['""\\\/\n\r\t]{1})", "\\$1" ) & """" ) ; var jsonObj = eval('(' + newjson + ')'); Error: missing ) after argument list Source Code: var newjson = cfreturn( """" & ToString( HfJsonValue ).ReplaceAll( "(['""\\\/\n\r\t]{1})", "\\$1" ) & """" ) ;

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  • Dimension Reduction in Categorical Data with missing values

    - by user227290
    I have a regression model in which the dependent variable is continuous but ninety percent of the independent variables are categorical(both ordered and unordered) and around thirty percent of the records have missing values(to make matters worse they are missing randomly without any pattern, that is, more that forty five percent of the data hava at least one missing value). There is no a priori theory to choose the specification of the model so one of the key tasks is dimension reduction before running the regression. While I am aware of several methods for dimension reduction for continuous variables I am not aware of a similar statical literature for categorical data (except, perhaps, as a part of correspondence analysis which is basically a variation of principal component analysis on frequency table). Let me also add that the dataset is of moderate size 500000 observations with 200 variables. I have two questions. Is there a good statistical reference out there for dimension reduction for categorical data along with robust imputation (I think the first issue is imputation and then dimension reduction)? This is linked to implementation of above problem. I have used R extensively earlier and tend to use transcan and impute function heavily for continuous variables and use a variation of tree method to impute categorical values. I have a working knowledge of Python so if something is nice out there for this purpose then I will use it. Any implementation pointers in python or R will be of great help. Thank you.

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  • What is the fastest way to get the persisted object after calling Hibernate's saveOrUpdate?

    - by Dave
    I'm using Hibernate 3.2.1.ga, hibernate annotations 3.2.1.ga, and hibernate-jpa-2.0-api. I can't upgrade at this time as I'm working with legacy code. I have this generic method for saving or updating objects ... protected void saveOrUpdate(Object obj) { final Session session = sessionFactory.getCurrentSession(); session.saveOrUpdate(obj); } You can assume that every argument, "obj," will have a member field that is marked with the "@Id" annotation. I would like to change the return type to return an Object that represents the persisted object in the database (meaning if "obj" didn't contain an id before, what is returned is the database object with a populated id. What is the fastest way to do this given my versioning and generic constraints?

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  • Inline function v. Macro in C -- What's the Overhead (Memory/Speed)?

    - by Jason R. Mick
    I searched Stack Overflow for the pros/cons of function-like macros v. inline functions. I found the following discussion: Pros and Cons of Different macro function / inline methods in C ...but it didn't answer my primary burning question. Namely, what is the overhead in c of using a macro function (with variables, possibly other function calls) v. an inline function, in terms of memory usage and execution speed? Are there any compiler-dependent differences in overhead? I have both icc and gcc at my disposal. My code snippet I'm modularizing is: double AttractiveTerm = pow(SigmaSquared/RadialDistanceSquared,3); double RepulsiveTerm = AttractiveTerm * AttractiveTerm; EnergyContribution += 4 * Epsilon * (RepulsiveTerm - AttractiveTerm); My reason for turning it into an inline function/macro is so I can drop it into a c file and then conditionally compile other similar, but slightly different functions/macros. e.g.: double AttractiveTerm = pow(SigmaSquared/RadialDistanceSquared,3); double RepulsiveTerm = pow(SigmaSquared/RadialDistanceSquared,9); EnergyContribution += 4 * Epsilon * (RepulsiveTerm - AttractiveTerm); (note the difference in the second line...) This function is a central one to my code and gets called thousands of times per step in my program and my program performs millions of steps. Thus I want to have the LEAST overhead possible, hence why I'm wasting time worrying about the overhead of inlining v. transforming the code into a macro. Based on the prior discussion I already realize other pros/cons (type independence and resulting errors from that) of macros... but what I want to know most, and don't currently know is the PERFORMANCE. I know some of you C veterans will have some great insight for me!!

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  • PHP: documentElemnt->childNodes warning

    - by jun
    $xml = file_get_contents(example.com); $dom = new DomDocument(); $dom->loadXML($xml); $items = $dom->documentElement; foreach($items->childNodes as $item) { $childs = $item->childNodes; foreach($childs as $i) { echo $i->nodeValue . "<br />"; } } Now I get this warning in every 2nd foreach: Warning: Invalid argument supplied for foreach() in file_example.php on line 14 Please help guys. Thanks!

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  • Reflection: How to get the underlying type of a by-ref type

    - by Qwertie
    I was surprised to learn that "ref" and "out" parameters are not marked by a special attribute, despite the existence of ParameterInfo.IsOut, ParameterInfo.IsIn (both of which are always false as far as I can see), ParameterAttributes.In and ParameterAttributes.Out. Instead, "ref" parameters are actually represented by a special kind of "Type" object and "out" parameters are just ref parameters with an additional attribute (what kind of attribute I don't yet know). Anyway, to make a by-ref argument you call Type.MakeByRefType(), but my question is, if you already have a by-ref type, how do you get back to the original Type? Hint: it's not UnderlyingSystemType: Type t = typeof(int); Console.WriteLine(t.MakeByRefType().UnderlyingSystemType==t); // FALSE

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  • Function calls in virtual machine killing performance

    - by GenTiradentes
    I wrote a virtual machine in C, which has a call table populated by pointers to functions that provide the functionality of the VM's opcodes. When the virtual machine is run, it first interprets a program, creating an array of indexes corresponding to the appropriate function in the call table for the opcode provided. It then loops through the array, calling each function until it reaches the end. Each instruction is extremely small, typically one line. Perfect for inlining. The problem is that the compiler doesn't know when any of the virtual machine's instructions are going to be called, as it's decided at runtime, so it can't inline them. The overhead of function calls and argument passing is killing the performance of my VM. Any ideas on how to get around this?

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  • Escaping and unescaping a string with single and double quotes in Javascript

    - by Reina
    I have a search box that a user can search for any string including single AND double quotes, once they have searched, the backend is passing the keyword back to me so I can put it back in the box. I don't know what the string is so I can't escape quotes myself, below is an example: var keyword = "hello"; $("#selectionkeywords").val(); The issue I am having is that if the user enters "hello" the keyword becomes ""hello"" and I get this error: missing ) after argument list [Break On This Error] jQuery("#selectionkeywords").val(""hello""); The user could also enter single quotes so that rules it out as well. I tried using escape unescape but I still have the same issue e.g. escape(""hello"") I could get the value in an unescaped format e.g. "hello" but I don't know what to do with it, escape doesn't work on it I end up with this %26%23034%3Bhello%26%23034%3B So I'm pretty much stuck at the moment as I can't do anything to the string, any ideas?

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  • Don't understand multiple parameter declarations in objective-c

    - by Blankman
    can someone clarify this for me: When there’s more than one argument, the arguments are declared within the method name after the colons. Arguments break the name apart in the declaration, just as in a message. For example: - (void)setWidth:(float)width height:(float)height; So in the above: method is for instance variables returns void parameter#1 is a float, named width. parameter#2 is a float,named height. But why is it hieght:(float)height; and not just: - (void)setWidth: (float)width (float)height;

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  • "Abstract static" method - how?

    - by polyglot
    There are already several SO questions on why there is not abstract static method/field as such, but I'm wondering about how one would go about implementing the following psuedo-code: class Animal { abstract static int getNumberOfLegs(); // not possible } class Chicken inherits Animal { static int getNumberOfLegs() { return 2; } class Dog inherits Animal { static int getNumberOfLegs() { return 4; } Here is the problem: Assuming that I want make sure that every class that inherits Animal to contain getNumberOfLegs() method (i.e. almost like an interface, except I do want the abstract class to implement several methods that are common to all child classes, hence pure interface does not work here). getNumberOfLegs() obviously should be a static method (assuming that in a perfect world we dont' have crippled chicken and dogs so getNumberOfLegs is not instance-dependent). Without an "abstract static" method/field, one can either leave the method out from Animal class, then there is the risk that some child class do not have that method. Or one can make getNumberOfLegs an instance method, but then one would have to instantiate a class to find out how many legs that animal has - even though it is not necessary. How do one usually go about implementing this situation?

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  • A $_GET input paramter that's an Array

    - by donpal
    I'm trying to pass 3 parameter to a script, where the 3rd parameter $_GET['value3'] is supposed to be an array $_GET['value1'] $_GET['value2'] $_GET['value3'] //an array of items I'm calling the script like this: (notice my syntax for value3, I'm not sure it's correct) http://localhost/test.php?value1=test1&value2=test2&value3=[the, array, values] I then use a foreach to hopefully loop through the third parameter value3 which is the array //process the first input $_GET['value1'] //process the second input $_GET['value2'] //process the third input $_GET['value3'] which is the array foreach($_GET['value3'] as $arrayitem){ echo $arrayitem; } but I get the error Invalid argument supplied for foreach() I'm not sure if my methodology is correct. Can some clarify how you'd go about doing the sort of thing

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  • django-haystack urlpatterns include('haystack.urls') where does it lead to?

    - by Eugene
    I've recently begun to learn/install django/haystack/solr. Following the tutorial given in haystack site, I have urlpatterns = pattern('', r'^search/', include('haystack.urls')) I found haystack installed in /usr/local/lib/python2.6/dist-packages/haystack and located urls.py there. It has urlpatterns=patterns('haystack.views', url(r'^$', SearchView(), name='haystack_search'),) I thought the second argument of url() should be callable object. I looked at the views.py and SearchView is a class. What is going on here? What's get called eventually?

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  • Remove objects from different environments

    - by Fred
    I have an R script file that executes a second R script via: source("../scripts/second_file.R") That second file has the following lines: myfiles <- list.files(".",pattern = "*.csv") ... rm(myfiles) When I run the master R file I get: > source("../scripts/second_file.R") Error in file.remove(myfiles) : object 'myfiles' not found and the program aborts. I think this has something to do with the environment. I looked at ?rm() pages but less than illuminating. I figure I have to give it a position argument, but not sure which.

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  • Can not recognize pdf scanned page with greek words by using PB , EZTWAIN and TOCR 3.0

    - by sgian76
    Hi, Iam using PB 10.5.2 and EZTwain 3.30.0.28, XDefs 1.36b1 by Dosadi for scanning. Also Iam using the TOCR 3.0 for OCR management. In a function we use the following among all others : ... Long ll_acquire (as_path_filename is a function argument) ... ... TWAIN_SetAutoOCR(1) ll_acquire = TWAIN_AcquireMultipageFile(0, as_path_filename) the problem is that the scanned pdf page has latin (english) and greek words. The English characters are searched quite precisely but the greek don't at all. Do you think this that this has to do with the TOCR software. I just want to search AND for greek words Thanks in advance

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