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  • Is functional programming a superset of object oriented?

    - by Jimmy Hoffa
    The more functional programming I do, the more I feel like it adds an extra layer of abstraction that seems like how an onion's layer is- all encompassing of the previous layers. I don't know if this is true so going off the OOP principles I've worked with for years, can anyone explain how functional does or doesn't accurately depict any of them: Encapsulation, Abstraction, Inheritance, Polymorphism I think we can all say, yes it has encapsulation via tuples, or do tuples count technically as fact of "functional programming" or are they just a utility of the language? I know Haskell can meet the "interfaces" requirement, but again not certain if it's method is a fact of functional? I'm guessing that the fact that functors have a mathematical basis you could say those are a definite built in expectation of functional, perhaps? Please, detail how you think functional does or does not fulfill the 4 principles of OOP.

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  • Recommended reading for (Object Oriented) application design architecture?

    - by e4rthdog
    In life it doesnt matter if you do one thing for 15 years. You will end up waking one day and asking stuff that are equal to "how do i walk?" :) My specific question is that as a new entrant to C# and OOP i am stepping into many little "details" that need to be addressed. Written a lot of code in VB.NET / cobol / simple php e.t.c surely does not help much into the OOP world... So , even after reading entry level books for C# and watching some videos i recently found out about the "factory model design" for applications. I would appreciate if any of you guys recomment some reading on application design architecture for further reading...

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  • Newton Game Dynamics: Making an object not affect another object

    - by Boreal
    I'm going to be using Newton in my networked action game with Mogre. There will be two "types" of physics object: global and local. Global objects will be kept in sync for everybody; these include the players, projectiles, and other gameplay-related objects. Local objects are purely for effect, like ragdolls, debris, and particles. Is there a way to make the global objects affect the local objects without actually getting affected themselves? I'd like debris to bounce off of a tank, but I don't want the tank to respond in any way.

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  • Object inheritance and method parameters/return types - Please check my logic

    - by user2368481
    I'm preparing for a test and doing practice questions, this one in particular I am unsure I did correctly: We are given a very simple UML diagram to demonstrate inheritance: I hope this is clear, it shows that W inherits from V and so on: |-----Y V <|----- W<|-----| |-----X<|----Z and this code: public X method1(){....} method2(new Y()); method2(method1()); method2(method3()); The questions and my answers: Q: What types of objects could method1 actually return? A: X and Z, since the method definition includes X as the return type and since Z is a kind of X is would be OK to return either. Q: What could the parameter type of method2 be? A: Since method2 in the code accepts Y, X and Z (as the return from method1), the parameter type must be either V or W, as Y,X and Z inherit from both of these. Q: What could return type of method3 be? A: Return type of method3 must be V or W as this would be consistent with answer 2.

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  • Object construction design

    - by James
    I recently started to use c# to interface with a database, and there was one part of the process that appeared odd to me. When creating a SqlCommand, the method I was lead to took the form: SqlCommand myCommand = new SqlCommand("Command String", myConnection); Coming from a Java background, I was expecting something more similar to SqlCommand myCommand = myConnection.createCommand("Command String"); I am asking, in terms of design, what is the difference between the two? The phrase "single responsibility" has been used to suggest that a connection should not be responsible for creating SqlCommands, but I would also say that, in my mind, the difference between the two is partly a mental one of the difference between a connection executing a command and a command acting on a connection, the latter of which seems less like what I have been lead to believe OOP should be. There is also a part of me wondering if the two should be completely separate, and should only come together in some sort of connection.execute(command) method. Can anyone help clear up these differences? Are any of these methods "more correct" than the others from an OO point of view? (P.S. the fact that c# is used is completely irrelevant. It just highlighted to me that different approaches were used)

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  • Object desing problem for simple school application

    - by Aragornx
    I want to create simple school application that provides grades,notes,presence,etc. for students,teachers and parents. I'm trying to design objects for this problem and I'm little bit confused - because I'm not very experienced in class designing. Some of my present objects are : class PersonalData() { private String name; private String surename; private Calendar dateOfBirth; [...] } class Person { private PersonalData personalData; } class User extends Person { private String login; private char[] password; } class Student extends Person { private ArrayList<Counselor> counselors = new ArrayList<>(); } class Counselor extends Person { private ArrayList<Student> children = new ArrayList<>(); } class Teacher extends Person { private ArrayList<ChoolClass> schoolClasses = new ArrayList<>(); private ArrayList<Subject> subjects = new ArrayList<>(); } This is of course a general idea. But I'm sure it's not the best way. For example I want that one person could be a Teacher and also a Parent(Counselor) and present approach makes me to have two Person objects. I want that user after successful logging in get all roles that it has (Student or Teacher or (Teacher & Parent) ). I think I should make and use some interfaces but I'm not sure how to do this right. Maybe like this: interface Role { } interface TeacherRole implements Role { void addGrade( Student student, Grade grade, [...] ); } class Teacher implements TeacherRole { private Person person; [...] } class User extends Person{ ArrayList<Role> roles = new ArrayList<>(); } Please if anyone could help me to make this right or maybe just point me to some literature/article that covers practical objects design.

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  • Structuring Access Control In Hierarchical Object Graph

    - by SB2055
    I have a Folder entity that can be Moderated by users. Folders can contain other folders. So I may have a structure like this: Folder 1 Folder 2 Folder 3 Folder 4 I have to decide how to implement Moderation for this entity. I've come up with two options: Option 1 When the user is given moderation privileges to Folder 1, define a moderator relationship between Folder 1 and User 1. No other relationships are added to the db. To determine if the user can moderate Folder 3, I check and see if User 1 is the moderator of any parent folders. This seems to alleviate some of the complexity of handling updates / moved entities / additions under Folder 1 after the relationship has been defined, and reverting the relationship means I only have to deal with one entity. Option 2 When the user is given moderation privileges to Folder 1, define a new relationship between User 1 and Folder 1, and all child entities down to the grandest of grandchildren when the relationship is created, and if it's ever removed, iterate back down the graph to remove the relationship. If I add something under Folder 2 after this relationship has been made, I just copy all Moderators into the new Entity. But when I need to show only the top-level Folders that a user is Moderating, I need to query all folders that have a parent folder that the user does not moderate, as opposed to option 1, where I just query any items that the user is moderating. Thoughts I think it comes down to determining if users will be querying for all parent items more than they'll be querying child items... if so, then option 1 seems better. But I'm not sure. Is either approach better than the other? Why? Or is there another approach that's better than both? I'm using Entity Framework in case it matters.

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  • SQL SERVER – Error: Fix – Msg 208 – Invalid object name ‘dbo.backupset’ – Invalid object name ‘dbo.backupfile’

    - by pinaldave
    Just a day before I got a very interesting email. Here is the email (modified a bit to make it relevant to this blog post). “Pinal, We are facing a very strange issue. One of our query  related to backup files and backup set has stopped working suddenly in SSMS. It works fine in application where we have and in the stored procedure but when we have it in our SSMS it gives following error. Msg 208, Level 16, State 1, Line 1 Invalid object name ‘dbo.backupfile’. Here are our queries which we are trying to execute. SELECT name, database_name, backup_size, TYPE, compatibility_level, backup_set_id FROM dbo.backupset; SELECT logical_name, backup_size, file_type FROM dbo.backupfile; This query gives us details related to backupset and backup files when the backup was taken.” When I receive this kind of email, usually I have no answers directly. The claim that it works in stored procedure and in application but not in SSMS gives me no real data. I have requested him to very first check following two things: If he is connected to correct server? His answer was yes. If he has enough permissions? His answer was he was logged in as an admin. This means there was something more to it and I requested him to send me a screenshot of the his SSMS. He promptly sends that to me and as soon as I receive the screen shot I knew what was going on. Before I say anything take a look at the screenshot yourself and see if you can figure out why his queries are not working in SSMS. Just to make your life a bit easy, I have already given a hint in the image. The answer is very simple, the context of the database is master database. To execute above two queries the context of the database has to be msdb. Tables backupset and backupfile belong to the database msdb only. Here are two workaround or solution to above problem: 1) Change context to MSDB Above two queries when they will run as following they will not error out and will give the accurate desired result. USE msdb GO SELECT name, database_name, backup_size, TYPE, compatibility_level, backup_set_id FROM dbo.backupset; SELECT logical_name, backup_size, file_type FROM dbo.backupfile; 2) Prefix the query with msdb There are cases above script used in stored procedure or part of big query, it is not possible to change the context of the whole query to any specific database. Use three part naming convention and prefix them with msdb. SELECT name, database_name, backup_size, TYPE, compatibility_level, backup_set_id FROM msdb.dbo.backupset; SELECT logical_name, backup_size, file_type FROM msdb.dbo.backupfile; Very simple solution but sometime keeps people wondering for an answer. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Error Messages, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Seeking web-based FTP client for very large file upload

    - by Paul M. Nguyen
    I have looked around for these for some time... the limits imposed by the web server and/or the dynamic programming environment (e.g. PHP) are far too restrictive for the application I'm working on. We need to be able to move large graphics and video files to and from clients (ranging from tens of MB to a few GB in a single file). Plain FTP with a proper desktop client will do the trick, and we're hosting this in Amazon EC2 with EBS. User management will be done from the office via webmin. Users are chroot-jailed into their home dir by proftpd. net2ftp will work for many clients, but we often need to move single files that approach 1GB or exceed 2-3GB which is way out of the range of any http-based uploader. So we turn to Java or Flash - can they do it? From within the web browser establish an FTP connection and grab a huge file? There are licensed applets and such out there, but none seem convincing. Again, I'm looking for some code that can speak FTP and read (& write?) the local disk, that is delivered in a web browser, and can move single files of 2GB+. The reason for having a web-based interface to FTP is to skip the software installation step for our clients. I will consider proper desktop client software as long as it's "portable" and at least Win+Mac and can be easily configured by lay-man users in a hurry.

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  • copy large LVM volume(14TB) from one server to another

    - by bruce
    recently,I have to copy a very large LVM volume()rom server A to server B. Below is the filesystem of server A and server B - server A [root@AVDVD-Filer ~]# df -h Filesystem Size Used Avail Use% Mounted on /dev/mapper/vg_avdvdfiler-lv_root 16T 14T 1.5T 91% / tmpfs 3.0G 0 3.0G 0% /dev/shm /dev/cciss/c0d0p1 194M 23M 162M 13% /boot /dev/mapper/vg_avdvdfiler-test 2.3T 201M 2.1T 1% /test /dev/sr0 3.3G 3.3G 0 100% /mnt server B [root@localhost ~]# df -h Filesystem Size Used Avail Use% Mounted on /dev/mapper/VolGroup-LogVol00 20G 2.5G 16G 14% / tmpfs 3.0G 0 3.0G 0% /dev/shm /dev/cciss/c0d0p1 194M 23M 162M 13% /boot /dev/mapper/VolGroup00-LogVol00 16T 133M 15T 1% /xiangao/lv1 /dev/mapper/VolGroup00-LogVol01 4.7T 190M 4.5T 1% /xiangao/lv2 I want to copy LVM volume /dev/mapper/vg_avdvdfiler-lv_root on server A to LVM volume /dev/mapper/VolGroup00-LogVol00 on server B . The server A and server B is in the same IP segment. IN the LVM volume on server A , there is all average 500M avi wmv mp4 etc. I tried mount /dev/mapper/vg_avdvdfiler-lv_root on server A to server B through NFS , then use cp command copy. It is clear I faild . Because the LVM volume is too big , I do not have good idea . I hope a good solution here. I'm a chinese, my english is very pool. sorry thanks everyone!

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  • Where my memory is alloced, Stack or Heap, Can I find it at Run-time?

    - by AKN
    I know that memory alloced using new, gets its space in heap, and so we need to delete it before program ends, to avoid memory leak. Let's look at this program... Case 1: char *MyData = new char[20]; _tcscpy(MyData,"Value"); . . . delete[] MyData; MyData = NULL; Case 2: char *MyData = new char[20]; MyData = "Value"; . . . delete[] MyData; MyData = NULL; In case 2, instead of allocating value to the heap memory, it is pointing to a string literal. Now when we do a delete it would crash, AS EXPECTED, since it is not trying to delete a heap memory. Is there a way to know where the pointer is pointing to heap or stack? By this the programmer Will not try to delete any stack memory He can investigate why does this ponter, that was pointing to a heap memory initially, is made to refer local literals? What happened to the heap memory in the middle? Is it being made to point by another pointer and delete elsewhere and all that?

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  • Unable to migrate mail with large attachment upto 2 MB

    - by Preeti
    I am creating EML file with "System.Net.Mail".After that i am migrating it to Google Mail using google API ver 2. For small attachments it is working fine. But in case of large attachment upto (1 MB or 2 MB) it throwing exception "Request aborted". How can migrate mail with large file attachment? I got solution of sending large size attachment using System.Net.Mail. But how to implement it in case of Google apps? Thanx

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  • How to make an object stay relative to another object

    - by Nick
    In the following example there is a guy and a boat. They have both a position, orientation and velocity. The guy is standing on the shore and would like to board. He changes his position so he is now standing on the boat. The boat changes velocity and orientation and heads off. My character however has a velocity of 0,0,0 but I would like him to stay onboard. When I move my character around, I would like to move as if the boat was the ground I was standing on. How do keep my character aligned properly with the boat? It is exactly like in World Of Warcraft, when you board a boat or zeppelin. This is my physics code for the guy and boat: this.velocity.addSelf(acceleration.multiplyScalar(dTime)); this.position.addSelf(this.velocity.clone().multiplyScalar(dTime)); The guy already has a reference to the boat he's standing on, and thus knows the boat's position, velocity, orientation (even matrices or quaternions can be used).

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  • How to play the sound of an object sliding on another object for a variable duration

    - by Antoine
    I would like to add sound effects to a basic 2D game. For example, a stone sphere is rolling on wood surface. Let's say I have a 2 second audio recording of this. How could I use the sample to add sound for an arbitrary duration ? So far I have two solutions in mind: a/ record the sound for an amount of time that is greater than the maximum expected duration, and play only a part of it; b/ extract a small portion of the sample and play it in a loop for the duration of the move; however I'm not sure if it makes sense with an audio wave.

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  • Breaking up a large PHP object used to abstract the database. Best practices?

    - by John Kershaw
    Two years ago it was thought a single object with functions such as $database->get_user_from_id($ID) would be a good idea. The functions return objects (not arrays), and the front-end code never worries about the database. This was great, until we started growing the database. There's now 30+ tables, and around 150 functions in the database object. It's getting impractical and unmanageable and I'm going to be breaking it up. What is a good solution to this problem? The project is large, so there's a limit to the extent I can change things. My current plan is to extend the current object for each table, then have the database object contain these. So, the above example would turn into (assume "user" is a table) $database->user->get_user_from_id($ID). Instead of one large file, we would have a file for every table.

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  • In windbg, how do I get a heap header address from !heap -l results?

    - by Kevin
    I am playing around with windbg's !heap command, particular the "-l" switch which detects memory leaks. When -l does detect a leak, I am having problems navigating from its results to a stack trace for the source of the leak. Here is a snippet of the results from !heap -l 0:066 !heap -l Searching the memory for potential unreachable busy blocks. Entry User Heap Segment Size PrevSize Unused Flags 0324b500 0324b508 01580000 03230000 20 60 a busy 0324b520 0324b528 01580000 03230000 20 20 a busy 0324b5c8 0324b5d0 01580000 03230000 20 28 a busy Windbg's documentation for !heap tells me to use dt _DPH_BLOCK_INFORMATION with the header address, followed by dds with the blocks' StackTrace field. But the output for !heap -l doesn't specify a header address! It's only specififying Entry, User, Heap, and Segment. I've racked my brain looking over the other commands but can't figure out how to get the header address from any of these fields. Can someone help?

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  • Significant amount of the time, I can't think of a reason to have an object instead of a static class. Do objects have more benefits than I think?

    - by Prog
    I understand the concept of an object, and as a Java programmer I feel the OO paradigm comes rather naturally to me in practice. However recently I found myself thinking: Wait a second, what are actually the practical benefits of using an object over using a static class (with proper encapsulation and OO practices)? I could think of two benefits of using an object (both significant and powerful): Polymorphism: allows you to swap functionality dynamically and flexibly during runtime. Also allows to add new functionality 'parts' and alternatives to the system easily. For example if there's a Car class designed to work with Engine objects, and you want to add a new Engine to the system that the Car can use, you can create a new Engine subclass and simply pass an object of this class into the Car object, without having to change anything about Car. And you can decide to do so during runtime. Being able to 'pass functionality around': you can pass an object around the system dynamically. But are there any more advantages to objects over static classes? Often when I add new 'parts' to a system, I do so by creating a new class and instantiating objects from it. But recently when I stopped and thought about it, I realized that a static class would do just the same as an object, in a lot of the places where I normally use an object. For example, I'm working on adding a save/load-file mechanism to my app. With an object, the calling line of code will look like this: Thing thing = fileLoader.load(file); With a static class, it would look like this: Thing thing = FileLoader.load(file); What's the difference? Fairly often I just can't think of a reason to instantiate an object when a plain-old static-class would act just the same. But in OO systems, static classes are fairly rare. So I must be missing something. Are there any more advantages to objects other from the two that I listed? Please explain.

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  • Ubuntu 12.4 - Terminal - Huge/Large text on each command line [closed]

    - by gotqn
    Possible Duplicate: Is it possible to change my terminal window prompt text? I have been using "Ubuntu 12.4" for few days now (no previous Linux experiences at all) and I have noticed that the symbols on each command line more then this in many examples in the network. For example, I have: And I want to remove the "gotqn-System-Product-Name" part, because it is taking too much space? What should I do to change this?

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  • OOP concept: is it possible to update the class of an instantiated object?

    - by Federico
    I am trying to write a simple program that should allow a user to save and display sets of heterogeneous, but somehow related data. For clarity sake, I will use a representative example of vehicles. The program flow is like this: The program creates a Garage object, which is basically a class that can contain a list of vehicles objects Then the users creates Vehicles objects, these Vehicles each have a property, lets say License Plate Nr. Once created, the Vehicle object get added to a list within the Garage object --Later on--, the user can specify that a given Vehicle object is in fact a Car object or a Truck object (thus giving access to some specific attributes such as Number of seats for the Car, or Cargo weight for the truck) At first sight, this might look like an OOP textbook question involving a base class and inheritance, but the problem is more subtle because at the object creation time (and until the user decides to give more info), the computer doesn't know the exact Vehicle type. Hence my question: how would you proceed to implement this program flow? Is OOP the way to go? Just to give an initial answer, here is what I've came up until now. There is only one Vehicle class and the various properties/values are handled by the main program (not the class) through a dictionary. However, I'm pretty sure that there must be a more elegant solution (I'm developing using VB.net): Public Class Garage Public GarageAdress As String Private _ListGarageVehicles As New List(Of Vehicles) Public Sub AddVehicle(Vehicle As Vehicles) _ListGarageVehicles.Add(Vehicle) End Sub End Class Public Class Vehicles Public LicensePlateNumber As String Public Enum VehicleTypes Generic = 0 Car = 1 Truck = 2 End Enum Public VehicleType As VehicleTypes Public DictVehicleProperties As New Dictionary(Of String, String) End Class NOTE that in the example above the public/private modifiers do not necessarily reflect the original code

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  • Too many heap subpools might break the upgrade

    - by Mike Dietrich
    Recently one of our new upcoming Oracle Database 11.2 reference customers did upgrade their production database - a huge EBS system - from Oracle 9.2.0.8 to Oracle Database 11.2.0.2. They've tested very well, we've optimized the upgrade process, the recompilation timings etc.  But once the live upgrade was done it did fail in the JAVA component piece with this error: begin if initjvmaux.startstep('CREATE_JAVA_SYSTEM') then * ORA-29553: classw in use: SYS.javax/mail/folder ORA-06512: at "SYS.INITJVMAUX", line 23 ORA-06512: at line 5 Support diagnosis was pretty quick - and refered to:Bug 10165223 - ORA-29553: class in use: sys.javax/mail/folder during database upgrade But how could this happen? Actually I don't know as we have used the same init.ora setup on test and production. The only difference: the prod system has more CPUs and RAM. Anyway, the bug names as workarounds to either decrease the SGA to less than 1GB or decrease the number of heap subpools to 1. Finally this query did help to diagnose the number of heap subpools: select count(distinct kghluidx) num_subpools from x$kghlu where kghlushrpool = 1; The result was 2 - so we did run the upgrade now with this parameter set: _kghdsidx_count=1 And finally it did work well. One sad thing:After the upgrade did fail Support did recommend to restore the whole database - which took an additional 3-4 hours. As the ORACLE SERVER component has been already upgraded successfully at the stage where the error did happen it would have been fine to go on with the manual upgrade and start catupgrd.sql script. It would have been detected that the ORACLE SERVER is upgraded already and just picked up the non-upgraded components. The good news:Finally I had one extra slide to add to our workshop presentation

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  • AS3 Working With Arbitrarily Large Files

    - by Kekoa
    I am trying to read a very large file in AS3 and am having problems with the runtime just crashing on me. I'm currently using a FileStream to open the file asynchronously. This does not work(crashes without an Exception) for files bigger than about 300MB. _fileStream = new FileStream(); _fileStream.addEventListener(IOErrorEvent.IO_ERROR, loadError); _fileStream.addEventListener(Event.COMPLETE, loadComplete); _fileStream.openAsync(myFile, FileMode.READ); In looking at the documentation, it sounds like the FileStream class still tries to read in the entire file to memory(which is bad for large files). Is there a more suitable class to use for reading large files? I really would like something like a buffered FileStream class that only loads the bytes from the files that are going to be read next. I'm expecting that I may need to write a class that does this for me, but then I would need to read only a piece of a file at a time. I'm assuming that I can do this by setting the position and readAhead properties of the FileStream to read a chunk out of a file at a time. I would love to save some time if there is a class like this that already exists. Is there a good way to process large files in AS3, without loading entire contents into memory?

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  • Save object using variable with object name

    - by FBE
    I'm wondering what an easy way is to save an object in R, using a variable objectName with the name of the object to be saved. I want this to easy save objects, with their name in the file name. I tried to use get, but I didn't manage to save the object with it's original object name. Example: If I have the object called "temp", which I want to save in the directory "dataDir". I put the name of the object in the variable "objectName". Attempt 1: objectName<-"temp" save(get(objectName), file=paste(dataDir, objectName, ".RData", sep="")) load(paste(dataDir, objectName, ".RData", sep="")) This didn't work, because R tries to save an object called get(objectName), instead of the result of this call. So I tried the following: Attempt 2: objectName<-"temp" object<-get(objectName) save(object, file=paste(dataDir, objectName, ".RData", sep="")) load(paste(dataDir, objectName, ".RData", sep="")) This obviously didn't work, because R saves the object with name "object", and not with name "temp". After loading I have a copy of "object", instead of "temp". (Yes, with the same contents...but that is not what I want :) ). So I thought it should be something with pointers. So tried the following: Attempt 3: objectName<-"temp" object<<-get(objectName) save(object, file=paste(dataDir, objectName, ".RData", sep="")) load(paste(dataDir, objectName, ".RData", sep="")) Same result as attempt 2. But I'm not sure I'm doing what I think I'm doing. What is the solution for this?

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  • Getting the start address of the current process's heap?

    - by beta
    Hey, I am exploring the lower level workings of the system, and was wondering how malloc determines the start address of the heap. Is the heap a constant offset or is there a call of some sort to get the start address? Does the stack effect the start address of the heap? Thanks, Braden McDorman

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