Thank you, this helped me out immensely
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Programming |OT| C is better than C++! No, C++ is better than C
- Thread starter Kikarian
- Start date
Thank you, this helped me out immensely
AbortedWalrusFetus
Member
Any of you guys know anything about search?
I'm working on a project using Cassandra as the database at the moment. It's a simple social network type of thing. I am at the point where I need to implement a basic search for users and I know Cassandra/bigtable is just completely incapable of doing this. Anyone know what the best solution for this sort of thing is? I did some research and it seems that apache lucene and solr seem to be the tools for the job, but they seem really overkill for a simple user search. As of right now my decision has been to use MySQL to just do some basic index tables and then use a levenshtein distance function to get some basic results.
I'm working on a project using Cassandra as the database at the moment. It's a simple social network type of thing. I am at the point where I need to implement a basic search for users and I know Cassandra/bigtable is just completely incapable of doing this. Anyone know what the best solution for this sort of thing is? I did some research and it seems that apache lucene and solr seem to be the tools for the job, but they seem really overkill for a simple user search. As of right now my decision has been to use MySQL to just do some basic index tables and then use a levenshtein distance function to get some basic results.
Postgres full text search is actually quite good, and built into the database. I'd use that if you just want to get something up and running (assuming you have full control over your stack). I wouldn't recommend MySQL for new projects (it does have builtin FTS but it's not very good, same with SQL Server in this case). Curious whether you really need Cassandra--most of the time it's overkill.
Hey guys, I'm learning mySQL and need help with foreign keys. Say there is two tables members and groups linked with a bridge table members_groups. The only things in the members_groups table is member_id and group_id (the primary keys the two other tables). I'm supposed to write a script that creates the members_groups table, but I'm stuck on how to do foreign keys.
Would it be something like :
Would it be something like :
Code:
CREATE TABLE members_group (
member_id INT REFERENCES members (member_id),
group_id INT REFERENCES groups (group_ID)
);AbortedWalrusFetus
Member
I'll take a look at postgres, but at this point I don't really need the full text search, just some fuzzy lookups of names. If it has better builtin search than MySQL though it could be worth investigating.
As far as why Cassandra, I'm coding this as a startup. I'm actually planning on running with this project and seeking funding, and I'm going to shop it at various incubators. I want it to be something I can say with confidence is ready for a production level environment with tens of thousands of simultaneous users. I've got full control of the stack as this is my project. I just don't have a ton of experience with search, so I've gotta do some homework on it.
AbortedWalrusFetus
Member
http://dev.mysql.com/doc/refman/5.6/en/create-table-foreign-keys.html
If you check that out about half way down the page it has an example of how to create foreign keys.
You will be less happy in general with MySQL than PostgreSQL. Most active relational database research happens there first (e.g. serializable snapshot isolation, jsonb indices), its query parser is much more compliant, it has a much stronger track record for reliability, it has a much better query planner, and it improves substantially with every release (full disclosure: I have contributed to the project).
You can get surprisingly far before you really need tens of thousands of simultaneous open database connections (NeoGAF has much fewer than that at any one time) and much further than that before you can't get away with standard read replicas and need a database like Cassandra. If you really want to have high reliability in the face of huge traffic, choosing Cassandra is just the first of many decisions you'll need to make, as it will inform every decision you make with your application. Some examples: how does your application deal with machine death and failover? Load balancing? Will you use an addressing system that abstracts physical addresses? How will you handle DOS attacks? Where and how will you handle consistency vs latency tradeoffs throughout your application? How will you stage release rollouts? If you can't answer those questions, choosing Cassandra may be premature. It's a fantastic database, but it's designed for extreme environments so you really need to make sure you have a usecase for it.
AbortedWalrusFetus
Member
I definitely appreciate where you're coming from. I've got production level experience with all of those things in my professional career. The most honest answer I can give as to why cassandra is because I'm experienced with it and greatly enjoy using it, aside from the practical reasons as to why, which I have plenty of. I've got plenty of experience with SQL Server and MySQL as well, and I just don't think they would fit the environment as ideally as Cassandra does, and in so many ways cassandra is far easier to use.
Two/Three part question for ya', ProGrAF.
Has anyone had any experience with Sams Teach Yourself C++ in 21 Days... from 1999? (Mother bought it because it was cheap >_>)
Second part, does anyone have experience with the Seventh Edition?
Lastly, should I even bother with it, or wait 'til I can scrounge the money together for that C++ Primer Plus book everyone seems to love? Is it a case of "learn right or not at all" or "any learning is better than none." I know that coding is something you likely don't want a fifteen year old book to learn with since it's evolved so much, which is why I ask. Don't want to fill my mind with things that may end up confusing me later on because I learned from an old book.
Has anyone had any experience with Sams Teach Yourself C++ in 21 Days... from 1999? (Mother bought it because it was cheap >_>)
Second part, does anyone have experience with the Seventh Edition?
Lastly, should I even bother with it, or wait 'til I can scrounge the money together for that C++ Primer Plus book everyone seems to love? Is it a case of "learn right or not at all" or "any learning is better than none." I know that coding is something you likely don't want a fifteen year old book to learn with since it's evolved so much, which is why I ask. Don't want to fill my mind with things that may end up confusing me later on because I learned from an old book.
AbortedWalrusFetus
Member
I am actually pretty sure I used that same book... back in like 2000. I was finishing high school and had a few programming courses, liked them, and decided I'd do a program as my graduation project and I did it in C++. I ended up winning the award (and a savings bond!) for the best project in my graduating class for the program. That's about the only thing I remember about the entire book! All I can say is that the fundamentals of C/C++ have not changed overly much since that point in time. I am sure it's far from the best resource available anymore but I am sure there are things of value in there to learn from.
The big question I have for you is, are you doing this to learn programming, or are you doing it to learn C++? If you're doing it to learn Programming I want to encourage you to give Python or another language a shot before C++.
It's not hard to get a working prototype running with solr, it's pretty much pre-configured. There's also a lot of documentation and help available because it's so widespread. Getting it in there early will payoff when you need to refine the search or scale it.
Programming is the intended goal. An interest in computer apps and in-general games for the "for myself" intentions, and an eye on the future with (hopefully) a goodish job for the more important intention.
I went through the first chapter in the book Learning Python the Hard Way about two years ago, but dropped it promptly for my school. Now I'm eighteen and am in that confusing position of what to do for college, job, and future... Or in other words, I'm at home all day while I wait for Spring Semester. I remember back then it was considered one of the best resources out there due to the fact it was 1.) well-written, and 2.) entirely free. Is it still considered one of the better ones out there for someone who has never really gone past a "Hello World!"?
I'd really rather hold off on college for the time being. I want to get a GED, get a job, and help my dad out with all the stress he's carrying. Family of six to care for, he's the only one making an income, and it's shaky, sometimes missing a week at random. They want me to continue an education for the future, but I want to help my dad in the now. So I figured... Math and programming are two things that can be done at home while holding an entry-level job.
Blabbered a bit more than you asked. Sorry. Bullet-point version:
-Looking to program, not so much learn C++
-Used Learning Python the Hard Way in the past, but not past chapter one
-Am interested on the general opinion of the book now, two years later
AbortedWalrusFetus
Member
http://www.codecademy.com/en/tracks/python
Do that. Give it a shot, stick with it for at least a week. It will slowly walk you through not just python, but the fundamentals of computer science. I think by the end of it you'll answer a lot of questions as to whether or not you want to pursue computer science, and if you do you'll have a bit of a head start if you go to college for it or even purchase a book for it.
I recommend python because the syntax is pretty simple, but the language has a lot of depth. It's a language that is rapidly gaining in popularity and you'd be able to find jobs using it. C++ can expose you to a lot of complicated things about programming that while they are important, they can hamper the overall learning process.
Treechopper
Member
Hate to break this to you, but we have another 10,000 posts to go...
I'm wondering if this is an OK place to do it, but here goes. My question concerns assembly language, more specifically, MIPS. So if I wanted to access some memory address, knowing beforehand where exactly we would like to manipulate, how would I do this? It's not a pointer, but just some address where we want to mess around with the value stored there in memory.
Code:
lw $t0-9, memory adress
do stuff on $t0-9
sw $t0-9, memory adressIt has been a few years since I last looked at MIPS assembly, might be that I forgot about the existence of operations on memory besides loading and storing.
I think the thing is the address isn't explicitly stored anywhere in the code. That being said, is addi $t0, $t0, 0xAAAA OK to do?
SailorCosmos
Member
Does anyone have any experience in socket programming in python? I am trying to make an FTP client but am having some issues. The code below lets me communicate with the test FTP server I am using and I am able to send the username, password, and ask for the working directory. However, the connection disconnects immediately after the last line. Does anyone know how I can maintain a connection?
lorebringer
Member
It's not really socket specific, I'm pretty sure it's just that the process is ending and so abandoning the socket. You should just need to add a loop that will request user input until an exit command is given, then close the connection when done. You can handle each individual ftp command based on the user command entered each time.
Vire
Member
Hey GAF,
I've been stuck on this assignment for hours now and I'm looking for any help! Please!
I know this is incorrect because I need Item Prices to be returned as a singular int instead of an array.
The problem is, Java won't let me set an int = to the sum of array. Any help would be super duper appreciated.
I've been stuck on this assignment for hours now and I'm looking for any help! Please!
Code:
// Import Scanner
import java.util.Scanner;
public class Assignment6 {
public static void main(String[] args) {
// Declare variables
Scanner input = new Scanner(System.in);
// An array that stores the first item selection
int[] naItemSelection = new int [13];
int[] naItemPrice = new int[13];
int nIndex = 0;
// An string that stores the users' name
String sName;
// An index to store the first array's values
// Print out question asking for users' name
System.out.print("Please enter your name: ");
// Read in users' name
sName = input.nextLine();
// Print out blank line
System.out.println("");
// Print out menu
System.out.println("BEST PURCHASE PRODUCTS");
System.out.println("1. Smartphone $249");
System.out.println("2. Smartphone case $39");
System.out.println("3. PC Laptop $1149");
System.out.println("4. Tablet $349");
System.out.println("5. Tablet case $49");
System.out.println("6. eReader $119");
System.out.println("7. PC Desktop $899");
System.out.println("8. LED Monitor $299");
System.out.println("9. Laser Printer $399");
System.out.println("10. Complete my order");
// If the total amount of items selection is less than the array length, continue running the loop, if the item selection is 10, end the loop.
for (nIndex=0; (nIndex < naItemSelection.length && naItemSelection[nIndex] !=10); nIndex++){
if(nIndex==0){
System.out.print("Please select an item from the menu above: ");
naItemSelection[nIndex] = input.nextInt();
//If Item Selection in the array is input to 10, break
if(naItemSelection[nIndex]==10){
break;
}//end if
}//end if
else {
System.out.print("Please select another item from the menu above: ");
naItemSelection[nIndex] = input.nextInt();
//If Item Selection in the array is input to 10, break
if(naItemSelection[nIndex]==10){
break;
}//end if
}// end else if
}//end for loop for prompt user
//Call method to calculate item price passing array of item selection
naItemPrice = methodItemPrice(naItemSelection);
//print item price
System.out.println("Item Price: " +
naItemPrice[nIndex]);
}//end main
/**
* Calculates total item price
* @param naNewItemSelection
* @return The calculated item price
*/
public static int [] methodItemPrice(int naNewItemSelection[]){
//Define local variables
int[] naNewItemPrices = new int[13];
int nCount = 0;
for (nCount = 0; nCount < naNewItemSelection.length; nCount++) {
if(naNewItemSelection[nCount] == 1){
naNewItemSelection[nCount] = 249;
}//end if
else if(naNewItemSelection[nCount] == 2){
naNewItemSelection[nCount] = 39;
} // End else if statement
else if(naNewItemSelection[nCount]== 3){
naNewItemSelection[nCount] = 1149;
}
// End if statement
//etc
//Calculate Item Price
naNewItemPrices[nCount] = naNewItemPrices[nCount]+naNewItemSelection[nCount];
} //end for
return naNewItemPrices;
} //end method
}I know this is incorrect because I need Item Prices to be returned as a singular int instead of an array.
The problem is, Java won't let me set an int = to the sum of array. Any help would be super duper appreciated.
If you problem is figuring out how to sum the elements of an array of integers in Java, you will want to use a `for` loop to iterate over the elements of the array, adding each element to a new integer value, 'sum'. Return 'sum' as the result.
Vire
Member
Thanks for the response! Hmm, I thought I already put the calculation in a for loop?
Code:
for (nCount = 0; nCount < naNewItemSelection.length; nCount++) {
if(naNewItemSelection[nCount] == 1){
naNewItemSelection[nCount] = 249;
}//end if
else if(naNewItemSelection[nCount] == 2){
naNewItemSelection[nCount] = 39;
} // End else if statement
else if(naNewItemSelection[nCount]== 3){
naNewItemSelection[nCount] = 1149;
}
//Calculate Item Price
naNewItemPrices[nCount] = naNewItemPrices[nCount]+naNewItemSelection[nCount];
} //end for
return naNewItemPrices;
} //end methodHowever, when I change naNewItemPrices to a regular integer named sum, I get an error stating:
incompatible types: int cannot be converted to int[]
so it looks like this:
Code:
Sum = Sum+naNewItemSelection[nCount]
} //end for
return Sum;
} //end methodPurple Cheeto
Member
Did you change your function signature to match your return type?
i.e. public static int [] functionName() should just be public static int functionName()
Vire
Member
I'm not exactly sure what you mean but I changed this in main so it looks like this:
Code:
FinalSum = methodItemPrice(naItemSelection);
System.out.println("Item Price: " +
FinalSum);
Code:
public static int [] methodItemPrice(int naNewItemSelection[]){However, I get the same error as I was getting down below on the return line.
EDIT: OOOOOH, wow okay. Thank YOU! Such a simple little error driving me nuts. GOT IT!
SailorCosmos
Member
Thanks, added the loop and now I stay connected. Ran into another problem though. I started setting up the user commands. I can send them and the server gets them but say when I send a 'LIST' command the server responds telling me it couldn't establish a data connection. I know I probably have to do a data socket but I haven't a clue how to do it. I send the TYPE and PASV commands to the server and it responds back with the IP address and port but I don't know how to have my client bind to that so that the data connection can be established.
I'm learning Java right now in a computer science class, while loops are confusing me. I have this segment of code, but when I hit run, it skips over the while loop and goes right to the final println statement. I'm doing it like the book showed me, why isn't it working?
Code:
boolean tripOver = false;
while (tripOver = false){
System.out.println("Import the number of miles driven: ");
milesDriven = input.nextInt();
System.out.println("Import the number of gallons used: ");
gallonsUsed = input.nextInt();
System.out.println("-----------------------------------");
System.out.println();
milesPerGallon = milesDriven / gallonsUsed;
System.out.println("Your gas mileage was " + milesPerGallon + " MPG");
totalMPG = totalMPG + milesPerGallon;
System.out.println("Your total MPG was: " + totalMPG);
System.out.println("Are there any more trips? y for Yes and n for No: ");
over = input.next();
if (over == "y")
tripOver = true;
}
System.out.println("You done, son.");Incandenza
Banned
Half and half
Member
^ If it skips over the while loop, I'd say look carefully at that line and compare it to how other while() lines are written.
Edit:
Doh giving mathaou the answer. Shoulda let her/him sweat that out a bit. Those make great lightbulb moments.
Edit:
Doh giving mathaou the answer. Shoulda let her/him sweat that out a bit. Those make great lightbulb moments.
Thanks, man.
Learning any language you're interested in is a good idea. Might want to take a look at Swift too for iOS programming.
AbortedWalrusFetus
Member
I prefer using
while(!tripOver)
Basically "while not tripOver".
When you are using boolean types you don't need to actually have an equality in the condition. The condition evaluates to a boolean anyway. You can just use the boolean itself, or add negation/not (!) to it. It's short hand, more readable, and can prevent that error where you do assignment rather than comparison.
Half and half
Member
I would argue that (!tripOver) is error prone as well since it would be easy to overlook the !. Comparing tripOver to true or false provides additional info about the programmer's intent.
Horses for courses of course
Anyways, does Java not warn about this? My C++ compiler catches these.
This is why Python.
AbortedWalrusFetus
Member
I would argue that (!tripOver) is error prone as well since it would be easy to overlook the !. Comparing tripOver to true or false provides additional info about the programmer's intent.
Horses for courses of course
Anyways, does Java not warn about this? My C++ compiler catches these.
That's why you need well named variables. When it's called "tripOver" you understand the meaning. By inferring what the code is trying to do it highlights the ! for me. But you're right, to each his own.
All modern IDEs give you a warning as far as I remember.
Java doesn't warn you against it except if the variable wasn't initialized.I would argue that (!tripOver) is error prone as well since it would be easy to overlook the !. Comparing tripOver to true or false provides additional info about the programmer's intent.
Horses for courses of course
Anyways, does Java not warn about this? My C++ compiler catches these.
What kind of error are you getting?
I would argue that (!tripOver) is error prone as well since it would be easy to overlook the !. Comparing tripOver to true or false provides additional info about the programmer's intent.
Horses for courses of course
Anyways, does Java not warn about this? My C++ compiler catches these.
You could also switch the logic around. Just call the variable 'notTrippedOver'.
Or (if the condition is slightly less trivial) just extract a method boolean isNotTrippedOver() { return !tripOver; }
Java IDEs may well be able to warn you. E.g. in IntelliJ IDEA there's a very long list of inspection settings where you specify what you'd like to be warned of.
IMO, if you need to write variable == true to make your intent clear, the problem lies with the naming of the variable. Rename the variable to make the condition read like a sentence.
Edit: another way to avoid these kinds of mistakes is to place the constant on the left, since you cannot assign anything to a constant (true == variable).
smokeandmirrors
Banned
I'm feeling kinda motivated to revisit my senior project, clean it up, fix some small bugs,port to iOS, and create an online database for it, but goddamned if I'm not overwhelmed with the garbage I produced in the crunch time before I had to present.
plus it's a decent idea that I would actually use.
actually it may be easier and quicker to rip some of the important classes and restart everything else...
plus it's a decent idea that I would actually use.
actually it may be easier and quicker to rip some of the important classes and restart everything else...
Half and half
Member
I think 'notTripOver' becomes harder to read further down when it's time to break out of the loop: notTripOver = false; <-- I have to think for a second about what that means.
I agree that variable naming is key. I think something like 'while (tripIsInProcess)' reads well since there is not a negatitive comparison. I'd personally still add the == true in there.
Good call on the (true == variable). I see that occasionally in code bases and just chalked it up to personal style. I can see the validity of using that to reduces errors.
Imo one should rarely use negated boolean variable names as it just lowers readability. If you have something like "inProgress" and you always need to use "!inProgress" then maybe "stopped" or something similar would be better than "notInProgress". As "!inProgress" probably reads "not in progress" in any programmers mind who looks at the code anyway.
Also I think == should be reserved when you actually deal with comparisons. Not when dealing with booleans which have their own operators for a reason (that obviously does not apply to languages like C where there's no dedicated boolean type).
Also I think == should be reserved when you actually deal with comparisons. Not when dealing with booleans which have their own operators for a reason (that obviously does not apply to languages like C where there's no dedicated boolean type).
Purple Cheeto
Member
Objective C is kind of a nasty language for a beginner. Swift is probably a bit easier for someone without much programming experience.
close to the edge
Member
Embedded programming is almost exclusively C. C++ is starting to see more use in the last few years I believe and Ada is also used for some application domains (e.g. military airplanes)
According to my Java textbook, this is what Java was originally meant for, as the JVM was supposed to make it easier to program things for a wide variety of architectures, but it never caught on in that domain. Somehow it caught on in other parts of tech.
Code:
openssl::ssl::sslerror: ssl_connect returned=1 errno=0 state=sslv3 read server certificate b: certificate verify failed