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Thread Rules
1. This is not a "do my homework for me" thread. If you have specific questions, ask, but don't post an assignment or homework problem and expect an exact solution.
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United States958 Posts
On September 03 2015 20:42 Manit0u wrote:I'm no good with trigonometry. Could you help me out with Haversine formula a bit? I have this query to get locations in select radius range from target location. Could it be made simpler? It works but it looks horrible...
$query = $queryBuilder
->select('CAST((2 * ATAN2(SQRT(POW(SIN(RADIANS(latitude - '
.$latitude
.') / 2) , 2) + POW(SIN(RADIANS(longitude - '
.$longitude
.') / 2) , 2) * COS(RADIANS('
.$latitude
.')) * COS(RADIANS(latitude))), SQRT(1 - POW(SIN(RADIANS(latitude - '
.$latitude
.') / 2) , 2) + POW(SIN(RADIANS(longitude - '
.$longitude
.') / 2) , 2) * COS(RADIANS('
.$latitude
.')) * COS(RADIANS(latitude)))) * 6371) AS DECIMAL(65,10)) AS d')
->having($expr->lte('d', ':radius'))
->setParameter('radius', $radius)
->getQuery();
You consider using MySQL gis functions? I've never personally used it by they're meant for this stuff and if you using not ancient MySQL you aren't even stuck with myisam to use.
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This may be more a GIS question, but I have a set of lat/long coordinates, and I want to find something like a mean point from these. So my plan is to get Cartesian Coordinates from the lat/long pairs, and then I think I'll just need to sum them all and normalize the vector.
Anywho, I can't even get a lat/lon pair to convert to a vector and back. Any help/advice would be awesome.
Here's my code:
<code>def convert_to_dec_degrees(deg, minutes, sec, direction):
dec = deg + minutes/60 + sec/3600
if direction == 'S' or direction == 'W':
dec *= -1
return dec
def convert_to_vector(r, lat, long):
lat = 90 - lat
x = r*math.sin(lat)*math.cos(long)
y = r*math.sin(lat)*math.sin(long)
z = r*math.cos(lat)
return x, y, z
def convert_to_lat_long(x, y, z):
r = math.sqrt(math.pow(x, 2)+math.pow(y, 2)+math.pow(z, 2))
lat = math.acos(z/r)*180/math.pi
long = math.atan2(x, y)*180/math.pi
return lat, long</code>
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Wow
So I've been using Java for a web application and I've still been learning, but I just found out that EL in jsp will automatically convert your class statements so if you want to use a class function such as user.getName() you'd have to type it out as user.name and you can't call the function directly. Confusing as hell
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For some reason that sounds really normal, which feels weird to say...
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On September 06 2015 16:01 Itsmedudeman wrote:
Wow
So I've been using Java for a web application and I've still been learning, but I just found out that EL in jsp will automatically convert your class statements so if you want to use a class function such as user.getName() you'd have to type it out as user.name and you can't call the function directly. Confusing as hell
I kind of like that. You type it as you'd like to access a property and it automatically looks for a getter for it.
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On September 06 2015 16:01 Itsmedudeman wrote:
Wow
So I've been using Java for a web application and I've still been learning, but I just found out that EL in jsp will automatically convert your class statements so if you want to use a class function such as user.getName() you'd have to type it out as user.name and you can't call the function directly. Confusing as hell
I remember being confused about this same thing a few years ago too.
Gotten used to it by now though.
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Hey Guys. I have a newbie question.
I just downloaded Eclipse Mars for C++ coding (windows 64 bit computer for me)
Whenever I run the simplest of code, I get the following message: Launch failed. Binary not found.
Any help?
EDIT: Saw some online threads already, didn't help much :/
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On September 09 2015 11:14 Housemd wrote:
Hey Guys. I have a newbie question.
I just downloaded Eclipse Mars for C++ coding (windows 64 bit computer for me)
Whenever I run the simplest of code, I get the following message: Launch failed. Binary not found.
Any help?
EDIT: Saw some online threads already, didn't help much :/
You might need to set the working directory of the project (to the directory that the executable is built to).
Alternatively, you might need to set the startup project, if you have an example with lots of projects.
(Source: I have never used Eclipse)
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On September 09 2015 11:40 meatpudding wrote:Show nested quote +On September 09 2015 11:14 Housemd wrote:
Hey Guys. I have a newbie question.
I just downloaded Eclipse Mars for C++ coding (windows 64 bit computer for me)
Whenever I run the simplest of code, I get the following message: Launch failed. Binary not found.
Any help?
EDIT: Saw some online threads already, didn't help much :/ You might need to set the working directory of the project (to the directory that the executable is built to). Alternatively, you might need to set the startup project, if you have an example with lots of projects. (Source: I have never used Eclipse)
Yea, unfortunately I'm such a newb that without a step by step procedure or something of that like, I will most likely mess my computer up 
If anyone could do that, it would be great. If not, I'll ask my professor tomorrow.
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So I'm trying to learn how to code properly and I was wondering if I have a function that wants to update or retrieve an entity based on name should I connect and close connections to the database within that function? Or should I make it simpler and just update the object itself and rely on the user to open and close connections while passing the proper parameters to the function? I'd imagine that opening and closing connections could be pretty repetitive and inefficient after awhile. For example in my application I want to check to see if a value exists and then add the object if it doesn't. With 2 separate functions for checking existence and adding this would require 2 separate connections to the database.
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On September 10 2015 14:19 Itsmedudeman wrote:
So I'm trying to learn how to code properly and I was wondering if I have a function that wants to update or retrieve an entity based on name should I connect and close connections to the database within that function? Or should I make it simpler and just update the object itself and rely on the user to open and close connections while passing the proper parameters to the function? I'd imagine that opening and closing connections could be pretty repetitive and inefficient after awhile. For example in my application I want to check to see if a value exists and then add the object if it doesn't. With 2 separate functions for checking existence and adding this would require 2 separate connections to the database.
A function should do 1 thing and 1 thing only, it cocern should not be checking for connections, it should be given a proper connection or something else that handles all of that. so that the function only has the be concernd with creating the correct query.
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Hey guys, another stupid simple question that I can't seem to figure out.
int a = 10;
int b = 5;
int c = a+b:
if (a+b) = 189
{
cout << "I'm the best"<<end1;
}
else
{
cout << "I suck at programming"<<end1;
}
so basically, i don't get one thing. obviously a+b doesn't equal 189 but i keep getting only the former boolean condition. Meaning it keeps printing "I'm the best." Can someone guide me through this issue?
EDIT: This is c++. Just using an online compiler.
EDIT: NVM I'm stupid. supposed to be if (a+b) == 189.
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You should really fix this code...
if (c == 189) { //note the parentheses around expression
//code
}
On another note, a nice piece of reading I've found:
NoSQL is Hard
So should Stack Overflow have scaled out instead of up, just in case?
What some don't realize is NoSQL is hard. Relational databases have many many faults, but they make a lot of common tasks simple while hiding both the cost and complexity. If you want to know how many black Prius cars are in inventory, for example, then that's pretty easy to do.
Not so with most NoSQL databases (I'll speak generally here, some NoSQL databases have more features than others). You would have program a counter of black Prius cars yourself, up front, in code. There are no aggregate operators. You must maintain secondary indexes. There's no searching. There are no distributed queries across partitions. There's no Group By or Order By. There are no cursors for easy paging through result sets. Returning even 100 large records at time may timeout. There may be quotas that are very restrictive because they must limit the amount of IO for any one operation. Query languages may lack expressive power.
The biggest problem of all is that transactions can not span arbitrary boundaries. There are no ACID guarantees beyond a single record or small entity group. Once you wrap your head around what this means for the programmer it's not a pleasant prospect at all. References must be manually maintained. Relationships must be manually maintained. There are no cascading deletes that act correctly during a failure. Every copy of denormalized data must be manually tracked and updated taking into account the possibility of partial failures and externally visible inconsistency.
All this functionality must be written manually by you in your code. While flexibility to write your own code is great in an OLAP/map-reduce situation, declarative approaches still cover a lot of ground and make for much less brittle code.
What you gain is the ability to write huge quantities of data. What you lose is complacency. The programmer must be very aware at all times that they are dealing with a system where it costs a lot to perform distribute operations and failure can occur at anytime.
All this may be the price of building a truly scalable and distributed system, but is this really the price you want to pay?
Source: http://highscalability.com/stack-overflow-architecture
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On September 11 2015 11:50 Housemd wrote:
Hey guys, another stupid simple question that I can't seem to figure out.
int a = 10;
int b = 5;
int c = a+b:
if (a+b) = 189
{
cout << "I'm the best"<<end1;
}
else
{
cout << "I suck at programming"<<end1;
}
so basically, i don't get one thing. obviously a+b doesn't equal 189 but i keep getting only the former boolean condition. Meaning it keeps printing "I'm the best." Can someone guide me through this issue?
EDIT: This is c++. Just using an online compiler.
EDIT: NVM I'm stupid. supposed to be if (a+b) == 189.
I amactually quite surprised that that doesn't just give a syntax error. What compiler are you using?
manit0u corrected your code, but the problem is basically this:
if (a+b)=189
This has two major problems: the first is that = is an assignment operator in C++, so your code there is trying to assign 189 to (a+b), which is jibberish and should give a syntax error all on its own.
Your second problem is that the condition of an if statement should be surrounded by parentheses in C++. Now it has been a while since I did much in C++, so it interprets (a+b) as the condition, and then the parser should, once again give a syntax error, because what follows is jibberish.
So... your online compiler seems pretty bad. Please download an ANSI C++ compiler, because what you have, definitely isn't.
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lol I thought he was coding in another language because there's no way that could compile...
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On September 14 2015 05:03 Blisse wrote:
lol I thought he was coding in another language because there's no way that could compile...
Apart from assignment/expression problem, there's also "end1" instead of "endl" 
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EPT
