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Programming |OT| C is better than C++! No, C++ is better than C

C

close to the edge

Member
tokkun said:
What does the code for the animation constructor and getShape methods look like?
Click to expand...
I just found the error. When I call the constructor like this:
Code: 
sf::CircleShape* circle = new sf::CircleShape(23.0f);
circle->setFillColor(sf::Color::Black);
animation animation(sf::Vector2f(15.f, 15.f), sf::Vector2f(15.f, 150.f), circle, 1.0f);
it works. However, when I try to pass the address of the shape stored in one of my enemy objects (&enemy.getShape() instead of circle as the shape argument) it crashes with that misleading error message. (something about a pure virtual function call) Interestingly, MSVC++ lets you take the address of a temporary object like that and won't even write a warning. clang++ and g++ don't even let you compile it.
 
L

LonelyGreyWolf

Banned
Hey guys. I've just started with programming (python) and I know this is probably a really stupid question, but can anyone help me with this?

a = 95
b = 63
a += b
b += a

What is b? I've tried everything but I keep getting the wrong answer.
 
C

ColtraineGF

Member
LonelyGreyWolf said:
Hey guys. I've just started with programming (python) and I know this is probably a really stupid question, but can anyone help me with this?

a = 95
b = 63
a += b
b += a

What is b? I've tried everything but I keep getting the wrong answer.
Click to expand...
Here's a hint:

x += y

is the same as

x = x + y
 
H

Haly

One day I realized that sadness is just another word for not enough coffee.
a = 95
b = 63
a += b is equivalent to a = 95 + 63 = 158
b += a is equivalent to b = 63 + 158 = 222
 
L

LonelyGreyWolf

Banned
charlemagne said:
Out of interest, what ended up being the aspect that prevented you from figuring it out?
Click to expand...

The tutorial I was reading didn't explain it well. I guess I was thinking too much like math. I wasn't quite sure what "a += b" meant and Google did me no favours. I imagined that a = a and b = b, but if a = a + b then that is of course not the case, unless b = 0. I tried a few different combinations, such as 95 + 63, and then that number + 95 (a + b + a, or 2a + b).

I see now that a = a + b and b = b + a. The number a changes, and I suppose that was the big issue I had.
 
U

usea

Member
LonelyGreyWolf said:
The tutorial I was reading didn't explain it well. I guess I was thinking too much like math. I wasn't quite sure what "a += b" meant and Google did me no favours. I imagined that a = a and b = b, but if a = a + b then that is of course not the case, unless b = 0. I tried a few different combinations, such as 95 + 63, and then that number + 95 (a + b + a, or 2a + b).

I see now that a = a + b and b = b + a. The number a changes, and I suppose that was the big issue I had.
Click to expand...
Ah, yeah. = is the assignment operator/statement. It's not a statement of equality like in math. It changes the value of the variable on the left to be equal to the expression on the right.

For example, if you put this it wouldn't even compile (in most languages). Because you can't change the value of 3 (even to itself).
Code: 
3 = 3

http://en.wikipedia.org/wiki/Assignment_operator#Assignment_versus_equality You're not alone in being confused.
 
I

iapetus

Scary Euro Man
If you want to confuse yourself more, throw in some unary operators. :)

int a = 36;
int b = 17;
a += ++a + b++;
b += a++ + ++b;
 
T

Treechopper

Member
iapetus said:
If you want to confuse yourself more, throw in some unary operators. :)

int a = 36;
int b = 17;
a += ++a + b++;
b += a++ + ++b;
Click to expand...
Thats so evil.

But to add to the discussion it's incredibly useful and helpful. I use them to keep statements more concise, unambiguous and I find it easier to read.
 
L

LonelyGreyWolf

Banned
Can someone give me a hand with using Python. I've downloaded Python and Notepad++. Opening the programs work well. But when I write a code in Notepad++ and save it as a ".py" file it doesn't work to open in Python. Or rather, it seemingly stays open for like a fraction of a second and then shuts itself down.
 
I

injurai

Banned
LonelyGreyWolf said:
Can someone give me a hand with using Python. I've downloaded Python and Notepad++. Opening the programs work well. But when I write a code in Notepad++ and save it as a ".py" file it doesn't work to open in Python. Or rather, it seemingly stays open for like a fraction of a second and then shuts itself down.
Click to expand...

oh, yeah it's just executing to completion then closing before you can really see it's output.

You can enforce a wait for input or something at the end, I don't use python much but I remember running into this.
 
Zoe

Zoe

Member
injurai said:
at the end

a == 91
b == 127
Click to expand...

I got 90 and 125. (edit: whoops, forgot a increments in the second statement, and I was working off the original value of b in the second)

I'm a little uncertain on whether += always uses the original value, but don't forget that post++ and pre++ are different.
 
T

Tamanon

Banned
LonelyGreyWolf said:
Can someone give me a hand with using Python. I've downloaded Python and Notepad++. Opening the programs work well. But when I write a code in Notepad++ and save it as a ".py" file it doesn't work to open in Python. Or rather, it seemingly stays open for like a fraction of a second and then shuts itself down.
Click to expand...

It's working, the console just closes.

Add this line at the end of your programs for now:
Code: 
raw_input()

This will leave the console open to view your stuff until you hit enter.

Alternatively, do your start in IDLE, the built-in Python editor. That way when you run from there, it opens in a console shell that stays open.
 
H

Haly

One day I realized that sadness is just another word for not enough coffee.
iapetus said:
If you want to confuse yourself more, throw in some unary operators. :)

int a = 36;
int b = 17;
a += ++a + b++;
b += a++ + ++b;
Click to expand...

a == 36
b == 17

a += (++a) + (b++)
==
a = a + (++a) + (b++)
==
a = 36 + 37 + 17, a == 90, b == 18

b += (a++) + (++b)
==
b = b + (a++) + (++b)
==
b = 18 + 90 + 19, b == 127, a == 91

Is this right?
 
I

injurai

Banned
Zoe said:
I got 90 and 125. (edit: whoops, 91, forgot a increments in the second statement)

I'm a little uncertain on whether += always uses the original value, but don't forget that post++ and pre++ are different.
Click to expand...

don't forget?

I think you forgot!!!

Haly said:
a == 36
b == 17

a += (++a)+ (b++)
==
a = a + (++a) + (b++)
==
a = 36 + 37 + 17, a == 90, b == 18

b += (a++) + (++b)
==
b = b + (a++) + (++b)
==
b = 18 + 90 + 19, b == 127, a == 91

Is this right?
Click to expand...

Yeah, that's what I did.
 
H

Haly

One day I realized that sadness is just another word for not enough coffee.
Also this should be established as a war crime.
 
C

close to the edge

Member
Haly said:
a == 36
b == 17

a += (++a) + (b++)
==
a = a + (++a) + (b++)
==
a = 36 + 37 + 17, a == 90, b == 18

b += (a++) + (++b)
==
b = b + (a++) + (++b)
==
b = 18 + 90 + 19, b == 127, a == 91

Is this right?
Click to expand...

I was curious, so I compiled it in Visual Studio:
Code: 
#include "stdafx.h"
#include <iostream>

using std::cout; using std::endl;

int main(int argc, char **argv)
{
	int a = 36;
	int b = 17;
	a += ++a + b++;
	b += a++ + ++b;
	cout << "a = " << a << endl;
	cout << "b = " << b << endl;
	getchar();
	return 0;
}
Output is
Code: 
a = 92
b = 129

Don't ask me how this comes to be, your solution seems pretty intuitive to me.
 
H

Haly

One day I realized that sadness is just another word for not enough coffee.
Well now my programming confidence is totally shattered.
 
L

Leezard

Member
Haly said:
a == 36
b == 17

a += (++a) + (b++)
==
a = a + (++a) + (b++)
==
a = 36 + 37 + 17, a == 90, b == 18

b += (a++) + (++b)
==
b = b + (a++) + (++b)
==
b = 18 + 90 + 19, b == 127, a == 91

Is this right?
Click to expand...
The first one should be a=37+37+17==91,b==18.
Second should be b=19+91+19==129,a==92.
 
H

Haly

One day I realized that sadness is just another word for not enough coffee.
Leezard said:
The first one should be a=37+37+17==91,b==18.
Second should be b=19+91+19==129,a==92.
Click to expand...

So you're saying

a += (++a) + (b++)

...actually expands to...

a = (++a) + (b++) + a?

That's the only way I can imagine it working out to 92.
 
L

Leezard

Member
Haly said:
So you're saying

a += (++a) + (b++)

...actually expands to...

a = (++a) + (b++) + a?

That's the only way I can imagine it working out to 92.
Click to expand...
It does not matter if you type a + ++a or ++a + a, the ++ increases a by one before the statement is evaluated.
Edit: The statement
a = a + (b++) + ++a
Is equal to
++a;
a = a + (b++) + a;
 
H

Haly

One day I realized that sadness is just another word for not enough coffee.
Okay, I see. So pre-increment is evaluated before any unary operation in a statement.
 
L

LonelyGreyWolf

Banned
injurai said:
oh, yeah it's just executing to completion then closing before you can really see it's output.

You can enforce a wait for input or something at the end, I don't use python much but I remember running into this.
Click to expand...

Tamanon said:
It's working, the console just closes.

Add this line at the end of your programs for now:
Code: 
raw_input()

This will leave the console open to view your stuff until you hit enter.

Alternatively, do your start in IDLE, the built-in Python editor. That way when you run from there, it opens in a console shell that stays open.
Click to expand...

Thanks. I tried adding that line to the end but it changed nothing. Using IDLE worked great though.
 
I

injurai

Banned
Haly said:
Well now my programming confidence is totally shattered.
Click to expand...

Leezard said:
It does not matter if you type a + ++a or ++a + a, the ++ increases a by one before the statement is evaluated.
Edit: The statement
a = a + (b++) + ++a
Is equal to
++a;
a = a + (b++) + a;
Click to expand...

Haly said:
Okay, I see. So pre-increment is evaluated before any unary operation in a statement.
Click to expand...

the nuances of programming amaze me, thanks for the moment of clarity
 
A

AbortedWalrusFetus

Member
I'm running a MERGE to update/insert data into a table as it comes in. I'm not sure how I can prevent this deadlock from occurring or minimize it's occurrence.

Code: 
<deadlock-list>
 <deadlock victim="process176af4988">
  <process-list>
   <process id="process176af4988" taskpriority="0" logused="1028" waitresource="KEY: 9:72057594041663488 (266fc93ba77f)" waittime="414" ownerId="20808905" transactionname="implicit_transaction" lasttranstarted="2013-07-18T14:42:31.483" XDES="0x19115b950" lockMode="U" schedulerid="4" kpid="8736" status="suspended" spid="134" sbid="0" ecid="0" priority="0" trancount="2" lastbatchstarted="2013-07-18T14:42:31.483" lastbatchcompleted="2013-07-18T14:42:31.480" clientapp="jTDS" hostname="CLDEV4" hostpid="123" loginname="PANS_USER" isolationlevel="read committed (2)" xactid="20808905" currentdb="9" lockTimeout="4294967295" clientoption1="671088672" clientoption2="128058">
    <executionStack>
     <frame procname="CATE.dbo.pr_mergeCurrentPosition" line="24" stmtstart="1116" sqlhandle="0x03000900fd706e5bbc5df000ffa100000100000000000000">
MERGE
	CATE.dbo.CURRENT_POSITION_AIS WITH (UPDLOCK) AS cpa
USING (
	VALUES(@mmsiNbr)
) AS cpatemp (mmsi_nbr)
ON cpa.mmsi_nbr = cpatemp.mmsi_nbr
WHEN MATCHED THEN 
	UPDATE SET nav_status = @navStatus, rot = @rot, sog = @sog, pos_accuracy = @posAccuracy, lat = @lat,
	lon = @lon, cog = @cog, true_heading = @trueHeading, time_stamp_sec = @timeStampSec, special_maneuver_ind = @specialManeuverInd,
	raim_flag = @raimFlag, comm_state = @commState, updt_dt = @updtDt, position = @position,
	imo_nbr = @imoNbr, call_sign = @callSign, vessel_name = @vesselName
WHEN NOT MATCHED THEN	
	INSERT (mmsi_nbr,nav_status,rot,sog,pos_accuracy,lat,lon,cog,true_heading,time_stamp_sec,special_maneuver_ind,raim_flag,comm_state,updt_dt,position,
	imo_nbr, call_sign, vessel_name)
	VALUES(@mmsiNbr,@navStatus,@rot,@sog,@posAccuracy,@lat,@lon,@cog,@trueHeading,@timeStampSec,@specialManeuverInd,@raimFlag,@commState,@updtDt,@position,
	@imoNbr, @callSign, @vesselName)
;     </frame>
    </executionStack>
    <inputbuf>
Proc [Database Id = 9 Object Id = 1533964541]    </inputbuf>
   </process>
   <process id="process52dddc8" taskpriority="0" logused="29980" waitresource="KEY: 9:72057594041663488 (a8535ed1a10a)" waittime="387" ownerId="20808883" transactionname="implicit_transaction" lasttranstarted="2013-07-18T14:42:31.470" XDES="0x96688e80" lockMode="U" schedulerid="8" kpid="5256" status="suspended" spid="133" sbid="0" ecid="0" priority="0" trancount="2" lastbatchstarted="2013-07-18T14:42:31.470" lastbatchcompleted="2013-07-18T14:42:31.460" clientapp="jTDS" hostname="CLDEV4" hostpid="123" loginname="PANS_USER" isolationlevel="read committed (2)" xactid="20808883" currentdb="9" lockTimeout="4294967295" clientoption1="671088672" clientoption2="128058">
    <executionStack>
     <frame procname="CATE.dbo.pr_mergeCurrentPosition" line="24" stmtstart="1116" sqlhandle="0x03000900fd706e5bbc5df000ffa100000100000000000000">
MERGE
	CATE.dbo.CURRENT_POSITION_AIS WITH (UPDLOCK) AS cpa
USING (
	VALUES(@mmsiNbr)
) AS cpatemp (mmsi_nbr)
ON cpa.mmsi_nbr = cpatemp.mmsi_nbr
WHEN MATCHED THEN 
	UPDATE SET nav_status = @navStatus, rot = @rot, sog = @sog, pos_accuracy = @posAccuracy, lat = @lat,
	lon = @lon, cog = @cog, true_heading = @trueHeading, time_stamp_sec = @timeStampSec, special_maneuver_ind = @specialManeuverInd,
	raim_flag = @raimFlag, comm_state = @commState, updt_dt = @updtDt, position = @position,
	imo_nbr = @imoNbr, call_sign = @callSign, vessel_name = @vesselName
WHEN NOT MATCHED THEN	
	INSERT (mmsi_nbr,nav_status,rot,sog,pos_accuracy,lat,lon,cog,true_heading,time_stamp_sec,special_maneuver_ind,raim_flag,comm_state,updt_dt,position,
	imo_nbr, call_sign, vessel_name)
	VALUES(@mmsiNbr,@navStatus,@rot,@sog,@posAccuracy,@lat,@lon,@cog,@trueHeading,@timeStampSec,@specialManeuverInd,@raimFlag,@commState,@updtDt,@position,
	@imoNbr, @callSign, @vesselName)
;     </frame>
    </executionStack>
    <inputbuf>
Proc [Database Id = 9 Object Id = 1533964541]    </inputbuf>
   </process>
  </process-list>
  <resource-list>
   <keylock hobtid="72057594041663488" dbid="9" objectname="CATE.dbo.CURRENT_POSITION_AIS" indexname="CURRENT_POSITION_AIS_PK" id="locke97e7a80" mode="X" associatedObjectId="72057594041663488">
    <owner-list>
     <owner id="process52dddc8" mode="X"/>
    </owner-list>
    <waiter-list>
     <waiter id="process176af4988" mode="U" requestType="wait"/>
    </waiter-list>
   </keylock>
   <keylock hobtid="72057594041663488" dbid="9" objectname="CATE.dbo.CURRENT_POSITION_AIS" indexname="CURRENT_POSITION_AIS_PK" id="lock101f14a00" mode="X" associatedObjectId="72057594041663488">
    <owner-list>
     <owner id="process176af4988" mode="X"/>
    </owner-list>
    <waiter-list>
     <waiter id="process52dddc8" mode="U" requestType="wait"/>
    </waiter-list>
   </keylock>
  </resource-list>
 </deadlock>
</deadlock-list>
 
A

AbortedWalrusFetus

Member
usea said:
I've never used MERGE, but funny coincidence: we have a big project with AIS data, too.
Click to expand...

Have fun with it. The parsing and storing of the data is just sort of ridiculous. If you have a global feed it's just so much data that it's hard to deal with. If you're getting it in raw NMEA format parsing it can be tough, and from my experience the open source parsers are pretty slow.

I was hoping to be able to concurrently update/insert AIS positions to the database, but whenever 2 transactions happen at once I get deadlocks galore. I'm not sure what I am doing wrong. I don't even know if JDBC supports snapshot isolation levels either. I basically have 1000 of those store proc calls in a single batch transaction. I was hoping to be able to execute multiple transactions at once to reduce the overhead from I/O across the network. I've basically just had to increase the batch size so that no actual concurrency occurs because of the frequency of the deadlocks.
 
I

injurai

Banned
Notrollious said:
Yeah I put values into my code and it worked but stupidly forgot to add them to the post :\
Click to expand...
I only worked it by hand but
to me I read this as being 3 possible things

c += a++ + b++ + d -> 6 + 2 + 4 + 3 == 15
c += a++ + b + ++d -> 6 + 2 + 4 + 4 == 16
c += a + ++b + ++d -> 6 + 2 + 5 + 4 == 17

so iunno...
 
W

Water

Member
Notrollious said:
I tried running c += a+++b+++++d but it barfed on me
Click to expand...
That doesn't work, because what comes after b gets parsed as ++ ++. Later in the compilation that turns out to have invalid semantics. The compiler doesn't go back to the parsing phase at that point and go, "hey, could there have been some other way to parse that"?

The reason b ++ ++ is broken is that the result of b++ is a temporary value you can't assign into, but the second ++ tries to assign into it.
 
U

usea

Member
AbortedWalrusFetus said:
Have fun with it. The parsing and storing of the data is just sort of ridiculous. If you have a global feed it's just so much data that it's hard to deal with. If you're getting it in raw NMEA format parsing it can be tough, and from my experience the open source parsers are pretty slow.

I was hoping to be able to concurrently update/insert AIS positions to the database, but whenever 2 transactions happen at once I get deadlocks galore. I'm not sure what I am doing wrong. I don't even know if JDBC supports snapshot isolation levels either. I basically have 1000 of those store proc calls in a single batch transaction. I was hoping to be able to execute multiple transactions at once to reduce the overhead from I/O across the network. I've basically just had to increase the batch size so that no actual concurrency occurs because of the frequency of the deadlocks.
Click to expand...
Our project is in maintenance mode, having been cobbled together haphazardly before I joined the company. Ours isn't a global feed; just a single stretch of the Mississippi river. And it's still a ton of data, so I can only imagine the quantity you're looking at.
 
A

AbortedWalrusFetus

Member
usea said:
Our project is in maintenance mode, having been cobbled together haphazardly before I joined the company. Ours isn't a global feed; just a single stretch of the Mississippi river. And it's still a ton of data, so I can only imagine the quantity you're looking at.
Click to expand...

Couple that with the fact that I am solo on this project module : )
 
M

Mister Zimbu

Member
Rant time again. I'll keep it short.

Jira is awful.
Greenhopper is awful.
Bonfire is awful.

All three of them together is an abomination unto mankind.
 
U

usea

Member
Greenhopper looks like Trello. Is that basically what it is? I like trello a lot for personal use.

As for Atlassian products, we use Crucible/Fisheye and Bamboo at work. They get the job done, but the UIs are terrible. Still better than not having them.

I've never used Jira. We use Fogbugz and Kiln.
 
M

Mister Zimbu

Member
Jira's okay as a bug tracker once you get used to the complete clusterfuck of an interface. There's some capabilities I'd like to have that don't exist (create filters based on project categories, be able to add a filter to all users instead of just me, etc.), but overall it does its job acceptably. I can't comprehend how one could actually use JIRA alone for projects that aren't in the "maintenance stage", the interface seems to be just too archaic for that.

I only mentioned Bonfire because it was the latest thing that was frustrating me.

Basically we have a Scrum project in Greenhopper. I deployed a release candidate of the latest version of our software to a server and want to begin testing. I want to be able to rapidly put bugs into the system and assign them automatically to the current sprint. You can *technically* do this, but the interface for doing so is clunky at best.

We don't actually use Scrum as a development methodology (really closer to waterfall than anything else). Greenhopper used to be perfect - you could assign tasks to versions as you see fit, while you were creating them, and move things between versions as well. They stopped supporting the interface that worked, and forced you into Scrum or Kanban (which seems to be even more useless).
 
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