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digitalmars.D - help: strange problem with D

reply clayasaurus <clayasaurus gmail.com> writes:
Hello, I'm having a strange problem with D and hope someone out there 
smarter than me can help :)

I have this class that holds a struct array of data. I save it to a 
file, and then I load it, but before loading it, I set the data's length 
to zero like so...

data.length = 0; // is this the same as removing all data from data?

load(data); // loads the data, inside the function it tells me that data 
is a certain length, like say 4

writefln(data.length); // now it tells me data.length is 8. wtf?

I'm wondering, is there something besides data.length = 0; to ensure all 
data is removed from data?

This problem confuses me as it doesn't make any sense :(
Sep 11 2004
parent reply Nick <Nick_member pathlink.com> writes:
It's hard to understand exactly what you are doing unless you post some of your
code. If you do that we will try to help you.

Nick

In article <chv6v0$2uet$1 digitaldaemon.com>, clayasaurus says...

Hello, I'm having a strange problem with D and hope someone out there 
smarter than me can help :)

I have this class that holds a struct array of data. I save it to a 
file, and then I load it, but before loading it, I set the data's length 
to zero like so...

data.length = 0; // is this the same as removing all data from data?

load(data); // loads the data, inside the function it tells me that data 
is a certain length, like say 4

writefln(data.length); // now it tells me data.length is 8. wtf?

I'm wondering, is there something besides data.length = 0; to ensure all 
data is removed from data?

This problem confuses me as it doesn't make any sense :(
Sep 11 2004
parent reply clayasaurus <clayasaurus gmail.com> writes:
Nick wrote:

 It's hard to understand exactly what you are doing unless you post some of your
 code. If you do that we will try to help you.
 
 Nick


Here's some code. I could post more if that would be more helpful.

// EDITOR.d code (main program) /////////////////////////////////////
textureManager.textures.length = 0;
// load it up				
load(fileOpen.filename); // inside here it tells me textures length is 'x'
				
int length = textureManager.textures.length; // here it tells me 
textures length is 'x * 2'

// LOAD code ////////////////////////////////////////////
void load(char[] argFileName) // serialization works 8-18-04
{// NOTE: Files must be saved and loaded in the same order
   debug logf("engine: getting ready to load ", argFileName);
			
   File file = new File(argFileName, FileMode.In);

   debug logf("engine: ", argFileName, " opened for reading");
			
   rectangleManager.read(file);
   player.read(file);
   textureManager.read(file);
		
   int len = textureManager.textures.length; // dunno why this is needed 
*confused*, but if I don't, it continues forever
   for (int i = 0; i < len; i++)
   {
 
textureManager.add(textureManager.textures[i].name,textureManager.textures[i].colormode);
   }

   file.close();
   delete file;
		
   debug logf("engine: ", argFileName, "closed. loading done.");
   debug writefln("engine: ", argFileName, " loaded.");
}
Sep 11 2004
parent reply Nick <Nick_member pathlink.com> writes:
In article <chvbr9$30oe$1 digitaldaemon.com>, clayasaurus says...


   textureManager.read(file);


What does this do? Does it set textureManager.textures.length?


		
   int len = textureManager.textures.length; // dunno why this is needed 
*confused*, but if I don't, it continues forever
   for (int i = 0; i < len; i++)
   {
 
textureManager.add(textureManager.textures[i].name,textureManager.textures[i].colormode);
   }


What does this do? I'm just guessing, but does textureManager.add() add the
textures to the end of textureManager.textures? If so, they you are simply
adding the textures in textureManager.textures into textureManager.textures
again, thereby doubling it's size. Since textureManager.textures.length keeps
getting bigger each time you add() a texture, your loop never stops (until it
runs out of memory.) Does this make any sense?

Nick
Sep 11 2004
next sibling parent reply clayasaurus <clayasaurus gmail.com> writes:
Nick wrote:

 In article <chvbr9$30oe$1 digitaldaemon.com>, clayasaurus says...
 What does this do? I'm just guessing, but does textureManager.add() add the
 textures to the end of textureManager.textures? If so, they you are simply
 adding the textures in textureManager.textures into textureManager.textures
 again, thereby doubling it's size. Since textureManager.textures.length keeps
 getting bigger each time you add() a texture, your loop never stops (until it
 runs out of memory.) Does this make any sense?
 
 Nick
 


Ah! Thank you! Yes that is exactly what is happening, I was trying to 
use add to generate the textures, but forget it adds one to the length 
*oops*

Well I got it fixed now. Thanks alot.
Sep 11 2004
next sibling parent Nick <Nick_member pathlink.com> writes:
In article <chvfet$nq$1 digitaldaemon.com>, clayasaurus says...

Nick wrote:

 In article <chvbr9$30oe$1 digitaldaemon.com>, clayasaurus says...
 What does this do? I'm just guessing, but does textureManager.add() add the
 textures to the end of textureManager.textures? If so, they you are simply
 adding the textures in textureManager.textures into textureManager.textures
 again, thereby doubling it's size. Since textureManager.textures.length keeps
 getting bigger each time you add() a texture, your loop never stops (until it
 runs out of memory.) Does this make any sense?
 
 Nick
 


Ah! Thank you! Yes that is exactly what is happening, I was trying to 
use add to generate the textures, but forget it adds one to the length 
*oops*

Well I got it fixed now. Thanks alot.
Sep 13 2004
prev sibling parent Nick <Nick_member pathlink.com> writes:
In article <chvfet$nq$1 digitaldaemon.com>, clayasaurus says...

Ah! Thank you! Yes that is exactly what is happening, I was trying to 
use add to generate the textures, but forget it adds one to the length 
*oops*

Well I got it fixed now. Thanks alot.


No problem :-)

(Ignore the double post, misplaced a mouse click)

Nick
Sep 13 2004
prev sibling parent reply Sha Chancellor <schancel pacific.net> writes:
In article <chve8j$31jk$1 digitaldaemon.com>,
 Nick <Nick_member pathlink.com> wrote:


 In article <chvbr9$30oe$1 digitaldaemon.com>, clayasaurus says...
 

   textureManager.read(file);


 
 What does this do? Does it set textureManager.textures.length?
 

		
   int len = textureManager.textures.length; // dunno why this is needed 
*confused*, but if I don't, it continues forever
   for (int i = 0; i < len; i++)
   {
 
textureManager.add(textureManager.textures[i].name,textureManager.textures[i]
.colormode);
   }


 
 What does this do? I'm just guessing, but does textureManager.add() add the
 textures to the end of textureManager.textures? If so, they you are simply
 adding the textures in textureManager.textures into textureManager.textures
 again, thereby doubling it's size. Since textureManager.textures.length keeps
 getting bigger each time you add() a texture, your loop never stops (until it
 runs out of memory.) Does this make any sense?
 
 Nick


Why don't you use a foreach?
Sep 12 2004
parent reply clayasaurus <clayasaurus gmail.com> writes:
Sha Chancellor wrote:

 Why don't you use a foreach?


What distinct advantages does foreach have over for loops? Is it just 
syntatical sugar?

Also, in for loops it's easy to see what number (index) i'm on.

I looked at the dsource.org foreach tutorials and it seems you have to 
overload the opApply operator for classes?

I dunno the for loop just seems simpler and less confusing to me, and I 
don't see any clear advantages with using foreach. *enlighten me*
Sep 12 2004
next sibling parent reply Andy Friesen <andy ikagames.com> writes:
clayasaurus wrote:

 Sha Chancellor wrote:
 

 Why don't you use a foreach?


 
 
 What distinct advantages does foreach have over for loops? Is it just 
 syntatical sugar?
 
 Also, in for loops it's easy to see what number (index) i'm on.
 
 I looked at the dsource.org foreach tutorials and it seems you have to 
 overload the opApply operator for classes?
 
 I dunno the for loop just seems simpler and less confusing to me, and I 
 don't see any clear advantages with using foreach. *enlighten me*


opApply and foreach provide a means to abstract out the mechanism for 
iteration in a clean way, which makes for code that describes itself better:

     LinkedList!(int) list;
     int[] array;

     foreach (int i; list) { ... }
     foreach (int i; array) { ... }

The details of how the iteration is implemented aren't usually important 
to the actual algorithm, so it makes sense that they be omitted.

If memory serves, you can get the numeric index too:

     foreach (int index, int element; array) { ... }

  -- andy
Sep 12 2004
parent Tyro <ridimz_at yahoo.dot.com> writes:
Andy Friesen wrote:


 clayasaurus wrote:
 

 Sha Chancellor wrote:


 Why don't you use a foreach?




 What distinct advantages does foreach have over for loops? Is it just 
 syntatical sugar?

 Also, in for loops it's easy to see what number (index) i'm on.

 I looked at the dsource.org foreach tutorials and it seems you have to 
 overload the opApply operator for classes?

 I dunno the for loop just seems simpler and less confusing to me, and 
 I don't see any clear advantages with using foreach. *enlighten me*


 
 
 opApply and foreach provide a means to abstract out the mechanism for 
 iteration in a clean way, which makes for code that describes itself 
 better:
 
     LinkedList!(int) list;
     int[] array;
 
     foreach (int i; list) { ... }
     foreach (int i; array) { ... }
 
 The details of how the iteration is implemented aren't usually important 
 to the actual algorithm, so it makes sense that they be omitted.
 
 If memory serves, you can get the numeric index too:
 
     foreach (int index, int element; array) { ... }
 
  -- andy


Memory does serve you correctly Andy, as a matter of fact I use this 
every time I need an iterator. Being a tyro and all, I am prone to 
mistakes and foreach helps me completely eliminate on of the most 
annoying of them (the "off-by-one" error). Not only that, it is far more 
intuitive than it's predecessor.

If I had my way, "for" loops would be removed from the language. And in 
order to make in more powerful, I'd change the foreach such things as:

   foreach(int i || double d; container) { ... }
   foreach(char c && int i; container) { ... }

in addition to its current functionality. Note: container refers to 
aggregate data types such as lists, arrays, structs, classes, and any 
variation thereof.

Andrew
Sep 12 2004
prev sibling parent reply Nick <Nick_member pathlink.com> writes:
In article <ci2en1$avj$1 digitaldaemon.com>, clayasaurus says...

Sha Chancellor wrote:

 Why don't you use a foreach?


What distinct advantages does foreach have over for loops? Is it just 
syntatical sugar?


Basically, yes.


I looked at the dsource.org foreach tutorials and it seems you have to 
overload the opApply operator for classes?


Only if you want to do something like
class Foo ...
..
Foo f;
foreach(int i; f) {...}

Foo can be a custom container class, or something else. For example I have made
a permutation class:

foreach(char[] a; Permute("abcd")) writefln(a);

which outputs abcd, bacd, bcad, and so on.


I dunno the for loop just seems simpler and less confusing to me, and I 
don't see any clear advantages with using foreach. *enlighten me*


Then go ahead and use for loops. Foreach is just a somewhat cleaner way of
iterating arrays, since you don't have to specify start value and array length
explicitly. It also gives you a consistent way of iterating custom objects and
arrays alike.

Nick
Sep 13 2004
parent reply M <M_member pathlink.com> writes:
Sorry if this is a dumb question, but how you do something like this 

#int findc(char []s,chat c){





using foreach, not for?



In article <ci4pv1$313a$1 digitaldaemon.com>, Nick says...

In article <ci2en1$avj$1 digitaldaemon.com>, clayasaurus says...

Sha Chancellor wrote:

 Why don't you use a foreach?


What distinct advantages does foreach have over for loops? Is it just 
syntatical sugar?


Basically, yes.


I looked at the dsource.org foreach tutorials and it seems you have to 
overload the opApply operator for classes?


Only if you want to do something like
class Foo ...
..
Foo f;
foreach(int i; f) {...}

Foo can be a custom container class, or something else. For example I have made
a permutation class:

foreach(char[] a; Permute("abcd")) writefln(a);

which outputs abcd, bacd, bcad, and so on.


I dunno the for loop just seems simpler and less confusing to me, and I 
don't see any clear advantages with using foreach. *enlighten me*


Then go ahead and use for loops. Foreach is just a somewhat cleaner way of
iterating arrays, since you don't have to specify start value and array length
explicitly. It also gives you a consistent way of iterating custom objects and
arrays alike.

Nick
Sep 15 2004
parent Deja Augustine <deja scratch-ware.net> writes:
M wrote:


 Sorry if this is a dumb question, but how you do something like this 
 
 #int findc(char []s,chat c){




 
 using foreach, not for?
 
 



#int findc(char[] s, char c)






-Deja
Sep 15 2004