I have a query regarding a concept.
Are dynamic arrays in c# also called list? Or they are totally different?
C# does not have a dynamic array type. However, you can use a List as a dynamic array, given that it supports indexed access:
List<string> list = new List<string>();
list.Add("Hello");
list.Add("Goodbye");
Console.WriteLine(list[1]);
Take a look at Generic Lists.
Since it's the first link I found out when looking for this difference I would like to contribute a little.
The Nitin Bisht response is not entirely wrong, but by most of programming definitions a dynamic array is a type of array that can be set when the program is already running, simply put, it's size is set during run time not in compilation.
In C# this is written as:
string[] myDynamicArray;
myDynamicArray = SomeMethodThatReturnsAnCollection().ToArray();
Other way would be a method which returns an existing array like:
string[] myDynamicArray;
myDynamicArray = SomeMethodThatReturnsAnArray();
Those are Dynamic Arrays, you don't tell your program which size it has but inside the logic of that context this will be decided.
Those Arrays in C# has the Resize method, which enables the programmer to grow the array, which I believe it was the Nitin Bisht and so many others interpretation around that question, but this is a wrong assumption, resizable is different than dynamic.
Instead of using Resize in your Array, you could just use a List type, List in C# implements an Array in it's core, which can be seen here, but it also has the ability to grow in an easier approach than the Array implementation enables us with the Add(T item) List method.
List in C# would be a native Dynamic Resizable Array, some languages call similarly implementations of this structure as Vector, which are not a LinkedList with nodes and pointers for example.
Summarizing the difference in code:
var myList = new List<string> { "initial value" };
myList.Add("New value"); // After add, myList has this new value
var myArray = new string[] { "initial value" };
myArray.Append("New value") // after Append myArray doesnt have a new value
With Append() method what happens is another IEnumerable collection is created with the new value, so if you iterate through both collections you will see that the list prints out the new value but the array doesn't, in that case one way you can fix that is doing this:
string[] myArray;
myArray = myArray.Append("New value").ToArray(); // now it will work
The difference here is that myArray variable is being rewritten with the new array generated by .Append().ToArray() line, in the List example the Add() method will resize and then add the new value.
Important to note that this resize is done in a similar manner than what we did with the Append() "fixed" code, the List creates a new Array with increased size and copies it's original contents to this new Array.
You can use the resources given by the Array class to get to the same result as the Add() method implemented by List, but off course if you need that method you should just use an List instead of writing your own implementation, very rarely you would have to do it and to be honest your implementation would be probably less efficient than the already built ones.
In summary that is the difference between them, as you can see they have similarities but I would still treat them very differently.
Usually you wanna use an array when you do not expect to grow any further, if that is your case then an array is more useful since it's has less implementations and that brings a performance gain which can be good in a lot of scenarios.
If not, just use lists.
Using EF6 and SQL Server. This question is to ask if I am going in the right direction with my code.
Using a variety of SO posts I was able to define classes that contain lists and incorporate IComparable(Of T). Although the objects in the lists have properties that can be used for ordering such as dates, I need to maintain a user-defined order that is solely determined by how the user wants the objects arranged.
My first assumption is that I have to maintain a distinct property to maintain the user-defined order. Is that correct? This is a very simplified example of what I currently have defined:
Class Parent
:
Public Property SomeList as List(Of Something)
End Class
Class Something
Implements IComparable(of Something)
:
public property PositionInList as Integer
Public Function CompareTo(that As Something) As Integer ...
Return PositionInList.CompareTo(that.PositionInList)
End Function
End Class
And if I write the following:
dim aList as New List(Of Something)
aList = Parent.SomeList
aList.Sort()
...alist is sorted based on PositionInList as I expected.
If I want to insert a new record into the list, am I responsible for changing the values of PositionInList throughout all the objects in the list? The reason I ask is because the LINQ command of the form .insert(index,object) indicates it inserts an element into the List(Of T) at the specified index. And as I look at the table after the .insert(index,object) prior to SaveChanges(), the list does have the new object in the correct location, but it didn't set PositionInList to the value of the index specified in .insert(index,object). Is it supposed to and I haven't coded things correctly? Also, PositionInList is going to have to ripple the change throughout all the objects - am I responsible for that?
Are there predefined methods I need to learn that would manipulate PositionInList when I insert?
I will also want the user to be able to move items to new positions in the lists. Are there patterns to do this kind of thing, or once again is that pretty much up to me?
Added per request in comment below:
The application is divided into 3 layers: UI, domain, storage. The storage layer includes a storage service class which has the CRUD methods that interface to the SQL Server.
This is one of the current Create methods. At present it only appends a record at the end of the list. Per your comment, I will modify it to update PositionInList when the call to create requests an insertion somewhere inside the list. That will require additional parameters not currently coded in the method.
Public Overrides Sub ElementCreate(DomainElement As DomainElement)
Dim aSqlElement As New SqlElement
aSqlElement.DomainToSqlElement(DomainElement)
Dim theParent = SqlContext.SqlContents.Include("ContentElements").Where(Function(x) x.ID = aSqlElement.ContentID).SingleOrDefault()
theParent.ContentElements.Add(aSqlElement)
SqlContext.SaveChanges()
End Sub
You can use a SortedSet instead so that you don't have to re-sort.
Class Parent
:
Public SortedSet<Something> SomeList = new SortedSet<Something>(
new FuncComparer<Something>( (a, b) => a.PositionInList.CompareTo(b.PositionInList ) ));
End Class
I am playing around with OOP in MATLAB, and I have the following constructor:
function obj = Squadron(num_fighters, num_targets, time_steps)
if nargin == 0
num_targets = 100;
time_steps = 100;
num_fighters = 10;
end
obj.num_shooters = num_fighters;
for iShooter = 1:obj.num_shooters
a(iShooter) = Shooter(num_targets, time_steps);
end
obj.ShooterArray = a;
obj.current_detections = zeros(num_fighters, num_targets);
end
That temporary variable 'a' smells terrible. Is there a better way to initialize an array of objects, I wish there was a push/pop method. I am sure there is a better way to do this.
Looks like you are trying to create an array of handle objects (Shooters) and store it inside the property of another handle object (a Squardron). I have had a very similar problem discussion that might help you.
In short: What you are doing might not be pretty - but might be pretty good already.
When creating an array in Matlab it is usually a good Idea to do some pre-allocation to reserve memory which speeds up performance significantly.
In a normal case something like this:
a=zeros(1,1000);
for n=1:1000
a(n)=n;
end
(here a=1:1000; would be even better)
For objects the pre-allocation works by assigning one of the objects to the very last field in the array. Matlab then fills the other fields before that with objects (handles) that it creates by calling the constructor of that object with no arguments (see Matlab help). Hence a pre-allocation for objects could look like this:
a(1,1000)=ObjectConstructor();
for n=1:1000
a(n)=ObjectConstructor();
end
or simply
for n=1000:-1:1
a(n)=ObjectConstructor();
end
Making sure Shooter can be called with no arguments you should be able to do something like:
for iShooter = obj.num_shooters:-1:1
obj.ShooterArray(iShooter) = Shooter(num_targets, time_steps);
end
However, it turns out that for some reason this direct storing of an array of objects in another object's property creates very bad performance. (Probably the array pre-allocation does not work well in this case). Hence using an auxiliary variable and allocating the full array at once to the property is in this case is a good idea to increase performance.
I would try:
for iShooter = obj.num_shooters:-1:1
a(iShooter) = Shooter(num_targets, time_steps);
end
obj.ShooterArray = a;
Again - for more detail see this discussion
There are a couple of ways to handle this situation...
Building object arrays in the constructor:
You could modify your Shooter class such that when you pass arrays of values it creates an array of objects. Then you could initialize ShooterArray like so:
obj.ShooterArray = Shooter(repmat(num_targets,1,num_fighters),...
repmat(time_steps,1,num_fighters));
Replicating instances of a value class:
If Shooter is a value class, and each object is going to be exactly the same (i.e. you don't initialize any of its default properties to random values), then you can create just one object and replicate it using REPMAT:
obj.ShooterArray = repmat(Shooter(num_targets,time_steps),1,num_fighters);
Unfortunately, if Shooter is a subclass of the handle class, you can't just replicate it as you can with a value class. You would actually be replicating references to just one object, when you really need a number of separate objects each with their own unique reference. In such a case, your current code is likely the best solution.
Question: I am wondering which is the optimal solution for dealing with Arrays in Excel 2003 VBA
Background: I have a Macro in Excel 2003 that is over 5000 lines. I have built it over the last 2 years adding new features as new Procedures, which helps to segment the code and debug, change, or add to that feature. The downside is that I am using much of the same base information in multiple procedures, which requires me to load it into arrays with minor differences multiple times. I am now running into issues with the length of run time, so I am now able to do a full rewrite.
This file is used to grab multiple items of manufacturing flows (up to 4 different set ups with a total of up to 10 distinct flows , of up to 1000 steps each) with the information being Flow specific, Sub-Flow specific for grouping / sorting purposes, and Data (such as movements, inventory, CT, ...)
It then will stick the data onto multiple sheets used to manage the process utilizing data sheets to be perused, charts, and Cell Formatting to denote process flow capability / history.
The Flow is in the Excel File, while the Manufacturing data is read in with 7 different OO4O Oracle SQL pulls, some reused multiple times
The Arrays are:
arrrFlow(1 to 1000, 1 to 4) as a Record Type with 4 strings
arrrSubFlow(1 to 1000, 1 to 10) as a Record Type with 4 strings, 2 integers, and 1 single
arrrData(1 to 1000, 1 to 10) as a Record Type with 1 string, 4 integers, 12 longs, and 1 single
arriSort(1 to 1000, 1 to 4) as Integer (Used as a pointer Array to sort the Flow, Sub Flow, and Data in a Group, Sub Group, and Step order while leaving the original arrays in Step order)
Possibilities:
1) Rewrite the macro into one big procedure that loads the data into master arrays dimensioned within the Procedure once
Pro: Dimensioned in the Procedure rather than as a Public Variable in the Module and not passed.
Con: Harder to debug with one mega procedure instead of multiple smaller ones.
2) Keep macro with multiple procedures but passing the Arrays
Pro: Easier to debug code with multiple smaller procedures.
Con: Passing Arrays (Expensive?)
3) Keep macro with multiple procedures but with the Arrays being Public Dim'ed variables in the Module
Pro: Easier to debug code with multiple smaller procedures.
Con: Public Arrays (Expensive?)
So, what's the community's verdict? Does anyone know the expense of using Public Arrays vs Passing Arrays? Is the Cost of either of these worth losing the ease of having my procedures being focused on one feature?
UPDATE:
I load Inventory Data at a discrete level (multiple per Step), Moves Data at a aggregate level (one per step), and the Beginning of Shift Inventory at an aggregate level. I aggregate the Inventory data by step placing it in Work State categories (Run, Wait,...) I create targets off data already on the sheets.
I have a Flow sheet that shows the Work Flows by Type, currently 3 products have a similar but not exactly the same flow, and 2 products are a different flow, that are similar but again not the same as each other. I have assigned each set of steps in the different flows a group and sub-group.
I place this data on multiple sheets, some in Step Order, some in group / sub-group order. I also need the data summed up by group and product, group / sub-group and product, portion of the line and product, and product.
I use Record Types so I actually have a readable three dimensional array, arrSubFlow(1,1).strStep (Step Name of the 1st Step of the 1st Device), arrData(10,5).lngYest (Yesterday's movement for the 10th Step of the 5th Device).
My main point of optimization is going to be in the section where I create 10 pages from scratch every single time. With Merging Cells, Borders, Headers, ... This is a very time consuming process. I will add a section that will compare my data with the page to see if it needs to be changed and if so, only then recreate it otherwise, I'll clear each section of data and only write data that changes to the sheet. This will be huge, based on my time logging data. However, whenever I update code, I always try to improve other aspects of the code as well. I see the loading of the data into a Structure (Array, RecordSet, Collection) once as both a little bit of optimization, but more so for data integrity, so I do not have the opportunity to load it differently for different sheets.
The main issues I see getting away from Arrays right now are:
* Already heavily invested in them, but this is not a good enough reason to not change
* Don't know if there is much cost to passing them, since it will by ByRef
* I use a Sort Function to create a Sorted "Pointer" array that lets me leave the Array in Step Flow order, while easily referencing it by Group / Sub-group order.
Since I am always trying to make my code for now and the future, I am not against updating the arrays to either RecordSets or Collections, but not merely for the sake of changing them to learn something cool. My arrays work and from my research, they add seconds to the run time, not substantial amounts for this 2 minute report. So If another structure is easier to update in the future than Two-dimensional Arrays of Record Types, then please let me know, but does anyone know the cost of passing an Array to a procedure, assuming you are not doing a ByVal pass?
You've provided a good bit of detail, but it's still quite difficult to understand exactly what's going on without seeing some code. In your question, I can identify at least 4 big topics that you interweave throughout: Manufacturing, Data Access, VBA, and Coding Best-Practices. It's hard for me to tell exactly what you're asking because your question scope is huge. Either way, I appreciate your trying to write better code in VBA.
It's hard for me to understand exactly what you plan to do with the arrays. You say:
The downside is that I am using much of the same base information in multiple procedures, which requires me to load it into arrays with minor differences multiple times.
I'm not sure what you mean here. Are you using arrays to represent a row of data that you retrieved from a database? If so, you might consider using class modules instead of the usual "macro" modules. These will allow you to work with full-blown objects instead of arrays of values (or references, as the case may be). Classes take more work to set up and consume, but they make your code a lot easier to work with and will greatly help you to segment your code.
As user Emtucifor already pointed out, there may be objects such as ADO Recordset objects (which may require Access to be installed...not sure) that can help greatly. Or you might create your own.
Here's a long example of how using a class might help you. Although this example is lengthy, it will show you how a few principles of object-oriented programming can really help you clean up your code.
In the VBA editor, go to Insert > Class Module. In the Properties window (bottom left of the screen by default), change the name of the module to WorkLogItem. Add the following code to the class:
Option Explicit
Private pTaskID As Long
Private pPersonName As String
Private pHoursWorked As Double
Public Property Get TaskID() As Long
TaskID = pTaskID
End Property
Public Property Let TaskID(lTaskID As Long)
pTaskID = lTaskID
End Property
Public Property Get PersonName() As String
PersonName = pPersonName
End Property
Public Property Let PersonName(lPersonName As String)
pPersonName = lPersonName
End Property
Public Property Get HoursWorked() As Double
HoursWorked = pHoursWorked
End Property
Public Property Let HoursWorked(lHoursWorked As Double)
pHoursWorked = lHoursWorked
End Property
The above code will give us a strongly-typed object that's specific to the data with which we're working. When you use multi-dimension arrays to store your data, your code resembles this: arr(1,1) is the ID, arr(1,2) is the PersonName, and arr(1,3) is the HoursWorked. Using that syntax, it's hard to know what is what. Let's assume you still load your objects into an array, but instead use the WorkLogItem that we created above. This name, you would be able to do arr(1).PersonName to get the person's name. That makes your code much easier to read.
Let's keep moving with this example. Instead of storing the objects in array, we'll try using a collection.
Next, add a new class module and call it ProcessWorkLog. Put the following code in there:
Option Explicit
Private pWorkLogItems As Collection
Public Property Get WorkLogItems() As Collection
Set WorkLogItems = pWorkLogItems
End Property
Public Property Set WorkLogItems(lWorkLogItem As Collection)
Set pWorkLogItems = lWorkLogItem
End Property
Function GetHoursWorked(strPersonName As String) As Double
On Error GoTo Handle_Errors
Dim wli As WorkLogItem
Dim doubleTotal As Double
doubleTotal = 0
For Each wli In WorkLogItems
If strPersonName = wli.PersonName Then
doubleTotal = doubleTotal + wli.HoursWorked
End If
Next wli
Exit_Here:
GetHoursWorked = doubleTotal
Exit Function
Handle_Errors:
'You will probably want to catch the error that will '
'occur if WorkLogItems has not been set '
Resume Exit_Here
End Function
The above class is going to be used to "do something" with a colleciton of WorkLogItem. Initially, we just set it up to count the total number of hours worked. Let's test the code we wrote. Create a new Module (not a class module this time; just a "regular" module). Paste the following code in the module:
Option Explicit
Function PopulateArray() As Collection
Dim clnWlis As Collection
Dim wli As WorkLogItem
'Put some data in the collection'
Set clnWlis = New Collection
Set wli = New WorkLogItem
wli.TaskID = 1
wli.PersonName = "Fred"
wli.HoursWorked = 4.5
clnWlis.Add wli
Set wli = New WorkLogItem
wli.TaskID = 2
wli.PersonName = "Sally"
wli.HoursWorked = 3
clnWlis.Add wli
Set wli = New WorkLogItem
wli.TaskID = 3
wli.PersonName = "Fred"
wli.HoursWorked = 2.5
clnWlis.Add wli
Set PopulateArray = clnWlis
End Function
Sub TestGetHoursWorked()
Dim pwl As ProcessWorkLog
Dim arrWli() As WorkLogItem
Set pwl = New ProcessWorkLog
Set pwl.WorkLogItems = PopulateArray()
Debug.Print pwl.GetHoursWorked("Fred")
End Sub
In the above code, PopulateArray() simply creates a collection of WorkLogItem. In your real code, you might create class to parse your Excel sheets or your data objects to fill a collection or an array.
The TestGetHoursWorked() code simply demonstrates how the classes were used. You notice that ProcessWorkLog is instantiated as an object. After it is instantiated, a collection of WorkLogItem becomes part of the pwl object. You notice this in the line Set pwl.WorkLogItems = PopulateArray(). Next, we simply call the function we wrote which acts upon the collection WorkLogItems.
Why is this helpful?
Let's suppose your data changes and you want to add a new method. Suppose your WorkLogItem now includes a field for HoursOnBreak and you want to add a new method to calculate that.
All you need to do is add a property to WorkLogItem like so:
Private pHoursOnBreak As Double
Public Property Get HoursOnBreak() As Double
HoursOnBreak = pHoursOnBreak
End Property
Public Property Let HoursOnBreak(lHoursOnBreak As Double)
pHoursOnBreak = lHoursOnBreak
End Property
Of course, you'll need to change your method for populating your collection (the sample method I used was PopulateArray(), but you probably should have a separate class just for this). Then you just add your new method to your ProcessWorkLog class:
Function GetHoursOnBreak(strPersonName As String) As Double
'Code to get hours on break
End Function
Now, if we wanted to update our TestGetHoursWorked() method to return result of GetHoursOnBreak, all we would have to do as add the following line:
Debug.Print pwl.GetHoursOnBreak("Fred")
If you passed in an array of values that represented your data, you would have to find every place in your code where you used the arrays and then update it accordingly. If you use classes (and their instantiated objects) instead, you can much more easily update your code to work with changes. Also, when you allow the class to be consumed in multiple ways (perhaps one function needs only 4 of the objects properties while another function will need 6), they can still reference the same object. This keeps you from having multiple arrays for different types of functions.
For further reading, I would highly recommend getting a copy of VBA Developer's Handbook, 2nd edition. The book is full of great examples and best practices and tons of sample code. If you're investing a lot of time into VBA for a serious project, it's well worth your time to look into this book.
It sounds like maybe Excel and arrays are not the best tools for the job you're doing. If you could please explain a little bit about the type of data that you're working with and what you're doing, that will really help provide a better answer. Give as much detail as you can about the types of manipulations you're doing on the data and what the inputs and outputs are.
I'm going to give some highlights that I think will help you, and then may edit my answer to be more complete as I get responses from you, and so I have more time to flesh things out a bit.
There is an object that naturally handles the record-type objects you're working with called a Recordset. In the VBA editor, go to Tools -> References and add Microsoft ActiveX Data Objects 2.X Library (the highest one on your machine). You can declare an object of type ADODB.Recordset, then do Recordset.Fields.Append to add fields to it, then .Open it and finally .AddNew, set field values, and .Update. This is a natural object to pass around in programs as an input or output parameter. It has natural traversal and positioning functions (.Eof, .Bof, .AbsolutePosition, .MoveNext, .MoveFirst, .MovePrevious) and supports searching and filtering (.Filter = "Field = 'abc'", .Find and so on).
I don't recommend using public variables, though without an understanding of what you're doing I can't really advise you well here.
I also would avoid one big procedure. Code should be broken out into reusable functional units that do only one thing, whose names are essentially self-documenting about what they do.
If you want to improve the performance of your code, hit ctrl-break at random times while it's running and break into the code. Then press Ctrl-L to view the call stack. Make a note of what is in the list each time. If any item shows up a majority of the time, it is the bottleneck and is where you should spend your time trying to optimize it. However, I don't advise trying to optimize what you have until you make some higher-level decisions (like whether you will switch to a recordset).
I really need more information to help you better.
If you're interested, I'll work up some demonstration code that will show how useful the Recordset object is. Inserting the data from a Recordset into an Excel range is super easy with Recordset.GetRows or .GetString (though some array transposition may be required, that's not hard, either).
UPDATE: If your goal is to speed up your process, then before doing anything I think it's best to be armed with the knowledge of what is taking the most time. Would you please hit ctrl-break about 10 times and note down the call stack each time, then tell me what the most common items in the call stack are?
In terms of updating the speed of cell formatting, here's my experience:
Merge is the slowest operation you can possibly do. Try to avoid it if at all possible. Using "center across selection" is one alternative. Another is just not merging, but using some combination of sizing properly, borders, cell background color, and turning off gridlines for the entire workbook.
Apply borders or other formatting once to the largest thing possible instead of to many small things such as cell by cell. For example, if most cells have all borders but some don't, then apply all borders to the entire range and during your looping remove the ones you don't want. And even then, try to do entire rows and larger ranges.
Save a template file with borders and formatting already applied. Let's say you put one row in it with the formatting for a certain section. In one step duplicate that row into as many rows are needed for that section, say 20 rows, and they will all have the same formatting. Duplicating rows is MUCH faster than applying formatting cell by cell.
Also, I wouldn't automatically go for using classes. While OO is great and I do it myself (heck, I just built 8 classes for something the other day to model a hierarchical structure so I could easily expose the parts of it when I needed them), in practice it can be slower. A simple set of public variables in a class is faster than using getters and setters. A user defined Type is even faster than a class, but you can run into gotchas trying to pass around UDTs in classes (they have to be declared in a non-class public module and even then they can give problems).
I have an array in Scala with the class ArrayBuffer[Actor], where Actor is a class that implements the Ordered[Actor] trait. How do I sort this array without coding it manually?
I know there is an object called Sorting, but it doesnt seem to work since ArrayBuffer doesn't implement/extend the right classes.
How do I sort ArrayBuffer[A] type arrays?
If you are using Scala 2.8, you could use the sortWith method of the ArrayBuffer[T] class, which is inherited from the SeqLike trait.
The following code snippet sorts an ArrayBuffer[T] object in ascending order:
def ascendingSort[T <% Ordered[T]](xs: ArrayBuffer[T]) = xs.sortWith(_ < _)
Note that this does not mutate the actual ArrayBuffer, but creates a new one with the elements in the right order.
If you are using Scala 2.7, you could use the stableSort method of the Sorting object. This takes the elements of the ArrayBuffer and produces an array of elements sorted in the right order (given by a closure as an argument, ascending as a default).
For example:
val a = new scala.collection.mutable.ArrayBuffer[Int]()
a += 5
a += 2
a += 3
scala.util.Sorting.stableSort(a)
The important question is what do you want to do with the ArrayBuffer. Usually, a Buffer is used internally in different algorithms in order to increase the performance of intermediate results. If you are using it for that, have a look at the ways of sorting the collection you want to return at the end of your algorithm. The Sorting object already provides a way of transforming an ArrayBuffer into a sorted Array.
From the scaladoc of the Buffer class:
Buffers are used to create sequences of elements incrementally
As you are using it with Actors, it might be used for some kind of actor queue - in which case, you might want to have a look at the Queue collection.
Hope it helps,
-- Flaviu Cipcigan
Btw, the Actor class here is my own class used for "Actors" in a world created using my new game engine for scala ("Awesome Game Engine for Scala ~ AGES"), so it has nothing to do with the concurrency actor class. Also, implementations of lists in scala are a jungle, everything is either deprecated or implemented in a lot of different ways...ArrayBuffer works for my need (my need being a variable size array for containing actors).
Hope this clarifies :)