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Check whether a string array contains an item (without a loop)
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| Total Hit (2631) |
To determine whether a String array contains a given item it seems that you can't avoid writing a loop. However, you can do it with just one line of code, using the new VB6 Join function:
«Code LangId=1»
' ARR is an array of string, SEARCH is the value to be searched
Found = InStr(1, vbNullChar
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Count Sort, a special case of indexed sort
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| Total Hit (2932) |
CountSort is yet another sort algorithm, which can be applied only under very particular conditions but that, when such conditions are met, turns to be the fastest of the lot. Count Sort can be used when the key is of Integer type, or when it is of Long type but the range of values is not too large.
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Polymorphic array procedures
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| Total Hit (2328) |
You can create "polymorphic" routines that work with any type of array (except arrays of fixed-length strings, or UDTs) by using Variant parameters. Take for example the following code:
«Code LangId=1»
Function Sum(arr As Variant) As Variant
Dim i As Long
For i = LBound(arr) To UBound(
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Quickly clear a portion of an array
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| Total Hit (2858) |
The fastest way to clear an array is to ReDim (if the array is dynamic) or Erase it (if the array is Static). However, if you want to clear a portion of an array, it seems that you must code a For-Next loop.
If you are dealing with numeric arrays, there is a faster alternative, based on the ZeroM
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Quickly initialize Variant and String arrays
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| Total Hit (3456) |
Visual Basic doesn't provide any way to declare an array and initialize its elements at the same time. In most cases you end up with setting individual elements one by one, as in:
«Code LangId=1»
Dim strArray(0 To 3) As String
strArray(0) = "Spring"
strArray(1) = "Summer"
strArray(2) = "Fall"
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Scan all the items in a multi-dimensional array with only one loop
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| Total Hit (2454) |
It seems that you need two nested For loops to iterate over all the elements of a 2-dimensional array, and three loops for a 3-dimensional array, and so on. However, the For Each loop offers you a neat and concise solution, as this code proves:
«Code LangId=1»
' a 2-dimensional array of Strings
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Simple variables are always faster than array elements
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| Total Hit (2787) |
Reading and writing an item of an array is always slower than accessing a simple variable. Therefore, if you need to repeatedly use the same array item in a loop, you should assign it to a temporary variable and use that variable instead. I've included an example of this technique that scans an Inte
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Sorting on multiple keys
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| Total Hit (2338) |
Frequently you need to sort arrays of records using multiple keys. This may be required since one single key does not uniquely identify a record (e.g. you may need both LastName and FirstName to select a given employee in a large company where people with same name work), or it may be necessary for
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Speed up searches with hash tables
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| Total Hit (3044) |
You probably know that there are basically two methods to search a value in an array: the brute force approach (i.e. linear searching) and the binary search. Both of them have disadvantages: when the array counts N items, linear searching requires N/2 comparisons on the average for successful search
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The number of dimensions of an array
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| Total Hit (4100) |
Using "pure" VB, the only way to build a generic routine that returns the number of dimensions of an array passed as an argument is using a loop that repeatedly tests the LBound (o UBound) function until it fails:
«Code LangId=1»
Function ArrayDims(arr As Variant) As Integer
Dim i As Intege
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Undocumented trick to speed up functions that return array
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| Total Hit (2667) |
VB6 functions can return an array. Unlike regular functions that return scalar values or objects, however, you can't use the name of the function as a local variable where to store intermediate result, and you are forced to work with a temporary local array, and then assign this array to the Functio
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ArrayAny - Return an initialized array of any type
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| Total Hit (2110) |
«Code LangId=1»
' Returns an array and initializes it with passed data.
'
' It is similar to the Array function, but it works with
' array of any type. The type of the returned array is
' assumed to be the type of the first element in the
' parameter list, so you might need to force a given
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ArrayAvg - The average of an array of any type
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| Total Hit (2156) |
«Code LangId=1»
' The average of an array of any type
'
' FIRST and LAST indicate which portion of the array
' should be considered; they default to the first
' and last element, respectively
' if IGNOREEMPTY argument is True or omitted,
' Empty values aren't accounted for
Function ArrayA
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ArrayShuffle - Randomize the order of elements in an array
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| Total Hit (3492) |
«Code LangId=1»
' Shuffle the elements of an array of any type
' (it doesn't work with arrays of objects or UDT)
Sub ArrayShuffle(arr As Variant)
Dim index As Long
Dim newIndex As Long
Dim firstIndex As Long
Dim itemCount As Long
Dim tmpValue As Variant
firs
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ArrayStdDev - The standard deviation of a numeric array
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| Total Hit (3234) |
«Code LangId=1»' The standard deviation of an array of any type
'
' if the second argument is True or omitted,
' it evaluates the standard deviation of a sample,
' if it is False it evaluates the standard deviation of a population
'
' if the third argument is True or omitted, Empty values are
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ArraySum - The sum of all the items in an array of any type
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| Total Hit (2475) |
«Code LangId=1»
' Return the sum of the values in an array of any type
' (for string arrays, it concatenates all its elements)
'
' FIRST and LAST indicate which portion of the array
' should be considered; they default to the first
' and last element, respectively
Function ArraySum(arr As
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BubbleSort - Sort Arrays using the BubbleSort Algorithm
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| Total Hit (3096) |
«Code LangId=1»
' Bubble Sort an array of any type
' BubbleSort is especially convenient with small arrays (1,000
' items or fewer) or with arrays that are already almost sorted
'
' NUMELS is the index of the last item to be sorted, and is
' useful if the array is only partially filled.
'
'
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CBitArray - a class for dealing with large arrays of Boolean
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| Total Hit (2389) |
«Code LangId=1»
' ------------------------------------------------------------------------
' The CBITARRAY class
'
' simiulates an array of Boolean values
' saves memory by packing one element in one bit
'
' IMPORTANT: you make make ITEM the default member for this class
' do
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CombSort - A very efficient algorithm
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| Total Hit (2297) |
«Code LangId=1»' Comb Sort an array of any type
'
' CombSort is faster than all but QuickSort and close to it.
' On the other hand, the code is much simpler than QuickSort
' and can be easily customized for any array type
' This routine is based on an article appeared on the Byte
' magazine i
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Filter - A replacement for VB6's Filter function under VB5
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| Total Hit (2186) |
«Code LangId=1»' A replace for the Filter function under VB4 and VB5
'
' Note that the source array is modified. For this reason
' this is declared as a Sub rather than a Function
Sub Filter(arr() As String, ByVal Search As String, Optional ByVal Include As _
Boolean, Optional ByVal Comp
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FilterDuplicates - Delete duplicate items in an array
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| Total Hit (2225) |
«Code LangId=1»
' Filter out duplicate values in an array and compact
' the array by moving items to "fill the gaps".
' Returns the number of duplicate values
'
' it works with arrays of any type, except objects
'
' The array is not REDIMed, but you can do it easily using
' the following co
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TransposeMatrix - Rotate a bi-dimensional array
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| Total Hit (2330) |
«Code LangId=1»
' evaluate the transposed matrix
'
' a transposed matrix is the array you get when
' you "rotate" a bi-dimensional array
Function TransposeMatrix(arr() As Double) As Double()
Dim startRow As Long, startCol As Long
Dim endRow As Long, endCol As Long
Dim r As Lon
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HasDuplicateValues - Check if an array has duplicate values
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| Total Hit (2611) |
«Code LangId=1»' Returns True if an array contains duplicate values
' it works with arrays of any type
Function HasDuplicateValues(arr As Variant) As Boolean
Dim col As Collection, index As Long
Set col = New Collection
' assume that the array contains duplicates
HasDu
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ListBoxEnsureVisible - Ensure that a ListBox element is visible
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| Total Hit (2263) |
«Code LangId=1»' ensure that a listbox item is visible
' if the second argument is omitted, the index of current item is used
'
' NOTE: uses the ListBoxVisibleItems function
Sub ListBoxEnsureVisible(lst As ListBox, Optional ByVal itemIndex As Long = -1)
Dim visibleCount As Long
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