Set: Difference between revisions
→{{header|VBA}}: Collection as set
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puts "cardinality: [struct::set size $s3]</lang>
=={{header|VBA}}==
<lang vb>'Implementation of "set" using the built in Collection datatype.
'A collection can hold any object as item. The examples here are only strings.
'A collection stores item, key pairs. With the key you can retrieve the item.
'The keys are hidden and cannot be changed. No duplicate keys are allowed.
'For the "set" implementation item is the same as the key. And keys must
'be a string.
Private Function createSet(t As Variant) As Collection
Dim x As New Collection
For Each elem In t
x.Add elem, elem
Next elem
Set createSet = x
End Function
Private Function isElement(s As Variant, x As Collection) As Boolean
Dim errno As Integer, t As Variant
On Error GoTo err
t = x(s)
isElement = True
Exit Function
err:
isElement = False
End Function
Private Function setUnion(A As Collection, B As Collection) As Collection
Dim x As New Collection
For Each elem In A
x.Add elem, elem
Next elem
For Each elem In B
On Error Resume Next 'Trying to add a duplicate throws an error
x.Add elem, elem
Next elem
Set setUnion = x
End Function
Private Function intersection(A As Collection, B As Collection) As Collection
Dim x As New Collection
For Each elem In A
If isElement(elem, B) Then x.Add elem, elem
Next elem
For Each elem In B
If isElement(elem, A) Then
On Error Resume Next
x.Add elem, elem
End If
Next elem
Set intersection = x
End Function
Private Function difference(A As Collection, B As Collection) As Collection
Dim x As New Collection
For Each elem In A
If Not isElement(elem, B) Then x.Add elem, elem
Next elem
Set difference = x
End Function
Private Function subset(A As Collection, B As Collection) As Boolean
Dim flag As Boolean
flag = True
For Each elem In A
If Not isElement(elem, B) Then
flag = False
Exit For
End If
Next elem
subset = flag
End Function
Private Function equality(A As Collection, B As Collection) As Boolean
Dim flag As Boolean
flag = True
If A.Count = B.Count Then
For Each elem In A
If Not isElement(elem, B) Then
flag = False
Exit For
End If
Next elem
Else
flag = False
End If
equality = flag
End Function
Private Function properSubset(A As Collection, B As Collection) As Boolean
Dim flag As Boolean
flag = True
If A.Count < B.Count Then
For Each elem In A
If Not isElement(elem, B) Then
flag = False
Exit For
End If
Next elem
Else
flag = False
End If
properSubset = flag
End Function
Public Sub main()
'Set creation
Dim s As Variant
Dim A As Collection, B As Collection, C As Collection
s = [{"Apple","Banana","Pear","Pineapple"}]
Set A = createSet(s) 'Fills the collection A with the elements of s
'Test m ? S -- "m is an element in set S"
Debug.Print isElement("Apple", A) 'returns True
Debug.Print isElement("Fruit", A) 'returns False
'A ? B -- union; a set of all elements either in set A or in set B.
s = [{"Fruit","Banana","Pear","Orange"}]
Set B = createSet(s)
Set C = setUnion(A, B)
'A n B -- intersection; a set of all elements in both set A and set B.
Set C = intersection(A, B)
'A \ B -- difference; a set of all elements in set A, except those in set B.
Set C = difference(A, B)
'A ? B -- subset; true if every element in set A is also in set B.
Debug.Print subset(A, B)
'A = B -- equality; true if every element of set A is in set B and vice versa.
Debug.Print equality(A, B)
'Proper subset
Debug.Print properSubset(A, B)
'Modify -remove an element by key
A.Remove "Apple"
'Modify -remove the first element in the collection/set
A.Remove 1
'Add "10" to A
A.Add "10", "10"
End Sub</lang>
=={{header|zkl}}==
A simplistic implementation that is fine for smallish sets
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