CompMathBSc, English 5 October 2006 Programming basics — continued  Arrays  Cycle Statements: Loops  Control Structures vs Conditions  Subs: Procedures and Functions  File and data management (I/O)  Using the Object Browser  First look on the IDE Programming basics — continued  Arrays  Cycle Statements: Loops  Control Structures vs Conditions  Subs: Procedures and Functions  File and data management (I/O)  Using the Object Browser  First look on the IDE

2/38 Constants (remark)  Convention: use BLOCK letters to name constants  e.g. Dim MYCONST = 100  easily recognised  Convention: use BLOCK letters to name constants  e.g. Dim MYCONST = 100  easily recognised

3/38 ArraysArrays  Problem: individual values that should be stored together  data of the same type  e.g. names of people in a class  Solutions: 1. User-defined type (looser) 2. Collection (even more looser) 3. Array (tight) – a special collection  Problem: individual values that should be stored together  data of the same type  e.g. names of people in a class  Solutions: 1. User-defined type (looser) 2. Collection (even more looser) 3. Array (tight) – a special collection

4/38 Types of Arrays Like by variables:  Integer, Long -- usual  Single, Double  String  Boolean –- rare  Variant -- very rare = types of values stored in the array  must be of the same type Like by variables:  Integer, Long -- usual  Single, Double  String  Boolean –- rare  Variant -- very rare = types of values stored in the array  must be of the same type

5/38 Dimensions – 1D, 2D,...  1D array of 100: [1.00;2.82;3.63;4.11;..;100.75]  2D array of (3;5): [ ] = 3 rows and 5 columns --> 3x5 matrix  3D array: a cube  4D, 5D, 6D... (rare)  1D array of 100: [1.00;2.82;3.63;4.11;..;100.75]  2D array of (3;5): [ ] = 3 rows and 5 columns --> 3x5 matrix  3D array: a cube  4D, 5D, 6D... (rare)

6/38 DeclarationDeclaration  Syntax: Dim MyArray(100) As Single Dim My2DArray(3,5) As Integer  and also: Dim MyArray(1 to 25) As Single Dim My2DArray(3, 8 to 12) As Integer  UBound(), LBound()  Option Base 1  Syntax: Dim MyArray(100) As Single Dim My2DArray(3,5) As Integer  and also: Dim MyArray(1 to 25) As Single Dim My2DArray(3, 8 to 12) As Integer  UBound(), LBound()  Option Base 1

7/38 ElementsElements  just like individual variables  identified by an index e.g. ReadElement = MyArray(12)  ReadElement must be a variable of the right type  MyArray must have an index of 12  ‘Subscript out of range’  just like individual variables  identified by an index e.g. ReadElement = MyArray(12)  ReadElement must be a variable of the right type  MyArray must have an index of 12  ‘Subscript out of range’

8/38 Value assignment  I want the element of index 5 to be 8.314: MyArray(5) =  with a string array: MyStringArray(5) = ”8.314”  filling up an array: with cycles (loops)  use For.. Next  I want the element of index 5 to be 8.314: MyArray(5) =  with a string array: MyStringArray(5) = ”8.314”  filling up an array: with cycles (loops)  use For.. Next

9/38 Dinamic Arrays Problem: I don’t know the size of the array I need in design-time (depends on user input) Solution: redimensioning Syntax: first:Dim MyDinArray() later:ReDim MyDinArray(Rows, Cols) where Rows & Cols are variables (!) = an elastic bag :) Problem: I don’t know the size of the array I need in design-time (depends on user input) Solution: redimensioning Syntax: first:Dim MyDinArray() later:ReDim MyDinArray(Rows, Cols) where Rows & Cols are variables (!) = an elastic bag :)

10/38 LoopsLoops  Use-case: a block of statements must be repeated many times  Loop types:  For.. Next --> I have a fix number (e.g. 25)  Do.. Loop --> I have a limiting condition  Use-case: a block of statements must be repeated many times  Loop types:  For.. Next --> I have a fix number (e.g. 25)  Do.. Loop --> I have a limiting condition

11/38 For.. Next  to run a block of statements a definite number of times e.g. 25  e.g. to fill up an array For CurrentIndex = 1 To 32 MyArray(CurrentIndex) = CurrentIndex – 1 Next CurrentIndex  to run a block of statements a definite number of times e.g. 25  e.g. to fill up an array For CurrentIndex = 1 To 32 MyArray(CurrentIndex) = CurrentIndex – 1 Next CurrentIndex

12/38 For.. Next  Syntax example: For Count = 1 To 25 [statement1] [statement2]... [statementN] Next Count  Syntax example: For Count = 1 To 25 [statement1] [statement2]... [statementN] Next Count

13/38 For.. Next  Stepping up (Step 2) or down (Step -2): For Count = 1 To 30 Step 2 ’run 15 times [statement1] [statement2]... [statementN] Next Count  Stepping up (Step 2) or down (Step -2): For Count = 1 To 30 Step 2 ’run 15 times [statement1] [statement2]... [statementN] Next Count

14/38 Do.. Loop  to run a block of statements an indefinite number of times  evaluates a condition to determine whether or not to continue running  types: 1.evaluates at the start  While / Until 2.evaluates at the end  While / Until  to run a block of statements an indefinite number of times  evaluates a condition to determine whether or not to continue running  types: 1.evaluates at the start  While / Until 2.evaluates at the end  While / Until

15/38 Do.. Loop (1.)  Syntax: (! logically opposites !) Do While [Condition=True] [block of statements] Loop Do Until [Condition=True] [block of statements] Loop  Syntax: (! logically opposites !) Do While [Condition=True] [block of statements] Loop Do Until [Condition=True] [block of statements] Loop

16/38 Do.. Loop (2.)  Syntax: (! logically opposites !) Do [block of statements] Loop While [Condition=True] Do [block of statements] Loop Until [Condition=True]  Syntax: (! logically opposites !) Do [block of statements] Loop While [Condition=True] Do [block of statements] Loop Until [Condition=True]

17/38 Nested loops  Two or more loops in one another: Do Until Error < [statement1] For Count = 1 To 100 [block] Next Count [more statements] Loop  Two or more loops in one another: Do Until Error < [statement1] For Count = 1 To 100 [block] Next Count [more statements] Loop Do not nest in more than 3-4 levels depth

18/38 Dealing with conditions  evaluating a condition: True/False or Cases  branching: 2, 3, 4... N  selection structure:  2 branches (T/F) --> If..Then..Else  3-4 branches --> If..Then..ElseIf..Else  more branches --> Select Case  evaluating a condition: True/False or Cases  branching: 2, 3, 4... N  selection structure:  2 branches (T/F) --> If..Then..Else  3-4 branches --> If..Then..ElseIf..Else  more branches --> Select Case

19/38 If..Then..ElseIf..Then..Else  Syntax: If [Condition=True] Then [block of statements] Else ‘this happens if Condition=False [another block of statements] End If  Syntax: If [Condition=True] Then [block of statements] Else ‘this happens if Condition=False [another block of statements] End If

20/38 If..Then..ElseIf..ElseIf..Then..ElseIf..Else  Syntax: If [Condition1 = True] Then [block of statements] 1 ElseIf [Condition2 = True] Then [block of statements] 2 ElseIf [Condition3 = True] Then [block of statements] 3 Else ‘this happens if all Conditions are False [block of statements] 4 End If  Syntax: If [Condition1 = True] Then [block of statements] 1 ElseIf [Condition2 = True] Then [block of statements] 2 ElseIf [Condition3 = True] Then [block of statements] 3 Else ‘this happens if all Conditions are False [block of statements] 4 End If

21/38 Select Case  Syntax: Select Case [MyVariable] Case [Value1] [block of statements] 1 Case [Value2] [block of statements] 2 … Case [ValueN] [block of statements] N Case Else [else-block of statements] End Select  Syntax: Select Case [MyVariable] Case [Value1] [block of statements] 1 Case [Value2] [block of statements] 2 … Case [ValueN] [block of statements] N Case Else [else-block of statements] End Select

22/38 In one row  in simple cases: If [Condition=True] Then [statement] 1 Else [statement] 2  in simple cases: If [Condition=True] Then [statement] 1 Else [statement] 2

23/38 Nested If  If..Then..(ElseIf..)Else structures can be nested into each other, but consider the extent of this: If [Condition1 = True] Then [block of statements] 1 If [Condition2 = True] Then [block of statements] 2 End If [block of statements] 3 Else [block of statements] 4 End If  If..Then..(ElseIf..)Else structures can be nested into each other, but consider the extent of this: If [Condition1 = True] Then [block of statements] 1 If [Condition2 = True] Then [block of statements] 2 End If [block of statements] 3 Else [block of statements] 4 End If

24/38 Organization of code  Scope (Subs and variables)  Private or Public (Global)  Return value  no return value --> Procedure (Sub)  yes, of a specified type --> Function  Modules and Forms  WorkBook Object > WorkSheet Object  Scope (Subs and variables)  Private or Public (Global)  Return value  no return value --> Procedure (Sub)  yes, of a specified type --> Function  Modules and Forms  WorkBook Object > WorkSheet Object

25/38 ScopeScope  Private  seen within the current Sub  Public (default)  seen within the current Module  Global  only for variables  seen from anywhere  hazard! --> rare  Private  seen within the current Sub  Public (default)  seen within the current Module  Global  only for variables  seen from anywhere  hazard! --> rare

26/38 ProcedureProcedure  no return value (usually)  General form: Public Sub SubName([Arg1], [Arg2]) [statements] End Sub  no return value (usually)  General form: Public Sub SubName([Arg1], [Arg2]) [statements] End Sub

27/38 FunctionFunction  Syntax: Public Function MyFunction(MyArg As Integer) As Integer [statements] End Function  Value: reached under the name MyFunction  e.g. MyFunction = 5 * MyArg  Syntax: Public Function MyFunction(MyArg As Integer) As Integer [statements] End Function  Value: reached under the name MyFunction  e.g. MyFunction = 5 * MyArg

28/38 Handling events  Event Watching in Windows (auto)  Event --> warns all programs running  Handled event: procedure call  e.g. Private Sub Workbook_Activate() … End Sub  Event Watching in Windows (auto)  Event --> warns all programs running  Handled event: procedure call  e.g. Private Sub Workbook_Activate() … End Sub

29/38 File management  open files  read from files  write to files  we will use only text files (txt)  open files  read from files  write to files  we will use only text files (txt)

30/38 File management FileNum = FreeFile ‘Integer, Open ”MyText.txt” As #FileNum Access Read [do something with data] Close #FileNum ‘Never forget!! FileNum = FreeFile ‘Integer, Open ”MyText.txt” As #FileNum Access Read [do something with data] Close #FileNum ‘Never forget!!

31/38 Data output (in xls) Cells(Row,Col)=”Message”

32/38 VB for Excel IDE  Project Explorer  Properties Window  Working area  Immediate Window  ToolBox (on the WorkSheet)  Toolbars: Standard, Debug, Edit, UserForm  Object Browser  Project Explorer  Properties Window  Working area  Immediate Window  ToolBox (on the WorkSheet)  Toolbars: Standard, Debug, Edit, UserForm  Object Browser

33/38 Object Browser  tree structure  functions and parameters  IsNumeric(), Left(), Right(), Mid(), Trim(), CStr(), Cint(), …  return types  to use a function in a branch: MyCosValue = VBA.Math.Cos(MyDoubleVar)... use dots between levels  tree structure  functions and parameters  IsNumeric(), Left(), Right(), Mid(), Trim(), CStr(), Cint(), …  return types  to use a function in a branch: MyCosValue = VBA.Math.Cos(MyDoubleVar)... use dots between levels

34/38 InputBox()InputBox()  Built-in function  Syntax: MyNewValue = InputBox(Prompt, Title, Default) String variableQuestion Def. value  Built-in function  Syntax: MyNewValue = InputBox(Prompt, Title, Default) String variableQuestion Def. value

35/38 Readable code  End of statement: auto  Begin each statement in a new row  e.g. 2 statements in a row: [statement1] : [statement2]  Groups: statments with a similar function  e.g. declarations, output statements, value assignments etc.  Loops: start lines with a Tab inside  End of statement: auto  Begin each statement in a new row  e.g. 2 statements in a row: [statement1] : [statement2]  Groups: statments with a similar function  e.g. declarations, output statements, value assignments etc.  Loops: start lines with a Tab inside

36/38 Literature online You can find the links on our site, just do not forget to do look it up;).  VisualBasic.about.com  MSDN  VB eBook  VBA Tutorial (with example) + The 10 Commandments of VB You can find the links on our site, just do not forget to do look it up;).  VisualBasic.about.com  MSDN  VB eBook  VBA Tutorial (with example) + The 10 Commandments of VB

See you next week:)