IF then question

Just wondering, how would do multiple ifs work in each other?

1 If x = 10
2 While Now = Now
3 Text1.Text = Text1.Text + 1
4 If text1.text = 56 then
5 msgbox "56"
6 end if
7 end if
8 Wend

Will 1 correspond with 6 or 7? will 4 correspond with 6 or 7?
this is what confuses me, this is a really crappy example so ignore it.

Switch the Wend with #7 and End If with #8 ;)

And if you have learned to indent your code, it wouldn't be so confusing:

VB Code:

If x = 10
 
     While Now = Now
          
          Text1.Text = Text1.Text + 1
 
          If text1.text = 56 then
 
              MsgBox "56"
         
          End If
 
     Wend
 
End If

Now you know which one it corresponds with :bigyello:

Quote:

---

Originally Posted by Jacob Roman

Switch the Wend with #7 and End If with #8 ;)

And if you have learned to indent your code, it wouldn't be so confusing:

Now you know which one it corresponds with :bigyello:

---

I agree :thumb:

If you learned some C++, or know a little at least, you would have learned a thing called If Blocks. There is no Then and End If in C++ for if statements. Instead they use curly brackets {} to block in the code that's executed when the condition is true

Code:

---


if(x = 10)
{

//Do stuff here in this block

}

---

So think of the code in between If condition is true Then and End If as an if block without the curly brackets {}.

but, what happeneds if you need to put 2 ifs inside of another if, how does it know which one to go to..does it work like this:


| - if
| | - if
| | | - if
| | | | - if
| | | | - if
| | | - if
| |- if
|- if
?

VB Code:

If x > 10 Then
    If SomeThingElse = False Then
        If YouNeedMoreHelpJustAsk(Someone) = vbYes Then
            'do something
        End If 'end of If YouNeedMore...
    End If 'end of If SomeThingElse
End If 'end of If x

Just look at the indentation. The first If ends at the last line.

You could have IF statements nested like this:
Change values around to see if you can guess what will print.

VB Code:

Option Explicit
 
Private Sub Form_Load()
Dim Condition1 As Boolean
Dim Condition2 As Boolean
Dim Condition3 As Boolean
Dim Condition4 As String
Condition1 = True
Condition2 = True
Condition3 = True
If Condition1 = True Then
  If Condition2 = True Then
    If Condition3 = True Then
      If Condition4 = "Black" Then
        MsgBox "1,2,3,Black"
      Else
        MsgBox "1,2,3,Not Black"
      End If
    Else
      MsgBox "1,not2,not 3"
    End If
  Else
    If Condition3 = True Then
      MsgBox "Not 1, not 2, 3"
    End If
  End If
Else
  MsgBox "Not 4"
End If
End Sub

Hehe, this is getting interesting :bigyello: :

VB Code:

Dim Condition(7) As Boolean
Dim I As Long
 
For I = 0 To 7
 
     Condition(I) = True
 
Next I
 
If Condition(0) = True Then
     
     MsgBox "Condition 0 is True", vbExclamation
 
     If Condition(1) = True Then
 
          MsgBox "Condition 1 is True", vbExclamation
 
          If Condition(2) = True Then
 
               MsgBox "Condition 2 is True", vbExclamation
 
               If Condition(3) = True Then
 
                    MsgBox "Condition 3 is True", vbExclamation
 
                    If Condition(4) = True Then
 
                         MsgBox "Condition 4 is True", vbExclamation
 
                         If Condition(5) = True Then
 
                              MsgBox "Condition 5 is True", vbExclamation
 
                              If Condition(6) = True Then
 
                                   MsgBox "Condition 6 is True", vbExclamation
 
                                   If Condition(7) = True Then
 
                                        MsgBox "It's All True!!!",vbExclamation
                                   
                                   End If 'End Condition 7 Block
        
                              End If 'End Condition 6 Block
 
                          End If 'End Condition 5 Block
                       
                    End If 'End Condition 4 Block  
 
               End If 'End Condition 3 Block     
 
          End If 'End Condition 2 Block
 
     End If 'End Condition 1 Block
 
End If 'End Condition 0 Block

i guess you can see now with Jacob Roman's example you can tell now which is which.

okay i thought it worked like that, but i got super confused and was like *** mate :wave:

I suppose one should use 'end if' in every 'if' for code readability....

How come no one mentions the ElseIf?

VB Code:

If Something = True Then
    MsgBox "Blah"
ElseIf SomethingElse = True Then
    MsgBox "Blah, Blah"
ElseIf SomeOtherThing = True Then
    MsgBox "Blah, Blah, Blah"
Else
    MsgBox "?"
End If

Quote:

---

Originally Posted by dee-u

I suppose one should use 'end if' in every 'if' for code readability....

---

its not for code readability. it is how the language was design there's a term use for that in programming i just can't remember it. Let's just say they're like husband and wife. ;)

...another one i don't see much...

'IIf(expr, truepart, falsepart)

VB Code:

MsgBox IIf(1 = 1, "hello", "goodbye")
        MsgBox IIf(1 = 2, "Bull", 5 * 5)

Ah I think it is called context free grammar.

Quote:

---

its not for code readability. it is how the language was design there's a term use for that in programming i just can't remember it. Let's just say they're like husband and wife.

---

Is that term 'structure'?

Quote:

---

...another one i don't see much...

'IIf(expr, truepart, falsepart)

---

I just use it when I'm saving data to a database, it helps a lot in that area.

whats elseif?

Its just another option in an If Then Else structure.

All these statements are called Decision Structures.

The If Then ElseIf Else End If decision structure is similar to a Select Case decision structure. ;)

What's ElseIf?!!! Ok I'll show ya an example to clear things up. It's pretty obvious if you use common sense ;)

VB Code:

Dim Value As Long
 
Value = (Rnd * 2) + 1 'Any random value within 1 - 3
 
If Value = 1 Then
 
     MsgBox "Value is 1", vbExclamation
 
ElseIf Value = 2 Then
 
     MsgBox "Value is 2", vbExclamation     
 
ElseIf Value = 3 Then
 
     MsgBox "Value is 3", vbExclamation
 
End If

Notice that you didn't need to use End If in there for the ElseIf's. An equivilant to this would be a Select Case statement

VB Code:

Dim Value As Long
 
Value = (Rnd * 2) + 1 'Any random value within 1 - 3
 
Select Case Value
 
     Case 1
 
          MsgBox "Value is 1", vbExclamation
 
     Case 2
 
          MsgBox "Value is 2", vbExclamation     
 
     Case 3
 
          MsgBox "Value is 3", vbExclamation
 
End Select

Quote:

---

Originally Posted by RobDog888

How come no one mentions the ElseIf?

VB Code:

If Something = True Then
    MsgBox "Blah"
ElseIf SomethingElse = True Then
    MsgBox "Blah, Blah"
ElseIf SomeOtherThing = True Then
    MsgBox "Blah, Blah, Blah"
Else
    MsgBox "?"
End If

---

Guess you missed it. :D ;)

:thumb: for completing the example with an Select Case example.

Hehe, thanks. And believe it or not. If you were to make any games to where speed is a must, this first thing I'm about to show you is slightly faster than the other method, although the other method is good for code readability:

Slightly Faster method (No "End If" is needed)

VB Code:

If Condition = True Then MsgBox "Kool"

The other method

VB Code:

If Condition = True Then
 
     MsgBox "Kool"
 
End If

I'm no assembly guru or anything, but something tells me there is less assembly being executed with the single line If Then statement which made it faster.

i didnt miss it, i just wanted an explanation for it. And the select case made me understand it..What are the advantages over select case if there are any?

The Select Case method is good for readability. I heard that it's slightly slower than the If Then ElseIf statements though.

Quote:

---

Originally Posted by Jacob Roman

Slightly Faster method (No "End If" is needed)

VB Code:

If Condition = True Then MsgBox "Kool"

The other method

VB Code:

If Condition = True Then
     MsgBox "Kool"
End If

---

Hmmm.... Are you sure about this Jacob? In my mind the exact same native code should be generated when you compile it, otherwise the VB compiler does a pretty poor job with that.

Anybody up for putting this to a performance test? :D

Quote:

---

Originally Posted by RobDog888

Anybody up for putting this to a performance test? :D

---

OK here a simple test I did:

VB Code:

Private Declare Function GetTickCount Lib "kernel32.dll" () As Long
 
Private Sub OneLineIf()
    Dim n As Long, x As Long
    
    For n = 0 To 1000000
        If x < 1000000 Then x = x + 1
    Next
End Sub
 
Private Sub BlockIf()
    Dim n As Long, x As Long
    
    For n = 0 To 1000000
        If x < 1000000 Then
            x = x + 1
        End If
    Next
End Sub
 
Private Sub Main()
    Dim t As Long
    Dim nOne As Long, nBlock As Long
    
    t = GetTickCount
    OneLineIf
    nOne = GetTickCount - t
    t = GetTickCount
    BlockIf
    nBlock = GetTickCount - t
    MsgBox "Single line If = " & nOne & vbCrLf & "Block If = " & nBlock
End Sub

Not the most perfect performance tester in the world, but I though it would be enough for this.

The result: When running from the IDE the one line If statement was slightly faster but when I run it in compiled form the block was faster some time and the single line others so they tied.

My conclusion: When compiled to native code the same binary code is made, but there is a slight speed advantage with the single line approach if you compile to P-code.

Sure no problem :bigyello:

OMG. That is weird. After running it a few times in IDE mode, the If Then End If was super slow compared to the single line If statement! But in EXE mode I got the complete opposite! What gives :ehh:

VB Code:

'If Value = 1 Then Value2 = 2
        
 
                'Results
                '------------------
                'IDE - 1015072
                'EXE - 1092362
            
            
            If Value = 1 Then
            
                 Value2 = 2
                 
            End If
            
                'Results:
                '-------------------
                'IDE - 439249
                'EXE - 1137829

I only got faster code with the block if some of the times.

Quote:

---

Originally Posted by Jacob Roman

OMG. That is weird. After running it a few times in IDE mode, the If Then End If was super slow compared to the single line If statement! But in EXE mode I got the complete opposite! What gives

---

Probably this:

Quote:

---

Originally Posted by Joacim Andersson

My conclusion: When compiled to native code the same binary code is made, but there is a slight speed advantage with the single line approach if you compile to P-code.

---

JR, did youu use the same code that JA posted for testing?

I got single line slightly faster about 50% of the time in the IDE over 20 runs.
When compiled I got 0 to 0 over 20 runs all using JA's code.
I think my system is too fast to measure the exe test. :D

Edit: I adjusted the loops by * 10 and I got measureable exe results. Turns out
50% of the time they are the same. The rest is 50/50 either way.

Quote:

---

Originally Posted by RobDog888

When compiled I got 0 to 0 over 20 runs all using JA's code.
I think my system is too fast to measure the exe test. :D

---

You have to increase the loop before you compile it. However I think Jacob has a more advanced tester.

great learning thread ! ... now this way doesn't the test show how the comparitive statement impacts the process time...more like real life..??

VB Code:

Sub A2A2()
 
    Dim n As Long
    Dim x As Long
    Dim t1 As Long
    Dim t2 As Long
    Dim t3 As Long
    
    t1 = 0
    t2 = 0
    t3 = 0
 
'SINGLE
    Sleep 1000
    n = 0
    x = 0
'--------------
    t1 = GetTickCount
    For n = 0 To 1000000
        If x < 1000000 Then x = x + 1
    Next
    t1 = GetTickCount - t1
    MsgBox x
'=====================================
 
'BLOCK
    Sleep 1000
    n = 0
    x = 0
'-------------
    t2 = GetTickCount
    For n = 0 To 1000000
        If x < 1000000 Then
            x = x + 1
        End If
    Next
    t2 = GetTickCount - t2
    MsgBox x
'=====================================
    
'SELECT CASE
    Sleep 1000
    n = 0
    x = 0
'-------------
    t3 = GetTickCount
    For n = 0 To 1000000
        Select Case True
            Case x < 1000000
            x = x + 1
        End Select
    Next
    t3 = GetTickCount - t3
    MsgBox x
'=====================================
     
     MsgBox "Single line If = " & t1 & vbCrLf & "Block If = " & t2 & vbCrLf & "Select Case = " & t3
 
End Sub

still trying to pick some meat from these bones...

> i used sleep so each test would begin the same.
> msgbox x for the result.
now the timing approach is limited to ms (the gettickcount thing)
... im thinking a consecutive repetition occurs faster due to microprocessor caching..??...so break it with sleep & msgbox...
...anyway i showed fastest is one liner, select case last...and i also tested IIF ...wicked slow...:)

I heard that the Select Case method is slightly slower than ElseIf. Might as well test it to make sure ;)

I knew the single line IF statement was faster :bigyello:

Try it on EXE mode to make sure though.

...consistantly....

Single line If = 47
Block If = 63
Select Case = 94
ElseIf = 78
IIF = 281