Recursive function

S

Shining

Member
Licensed User
Longtime User
Hi There,

I have a problem with a simple recursive function.
It works only for number <= 21.
When I debug I see the correct value getting returned but it seems that he also returns null for the first stacked function-call.
Maybe I'm overlooking something obvious ?

Sub CalculateSoul(p_datum)
For t = 0 To StrLength(p_datum)-1
l_nr = l_nr + SubString(p_datum,t,1)
Next
If l_nr <= 21 Then
Return l_nr
Else
CalculateSoul(l_nr)
End If
End Sub
 
S

sitajony

Active Member
Licensed User
Hi, did you try with StrAt()?
B4X: 
[FONT=Courier New][SIZE=2][COLOR=#0000ff][FONT=Courier New][SIZE=2][COLOR=#0000ff][FONT=Courier New][SIZE=2][COLOR=#0000ff]Sub [/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][FONT=Courier New][SIZE=2][FONT=Courier New][SIZE=2]CalculateSoul(p_datum) [/SIZE][/FONT]
[/SIZE][/FONT][FONT=Courier New][SIZE=2][COLOR=#0000ff][FONT=Courier New][SIZE=2][COLOR=#0000ff][FONT=Courier New][SIZE=2][COLOR=#0000ff]For[/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][FONT=Courier New][SIZE=2][FONT=Courier New][SIZE=2] t = [/SIZE][/FONT][/SIZE][/FONT][FONT=Courier New][SIZE=2][COLOR=#800080][FONT=Courier New][SIZE=2][COLOR=#800080][FONT=Courier New][SIZE=2][COLOR=#800080]0 [/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][FONT=Courier New][SIZE=2][COLOR=#0000ff][FONT=Courier New][SIZE=2][COLOR=#0000ff][FONT=Courier New][SIZE=2][COLOR=#0000ff]To [/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][FONT=Courier New][SIZE=2][COLOR=#0000ff][FONT=Courier New][SIZE=2][COLOR=#0000ff][FONT=Courier New][SIZE=2][COLOR=#0000ff]StrLength[/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][FONT=Courier New][SIZE=2][FONT=Courier New][SIZE=2](p_datum)-[/SIZE][/FONT][/SIZE][/FONT][FONT=Courier New][SIZE=2][COLOR=#800080][FONT=Courier New][SIZE=2][COLOR=#800080][FONT=Courier New][SIZE=2][COLOR=#800080]1[/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT]
[SIZE=2][FONT=Courier New][SIZE=2][FONT=Courier New]l_nr = l_nr + [/FONT][/SIZE][/FONT][/SIZE][FONT=Courier New][SIZE=2][COLOR=#0000ff][FONT=Courier New][SIZE=2][COLOR=#0000ff][FONT=Courier New][SIZE=2][COLOR=#0000ff]StrAt[/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][FONT=Courier New][SIZE=2][FONT=Courier New][SIZE=2](p_datum,t) [/SIZE][/FONT]
[/SIZE][/FONT][FONT=Courier New][SIZE=2][COLOR=#0000ff][FONT=Courier New][SIZE=2][COLOR=#0000ff][FONT=Courier New][SIZE=2][COLOR=#0000ff]Next[/COLOR][/SIZE][/FONT]
[/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][FONT=Courier New][SIZE=2][COLOR=#0000ff][FONT=Courier New][SIZE=2][COLOR=#0000ff][FONT=Courier New][SIZE=2][COLOR=#0000ff]If[/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][FONT=Courier New][SIZE=2][FONT=Courier New][SIZE=2] l_nr <= [/SIZE][/FONT][/SIZE][/FONT][FONT=Courier New][SIZE=2][COLOR=#800080][FONT=Courier New][SIZE=2][COLOR=#800080][FONT=Courier New][SIZE=2][COLOR=#800080]21 [/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][FONT=Courier New][SIZE=2][COLOR=#0000ff][FONT=Courier New][SIZE=2][COLOR=#0000ff][FONT=Courier New][SIZE=2][COLOR=#0000ff]Then[/COLOR][/SIZE][/FONT]
[/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][FONT=Courier New][SIZE=2][COLOR=#0000ff][FONT=Courier New][SIZE=2][COLOR=#0000ff][FONT=Courier New][SIZE=2][COLOR=#0000ff]Return[/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][FONT=Courier New][SIZE=2][FONT=Courier New][SIZE=2] l_nr [/SIZE][/FONT]
[/SIZE][/FONT][FONT=Courier New][SIZE=2][COLOR=#0000ff][FONT=Courier New][SIZE=2][COLOR=#0000ff][FONT=Courier New][SIZE=2][COLOR=#0000ff]Else[/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT]
[SIZE=2][FONT=Courier New][SIZE=2][FONT=Courier New]CalculateSoul(l_nr) [/FONT][/SIZE]
[/FONT][/SIZE][FONT=Courier New][SIZE=2][COLOR=#0000ff][FONT=Courier New][SIZE=2][COLOR=#0000ff][FONT=Courier New][SIZE=2][COLOR=#0000ff]End [/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][FONT=Courier New][SIZE=2][COLOR=#0000ff][FONT=Courier New][SIZE=2][COLOR=#0000ff][FONT=Courier New][SIZE=2][COLOR=#0000ff]If[/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT]
[FONT=Courier New][SIZE=2][COLOR=#0000ff][FONT=Courier New][SIZE=2][COLOR=#0000ff][FONT=Courier New][SIZE=2][COLOR=#0000ff]End Sub[/COLOR][/SIZE][/FONT]
[/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT]
I've a question:
Why search each characteres if it's a number and who is the same that p_datum?
Maybe you want add others code after... (Sorry for this bad question)

Anyway:
If your code is really the same, it'll loop infinitly if the number is less than 22...

Big Edit:
I'm stupid, I've not saw "-1" in StrLength() sorry...
 
Last edited:
S

Shining

Member
Licensed User
Longtime User
Hi there,
The purpose is to add every digit of a "string" with only numeric characters together.
The result will be returned by the function if it is less then 22.

So for p_datum= "13011970" = 1+3+0+1+1+9+7+0 = 22

So it will run the function agein with 22. 2+2=4, so now it will return 4.

This works when I debug, I get the value 4 which is in the return value, but then I think it returns from the previous call where the value is 22, there it returns nothing so the end result is null.

So the problem is that I loose the returning value, probably due to invalid logic in my code ?
 
P

Pachuquin

Member
Licensed User
Longtime User
I speak English very bad, but I will try to explain it.

The problem is that you have to return a value each time you call CalculateSoul.

B4X: 
Sub CalculateSoul(p_datum)

For t = 0 To StrLength(p_datum)-1 
   l_nr = l_nr + SubString(p_datum,t,1) 
Next  t

If l_nr <= 21 Then

   result= l_nr
Else 
   result=CalculateSoul(l_nr)

End If 
   Return result
End Sub

Try this
 
S

Shining

Member
Licensed User
Longtime User
Hi Pachuquin,
Thanks a lot...your're so right.
I forgot to return the value in my recursive call, like you said.
I changed my code to the one you see here, and the result is ok.

B4X: 
Sub CalculateSoul(p_datum)       
  For t = 0 To StrLength(p_datum)-1    
   l_nr = l_nr + SubString(p_datum,t,1)    
  Next     
  If l_nr <= 21 Then
     Return l_nr    
  Else    
    Return CalculateSoul(l_nr)   
  End If  
End Sub
 
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