optional parameter does not kick in

[kryton9]

I have noticed before, but many times by enclosing in () solved it. But here is an example where it doesn't kick in Charles.

Code: OxygenBasic

1. 'optional parameters behaviour
2.  
3. function power( sys number, optional sys exponent = 2 )
4.     return pow( number, exponent )
5. end function
6.  
7. print str( power 2 ) 'the optional parameter does not kick in
8. print str( pow( 2, 4) )
9. print str( power 2, 4 )
10. print str( 2^4 )

[Peter]

Hi Kent,

There is no OPTIONAL!

[Charles Pegge]

Optional parameters and named parameters are two different paradigms

These use named params

Code: OxygenBasic

1. 'named parameters behaviour  
2.  
3. function power( sys number=2, sys exponent = 2 ) as double
4.     return pow( number, exponent )  
5. end function  
6.  
7. print  str power ()
8. print  str power (4, 2)
9. print  str power (exponent=5)
10.  

and these use optional params (which always default to null)

Code: OxygenBasic

1. 'optional parameters behaviour  
2.  
3. function power( optional sys number, exponent ) as double
4.     if  number=0 then number=1
5.     if exponent=0 then exponent=1
6.     return pow( number, exponent )  
7. end function  
8.  
9. print  str power ()
10. print  str power (4)
11. print  str power (4,3)
12.  
13.  

Charles

[Charles Pegge]

Another Oxygen.dll fix. print was giving chinese characters instead of numbers under certain conditions. No need for str ..

Code: OxygenBasic

1.  
2. 'optional parameters behaviour    
3.    
4. function power( optional sys number, exponent ) as double  
5.     if  number=0 then number=1  
6.     if exponent=0 then exponent=1  
7.     return pow( number, exponent )    
8. end function    
9.    
10. print  power ()  
11. print  power (4)  
12. print  power (4,3)  
13.  

Charles

[attachment deleted by admin]

[kryton9]

That is very helpful Charles. Thanks for the nice explanation. I like using optional parameters a lot, now it makes sense that it would check against NULL or 0 then assign what it is needed.

[Charles Pegge]

Here is another example Kent. Using optional parameters passed by reference. In these cases you need to check each address for null.

if  @number=0 then n=2 else n=number

Code: OxygenBasic

1.  
2. 'optional parameters behaviour
3.  
4. 'USING OPTIONAL PARAMETERS BY REFERENCE    
5.    
6. function power( optional sys *number, *exponent ) as double
7.     sys n,e
8.     if  @number=0 then n=2 else n=number  
9.     if @exponent=0 then e=2 else e=exponent
10.     return pow( n, e )    
11. end function    
12.    
13. print  power ()  
14. print  power (4)  
15. print  power (4,3)  
16.  

Charles

[kryton9]

Thanks Charles. Very handy information. As I go back through my class files I will update all of them as I have ConsoleC.inc to work correctly with optional parameters.