Oxygen Basic

Programming => Bugs & Feature Requests => Topic started by: Charles Pegge on August 22, 2020, 05:28:53 AM

Title: Removal of C-style Ternary
Post by: Charles Pegge on August 22, 2020, 05:28:53 AM

O2 will no longer support C expressions like:

r=(a>b ? c : d)

This is an expensive construction to check for during compilation.

Basic ternary expressions are easily implemented using a macro:

Code: [Select]

macro iif int(r, a ,b, c)
  if a
    r=b
  else
    r=c
  endif
end macro

r=iif(a>b , c, d)


correction: r=iif(a>b , c, d)

Title: Re: Removal of C-style Ternary
Post by: Nicola on September 14, 2020, 06:08:11 AM

Please explain to me how this macro works?
thank you :-[

Title: Re: Removal of C-style Ternary
Post by: Charles Pegge on September 14, 2020, 07:20:18 AM

Code: [Select]

macro iif int(r, a ,b, c)
'int indicates the type of temp variable r
'r will replace the macro invoked in an expression
'the macro is executed beforehand to resolve the value of r
'a is a boolean / comparative expression
'b and c are return values for r
  if a
    r=b
  else
    r=c
  endif
end macro

r=iif(a>b , c, d)

'expands to:

'int temp_r
'if a>b
'  temp_r=c
'else
' temp_r=d
'endif
'...
'r=temp_r


Title: Re: Removal of C-style Ternary
Post by: Nicola on September 18, 2020, 02:53:36 PM

Ok Charles.
For me it is clearer in this way, using variables with different names, because I can better identify which are the variable parameters and which are part of the macro and which depend on the values ​​passed through the call of the macro itself. In our case iif ...
Still, a really good thing. Good job.

Code: OxygenBasic

1. use console
2. cls
3.  
4. 'macro iif int(r, a ,b, c)
5. macro iif int(r, x ,y, z)
6.   if x
7.     r=y
8.   else
9.     r=z
10.   endif
11. end macro
12.  
13. '==main==========
14. int a=5, b=6, c=7, d=9
15.  
16. int t=iif(a>b , c, d)
17. print t
18. wait

In this case, rightly so, the result is 9.

Title: Re: Removal of C-style Ternary
Post by: JRS on September 18, 2020, 03:33:37 PM

Are macros like user defined syntax extensions?

How are macros unlike functions?

Code: Script BASIC

1. 'IIF Function
2.  
3. FUNCTION IIF(x, y, z)
4.   IF x THEN
5.     IIF = y
6.   ELSE
7.     IIF = z
8.   END IF
9. END FUNCTION
10.  
11.  
12. SPLIT "5,6,7,9" BY "," TO  a, b, c, d
13.  
14. PRINT IIF(a > b, c, d), "\n"
15.  

C:\ScriptBASIC\examples>sbc iif.sb
9

C:\ScriptBASIC\examples>