Programming > Bugs & Feature Requests

Removal of C-style Ternary

(1/1)

Charles Pegge:
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: ---macro iif int(r, a ,b, c)
  if a
    r=b
  else
    r=c
  endif
end macro

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


--- End code ---

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

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

Charles Pegge:

--- Code: ---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

--- End code ---

Nicola:
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 ---use consolecls 'macro iif int(r, a ,b, c)macro iif int(r, x ,y, z)  if x    r=y  else    r=z  endifend macro '==main==========int a=5, b=6, c=7, d=9 int t=iif(a>b , c, d)print twait
In this case, rightly so, the result is 9.

JRS:
Are macros like user defined syntax extensions?

How are macros unlike functions?


--- Code: Script BASIC ---'IIF Function FUNCTION IIF(x, y, z)  IF x THEN    IIF = y  ELSE    IIF = z  END IFEND FUNCTION  SPLIT "5,6,7,9" BY "," TO  a, b, c, d PRINT IIF(a > b, c, d), "\n" 

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

C:\ScriptBASIC\examples>

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