case statment

ta5

Hi

There is a special possibility with case statement

CASE TRUE OF
  Expression1:; //do something
  Expression2:; //do something
  ELSE //do something
END;

Personally I think a construction like this is a bit easier to read than subsequent if or else if statements. What is your opinion?
Regards
Thomas

einsTeIn.NET

I know this possibility for a long time. The problem I have with it is that it'll only execute the first condition that matches. If there are more conditions that are true it won't execute the code of it.

lvanvugt

ta5 wrote:

Personally I think a construction like this is a bit easier to read than subsequent if or else if statements. What is your opinion?

Agree

einsTeIn.NET wrote:

... it'll only execute the first condition that matches ...

This is also the case with if ... else (if)

einsTeIn.NET

If we are talking about nested IF statements that's true. But how would you replace nested IF statements with the construction above?

ta5

einsTeIn.NET wrote:

problem I have with it is that it'll only execute the first condition that matches. If there are more conditions that are true it won't execute the code of it.

That's why I like it

einsTeIn.NET

My personal feeling is that it would be better if you could decide if you want to leave the case statement or not. Like in other programming languages where you explicitly need to set a break statement.

vaprog

The above CASE statement is functionally the same as (more conditions added)

IF Expression1 THEN BEGIN
  ; //do something
END ELSE IF Expression2 THEN BEGIN
  ; //do something
...
END ELSE IF Expression_n THEN BEGIN
  ; //do something
END ELSE BEGIN
  //do something
END;

Which is just my way of writing a series of IF statements where each else consists of exactly one IF THEN ELSE statement.

IF Expression1 THEN BEGIN
  ; //do something
END ELSE 
  IF Expression2 THEN BEGIN
    ; //do something
  END ELSE
...
                  IF Expression_n THEN BEGIN
                    ; //do something
                  END ELSE BEGIN
                    //do something
                  END;

Many modern languages actually have an IF ... THEN ... ELSIF ... ELSE statement which my code layout mimics and is more readable than the nested IFs, as is the CASE TRUE OF. The latter is less familiar to many programmers, and especially those coming from C and languages with a switch statement patterned after C tend to have problems remembering:

• The first, and only the first matching section is executed.
• There is no fall-trough, so subsequent sections are out of reach, no break needed.

The nested IF .. ELSE IF sequence is free from both and thus more easily readable.

ta5

Thanks for your contributions, very welcome. I've set the topic to solved.
Regards
Thomas

rocatis

ta5 wrote:

Personally I think a construction like this is a bit easier to read than subsequent if or else if statements. What is your opinion?

I use the CASE TRUE OF extensively. I find the alternative (IF THEN ELSE IF THEN...) completely unreadable.