Case statement and strings in PAC

Hi all,
I've been writing some code (logic) for serial comms, and ran into a problem with PICED that tells me it can't compile a case statement using a string.
I tried the sample code in the Help file, and it wouldn't work either!

Code:

{var}
Operator: string;
number1: integer;
number2: integer;
result: integer;

case  Operator  of
     '*' : result:= number1 * number2;
     '/' : result:= number1 / number2;
     '+' : result:= number1 + number2;
     '-' : result:= number1 - number2;
end;

and get

Code:

Error C144 at line 592:17 - Illegal type of expression 
    [COLOR="RoyalBlue"]  for line [/COLOR][COLOR="Navy"]case Operator of[/COLOR]

and interestingly

Code:

Error C129 at line 594:38 - Type conflict of operands
    [COLOR="RoyalBlue"]for line [/COLOR][COLOR="Navy"]'/' : result:= number1 / number2;[/COLOR]

I have tried an equivalent code structure where Operator is an integer and there is no problem. Why just with strings and why wouldn't a published example work!
Anyone else run into this? Or am I doing something dumb....

 

Hi Ashleigh. While you are right, changing "operator" the example to a char, rather than a variable does allow it to compile, my issue is with strings, as I am trying to parse the string that comes from the PAC comm port for various (string) commands coming from another device.

 

See the logic help file topic "Serial IO Examples".

 

Actually dividing integers isn't a problem in Pascal (or most languages for that matter). It just gives you a truncated integer result. The problem here is the use of the / operator which is a floating point division operator. For integer division you need the 'div' operator. i.e. result:= number1 div number2;

As for the case statement, as Ashleigh points out, in Pascal the expression can only be of integer or char types (char is actually a byte internally). If you want to use strings you will have to revert back to nested if then else statements.

Alternatively, if you are only interested in a single character in a string, just extract it as an array index (e.g. operator[5] to get the fifth character), which returns a char result and will work in a case statement.

Ashley

 

Thanks guys,
Yes I've been using nested "if"s to get around the problem but its getting a bit cumbersome, not sure if it compiles any cleanly.

Bummer that strings are excluded from a case statement in Pascal. So used to using case in other languages (Basic, C) to parse strings in serial interface code. I haven't written Pascal for 25 years (until now)!

Thaks for the "div", "/" difference. I obviously didn't read the help closely enough.