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From: sml@ssc-vax (Stuart Lewis)
Newsgroups: comp.lang.pascal
Subject: Re: Third TPascal
Keywords: puzzle,pascal
Message-ID: <4223@ssc-bee.ssc-vax.UUCP>
Date: 28 Jun 91 18:19:02 GMT
References: <1991Jun27.131018.26430@informatik.uni-erlangen.de>
Sender: news@ssc-vax.UUCP
Reply-To: sml@ssc-vax.UUCP (Stuart Lewis)
Organization: Boeing Aerospace & Electronics
Lines: 123

In article <1991Jun27.131018.26430@informatik.uni-erlangen.de> prknoerr@immd4.informatik.uni-erlangen.de (Peter Knoerrich) writes:
>Ok, here you are, the third one:
>
>This one needs some warnings, for it will for sure not run on
>any compiler. For instance, you need a word data type which
>is not implemented on most unix pc compilers (for some good
>reason, agreed). 
>
>But I think most of you guys either use Borland's TurboPascal 
>or perhaps some other pascal which does have unsigned data types, 
>so you will perhaps be able to follow this one (I know I'm 
>advertising, but at least it's for a reasonable product I do it for)
>

I'm not sure I understand what you're telling me here about the word
data type.  But then, I program on the VAX - not on pc's (not until
this fall anyway).  Given that forewarning about my lack of pc
Pascal, let me approach your code from a standard VAX Pascal point of
view.......

>program AdjustValue;
>

(* the var declaration must be here - not after the procedure *)
(* that *immediately* will give compile time errors *)

VAR (* from below *)
  given : word; (* from below *)

>procedure AdjustAndTrim(var value : word;change : integer);
				       (* ^^^^^^ since "change" is
				       always -1, it would be
				       'tidier' to declare it as a
				       constant up above and not
				       worry about passing it *)
>  var
>    temp : integer;
>  begin
>    temp := value + change;

(* I don't know what TYPE "word" is (pc exclusive?), but this last
line will not work unless "value" (VAR'd "given") is ultimately
either an INTEGER value or CHAR value, because "temp" is declared as
type INTEGER.  You can declare a data type word = INTEGER; up above
your global VAR's, and then it would work. *)

>    if (temp<0) then 
>      temp := 0
>    else
>      if (temp>1000) then
>        temp := 1000;
>    value := temp;
>  end;
>
>var (* global VAR - delete this line - move to above *)
>  given : word (* ditto - plus syntax error, need ";" at end *)
>
>begin
>  given := 0;

(* here again, I don't know what type "word" is, but you're
assigning an INTEGER (or possibly CHAR) value to "given" - save
yourself some trouble and declare it as one of those two *)

>  AdjustAndTrim(given,-1);
>end.
>
[stuff deleted]
>
>What goes wrong is the following: Even the first assignment fails.
>Though an integer has been provided to catch up with those negative
>fellows, a range check error will occur when called with the given
>parameters.
>
[stuff deleted]
just a matter of personal preference or style, but here's what I
would do....

PROGRAM AdjustValue (input, output);

   CONST
      change = -1;

   TYPE
      word = INTEGER;

   VAR
      given : word;

	PROCEDURE AdjustAndTrim (VAR value : word);

	   VAR
	      temp : INTEGER;

	   BEGIN (* PROCEDURE AdjustAndTrim *)
	      temp := value + change;
	      IF (temp < 0) THEN
		 value := 0
	      ELSE IF (temp > 1000) THEN
		 value := 1000
	      ELSE
		 value := temp;
	   END; (* PROCEDURE AdjustAndTrim *)
   
   BEGIN (* MAIN *)
      write('Enter a value : ');
      readln(given);
      AdjustAndTrim(given);
      writeln('Adjusted value is : ', given);
   END. (* MAIN *)

I added read & write statements - the program isn't very useful as a
learning tool unless you can see what the heck it's doing! :-)
Again, this is just my personal style, but it does solve the TYPE
problems with "word" and "given".  I didn't run this, but I'd be
*real* embarassed if it crashed on somebody!

>---
>sig? You must be kidding with all those SIGKILLs around on this machine!
>Peter Knoerrich,        email: prknoerr@faui43.informatik.uni-erlangen.de

Stuart Lewis
sml@ssc-vax