[Oberon] How to write this program in Oberon-07?

[August Karlstrom]

As mentioned by Jörg, Oberon-07 is a pure structured language in the 
sense that each (ASSERT free) statement sequence is either fully 
executed or not executed. With CASE statements you can often limit the 
range of values to inspect before the CASE statement is executed. Here 
is one way to do it:

MODULE case;

	IMPORT In, Out;

	VAR
		countVowels: INTEGER;
		ch, capCh: CHAR;

BEGIN
	In.Open;
	countVowels := 0;
	In.Char(ch);
	WHILE In.Done DO
		IF (ch >= "a") & (ch <= "z") THEN
			capCh := CHR(ORD("A") + ORD(ch) - ORD("a"))
		ELSE
			capCh := ch
		END;
		IF (capCh >= "A") & (capCh <= "U") THEN
			CASE capCh OF
				"A", "E","I","O","U":
					INC(countVowels) |
				"B", "C", "D", "F", "G", "H", "J", "K", "L", "M", "N", "P", "Q", 
"R", "S", "T":
					(*do nothing*)
			END
		END;
		In.Char(ch)
	END;
	Out.Int(countVowels, 0);
	Out.String(" vowels read.");
	Out.Ln
END case.

With the WHILE loop we can see instantly that it will continue until 
there are no more characters to read. Compare this to the LOOP in which 
the exit condition (or possibly exit conditions) is buried in the 
contained statement sequence.


-- August


On 2022-01-24 15:14, Joe Turner wrote:
> I'm working through the book "Into the Realm of Oberon" which is written 
> for Oberon-2. I can't figure out how to translate the following program 
> into Oberon-07 (I'm using the OBNC compiler):
> 
> MODULE case;
> IMPORT In,Out;
> 
> VAR countVowels: INTEGER; ch: CHAR;
> 
> BEGIN
>    In.Open;
>    countVowels:=0;
>    LOOP
>      In.Char(ch);
>      IF ~In.Done THEN EXIT END;
>      CASE ch OF
>        "a", "e", "i", "o", "u",
>        "A", "E","I","O","U": INC(countVowels)
>      ELSE
>      END;
>    END;
>    Out.Int(countVowels,0);
>    Out.String(" vowels read.");Out.Ln;
> END case.
> 
> Oberon-07 doesn't allow LOOP, EXIT, or ELSE in CASE.
> Thanks in advance for any help.
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> 
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