[Oberon] RISC emulator and floating-point

[Jan Verhoeven]

Paul Onyschuk wrote:
>    PROCEDURE WriteInt* (VAR W: Writer; x, n: LONGINT);
>      VAR i: INTEGER; x0: LONGINT;
>        a: ARRAY 10 OF CHAR;
>    BEGIN i := 0;
> (* Taking this branch, since x = 80000000H = -2147483648 *)
>      IF x < 0 THEN
>        IF x = 0 THEN WriteString(W, " -2147483648")


This is a nonsense statement. If x < 0, it will never be equal to 0. The 
second IF branch is never executed.


>      REPEAT
>        a[i] := CHR(x0 MOD 10 + 30H); x0 := x0 DIV 10; INC(i)
> (* Loop never terminates, since -1 DIV 10 = -1 and x0 is never 0 *)
>      UNTIL x0 = 0;


Normally you would make sure the dividend is > 0. To do this, you make a 
conditional like

IF  x < 0  THEN  sign := -1; x = -x  ELSE  sign := 1  END;

Do the normal conversion (which WILL terminate) and afterwards just do

q := q * sign

and you're done.


-- 
Groetjes

Jan Verhoeven