Re: SDL-News: Integer to Time casting

Subject: Re: SDL-News: Integer to Time casting
From: Rick Reed TSE (rickreed#tseng.co.uk)
Date: Tue Jul 29 2003 - 11:14:51 GMT

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-----From Rick Reed TSE <rickreed#tseng.co.uk> to sdlnews -----

Margarita de Cabo Pérez at marcab#yllera.tel.uva.es wrote on 25/07/2003
19:06:

> Hi,
>
> I would like to transform an integer value into a Duration value, and
> viceversa. I understand
> that Duration is in fact a real type, but I can put my integer into a real
> an
> used the last like Duration. I doing the following:
>
> dcl tiempoQueda Duration;
> dcl tiempo Integer;
>
> tiempo:=fix(tiempoQueda);
> What I have to do?
> I'm working with Cinderella.
>
> Marga

Dear Marga,

Multiply is defined for Duration:

"*" (Duration, Real) -> Duration;
"*" (Real, Duration) -> Duration;

and float is defined for Real

float(Integer) -> Real;

so you should be able to write

tiempoQueda := 1*float(tiempo)

or

tiempoQueda := float(tiempo)*1;

I have not tried this and you may need some qualifiers such as

tiempoQueda := <<TYPE Real>>float(tiempo)*<<TYPE Duration>>1;

to make sure the expression is unambiguous.

This converts an the integer value into a Duration value.

Fix is not defined for Duration so

fix(tiempoQueda)

is not a valid expression, so your assignment above is not correct.

It seems to me this is an oversight.
SDL could be extended with

fix(Duration) -> Integer;
float(Duration) -> Real;

although

real(Duration) -> Real;

would be just as useful.

With the current language definition, you would have to write an algorithm
to find the appropriate Integer value. For example,

PROCEDURE fixDuration( d Duration) -> Integer;
{ DCL negative Boolean := false;
  DCL i Integer := 0;
  IF (d < 0) { negative := true; d := -d;};
  LOOP (i, <<TYPE duration>>1*(i+1) < d , i + 1 );
  IF (negative) i := -i;
  RETURN i;
}

But obviously if the actual durations are more than just a few units this
would be quite inefficient.

tiempo:=CALL fixDuration(tiempoQueda);

should then do the conversion (If I got the algorithm right -- I have not
check the grammar or the logic). 

--
Rick Reed - rickreed#tseng.co.uk
Tel:+44 15394 88462 Mob.:+44 7970 50 96 50

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