Re: [BLACKBOX] Modula-2 LineDrawing source?

From: [at]} <CFB>
Date: Sun, 9 Mar 2008 13:31:03 +1030

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> -----Original Message-----
> From: BlackBox [mailto:BLACKBOX{([at]})nowhere.xy
> Bob Walkden
> Sent: Saturday, 8 March 2008 8:35 PM
> To: BLACKBOX{([at]})nowhere.xy
> Subject: [BLACKBOX] Modula-2 LineDrawing source?
>
> Hi,
>
> does anyone know where I can get a copy of the source code of the
> LineDrawing implementation module, as described in Prof. Wirth's
> 'Programming in Modula-2' and 'Algorithms and Data Structures'?
>
> I'd like to see how the line procedure is implemented. The interface
> from the definition module is:
>
> PROCEDURE line( d, n: INTEGER );
> (* draw a line of length n in direction d (angle = 45*d degrees ) *).
>

The following (*untested by me *) is from an implementation of Modula-2 for
the Amiga

http://aminet.net/package/dev/m2/Turbo_Part1

http://aminet.net/package/dev/m2/Turbo_Part2

(NOTE: The comment is not mine - it was in the original):

(* ***********************************************************************
*)
(* A really *sad* line drawing procedure by N. Wirth.
*)
(* ***********************************************************************
*)

VAR
  Px, Py : REAL; (* Stuff needed by line(). *)

PROCEDURE rad(deg: INTEGER): REAL;
CONST
  pi = 3.14159265;
BEGIN
  RETURN FLOAT(deg)*pi/180.0;
END rad;

PROCEDURE line(d, n: INTEGER);
(* draw a line of length n in direction d (angle = 45*d degrees) *)
VAR
  fd, fn : REAL;
  oldx, oldy : REAL;
BEGIN
  fd := rad(45*d+90);
  fn := FLOAT(n);
  oldx := Px;
  oldy := Py;
  Px := oldx + fn * MathIEEESingTrans.IEEESPCos(fd);
  Py := oldy - fn * MathIEEESingTrans.IEEESPSin(fd);
  DrawLine(TRUNC(oldx), TRUNC(oldy), TRUNC(Px), TRUNC(Py));
END line;

> I've googled till my fingers bleed (almost), but can't find it.
>

Next time do what guitarists do and soak your fingers in vinegar ;-)

Regards,
Chris

Chris Burrows
CFB Software
http://www.cfbsoftware.com/modula2

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Received on Sun Mar 09 2008 - 04:01:03 UTC