non local variables in Oberon-07

[nojb]

Hello,

Am I understanding correctly the Oberon-07 report when it says that it
doesn't
allow non-local variables in the body of nested procedures? (page 11,
line -2).

Thanks!
N

[Chris Burrows]

Post by nojb
Hello,
Am I understanding correctly the Oberon-07 report when it says that it
doesn't
allow non-local variables in the body of nested procedures? (page 11,
line -2).
Thanks!
N

In an Oberon-07 procedure you can only access global variables or *strictly
local* variables. For example:

MODULE M;

VAR
v, w: INTEGER;

PROCEDURE P;
VAR v: INTEGER;

PROCEDURE NestP1;
BEGIN
v := 999 (* error: non-local is not accessible *)
END NestP1;

PROCEDURE NestP2;
VAR v: INTEGER;
BEGIN
v := 999 (* the local v is modified *)
END NestP2;

PROCEDURE NestP3;
BEGIN
w := 999 (* the global w is modified *)
END NestP3;

END P;

END M.

This helps to prevent some maintenance / obscure runtime problems. For
example, if the local v is introduced in P sometime after the original
program was written, the fact that it now hides the global v from NestP1 is
made obvious to the programmer.

Regards,
Chris Burrows

Astrobe: ARM Oberon-07 Development System
http://www.astrobe.com