Re: Use of { and } was Re: Back & Forth - Co-routines

On 6/02/2025 12:38 pm, Waldek Hebisch wrote:

Anton Ertl <anton@mips.complang.tuwien.ac.at> wrote:

dxf <dxforth@gmail.com> writes:

On 1/02/2025 11:14 pm, albert@spenarnc.xs4all.nl wrote:

{ } is used for comment in Pascal.

>
That's interesting.  When did that come in, and why, given the issues?

>
Good question.  My memory is only of (* *), but indeed Section 6.1.8
of https://www.standardpascal.org/iso7185.pdf makes it clear that (*
and { can be used interchangeably, as well as *) and }.

 
'{' and '}' are original Pascal comments.  I do not think they have
any issue beyond normal ones, that is inability to put '}' as
part of a comment.  Since comments were intended to be text and
'}' is not used as normal part of text presumably inability to
put '}' inside a comment was deemed as non-issue.
 
Pascal was bases on ASCII, but IBM mainframes used EBCDIC which
missed several useful ASCII characters, notably '{', '}',
'[', '[', so Pascal implementations on IBM mainframes used
alternate sequences.  The alternative seqences were standarized
together with originals.
 
More generally, Wirth had rather rigid view how "good" program
should look like and this view was enforced by Pascal compilers.
Practical Pascals and later Extended Pascal were much more
flexible.

From Wirth's own examples it appears { } was used much like forth uses
( ) or \  i.e. as an inline code comment.  Getting back to FI, its choice
of { } as a general block comment seems particularly ill-considered given
( ) \ already existed.  Unlike Pascal { } was never intended as an inline
code comment.