Re: [fpc-pascal] implementation-part
On Fri, 15 Dec 2023, Adriaan van Os via fpc-pascal wrote: The Freepascal Language Reference (version 3.2.0) states in section 16.2 "As can be seen from the syntax diagram, a unit always consists of a interface and an implementation part." and "Both the interface part or implementation part can be empty, but the keywords Interface and implementation must be specified. However, this was changed when implementing macpas mode (or at least for the macpas mode) in that the implementation part is no longer obligatory. This is useful for units with (only) external declarations. Really ? Not being a macpas user, I was not aware of this. I will update the documentation. Thank you for pointing it out. Michael. ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
[fpc-pascal] implementation-part
The Freepascal Language Reference (version 3.2.0) states in section 16.2 "As can be seen from the syntax diagram, a unit always consists of a interface and an implementation part." and "Both the interface part or implementation part can be empty, but the keywords Interface and implementation must be specified. However, this was changed when implementing macpas mode (or at least for the macpas mode) in that the implementation part is no longer obligatory. This is useful for units with (only) external declarations. Regards, Adriaan van Os ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] case statement
I have occasionally had ambiguity with ELSE, for example when you have IF statements nested inside other IF statements, sometimes the ELSE is seen as part of the inner, not the outer, or vice versa, depending on where the one-liners are but I just resolve it with some BEGIN - END Blocks, even if they are not actually needed because there is only one line, ambiguity resolved. For years I have just been in the habit of always putting BEGIN and END on all IF and ELSE statements, as well as all entries of CASE statements, whether needed or not, just because it's so much easier to stick in some temporary diagnostic code if needed, it's easier to just always have them and not have to add them later if you want to do a second thing, which always seems to be happening. I guess that's why I never noticed there could be an issue with CASE statements. It is handy to know about OTHERWISE though, I'll probably throw it in just to help remind me that this belongs to the CASE Statement, and not part of some IF, maybe it will be more readable that way. James -Original Message- From: fpc-pascal On Behalf Of Martin Wynne via fpc-pascal Sent: Thursday, December 14, 2023 3:16 PM To: fpc-pascal@lists.freepascal.org Cc: Martin Wynne Subject: Re: [fpc-pascal] case statement I've been using ELSE in IF statements and in CASE statements for 25 years without realising there was a problem. What a dim-wit I have been. Martin. ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] case statement
I've been using ELSE in IF statements and in CASE statements for 25 years without realising there was a problem. What a dim-wit I have been. Martin. ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] case statement
James Richters via fpc-pascal wrote: I didn’t know there was such a thing as OTHERWISE. Is there any functional difference between OTHERWISE and ELSE? No. It is just that OTHERWISE doesn't have the IF-THEN-ELSE ambiguity. Macintosh Pascal compilers had OTHERWISE but not ELSE. Maybe, OTHERWISE was added to FPC when imlementing the macpas mode. Regards, Adriaan van Os ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] case statement
James Richters via fpc-pascal schrieb am Do., 14. Dez. 2023, 20:13: > I didn’t know there was such a thing as OTHERWISE. Is there any > functional difference between OTHERWISE and ELSE? > "otherwise" is what had been defined by ISO Extended Pascal for the cause-statement. Aside from not having the else-problem mentioned in this thread there is no functional difference. Regards, Sven > ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] case statement
I didn’t know there was such a thing as OTHERWISE. Is there any functional difference between OTHERWISE and ELSE? James ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] case statement
Michael Van Canneyt via fpc-pascal wrote:
On Thu, 14 Dec 2023, Adriaan van Os via fpc-pascal wrote:
I am looking in detail at the syntax diagrams in the Freepascal
Language Reference (version 3.2.0)
Section 13.2.2 discusses the case-statement. Translated to EBNF (WSN)
the syntax is
case-statement = "CASE" expression "OF" case { ";" case } [ else-part
] [ ";" ] .
case = constant [ ".." constant ] { "," constant [ ".." constant ] }
":" statement .
else-part = [ "ELSE" | "OTHERWISE" ] statementlist .
If this is correct (and the compiler really allows it) then a
semicolon between and is not required.
It is not required.
In addition to what I wrote, I believe the diagram is also incorrect in that it
doesn't allow an optional semicolon between and .
Regards,
Adriaan van Os
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Re: [fpc-pascal] case statement
On Thu, 14 Dec 2023, Adriaan van Os via fpc-pascal wrote:
I am looking in detail at the syntax diagrams in the Freepascal Language
Reference (version 3.2.0)
Section 13.2.2 discusses the case-statement. Translated to EBNF (WSN) the
syntax is
case-statement = "CASE" expression "OF" case { ";" case } [ else-part ] [ ";"
] .
case = constant [ ".." constant ] { "," constant [ ".." constant ] } ":"
statement .
else-part = [ "ELSE" | "OTHERWISE" ] statementlist .
If this is correct (and the compiler really allows it) then a semicolon
between and is not required.
It is not required.
Consequently, there is an
ambiguity between an if-then-else statement (as last statement of the )
and an if-then statement (as last statement of the ) and an
. This is extremely dangerous and I feel that at least the
Language Reference should warn against it.
A good point. I will add a warning.
Even with an obliged semicolon, I always use "OTHERWISE instead of ELSE, but
that's my personal preference.
Indeed. By contrast I abhorr the OTHERWISE. Tastes differ.
Thanks for bringing the ambiguity to my attention.
Michael.
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Re: [fpc-pascal] case statement
On Thu, Dec 14, 2023 at 5:01 PM Adriaan van Os via fpc-pascal wrote: > I always use "OTHERWISE instead of ELSE, but that's my personal > preference. +1 Seeing OTHERWISE in source code just makes me smile. -- Bart ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
[fpc-pascal] case statement
I am looking in detail at the syntax diagrams in the Freepascal Language
Reference (version 3.2.0)
Section 13.2.2 discusses the case-statement. Translated to EBNF (WSN) the
syntax is
case-statement = "CASE" expression "OF" case { ";" case } [ else-part ] [ ";" ]
.
case = constant [ ".." constant ] { "," constant [ ".." constant ] } ":"
statement .
else-part = [ "ELSE" | "OTHERWISE" ] statementlist .
If this is correct (and the compiler really allows it) then a semicolon between and
is not required. Consequently, there is an ambiguity between an if-then-else statement
(as last statement of the ) and an if-then statement (as last statement of the ) and an
. This is extremely dangerous and I feel that at least the Language Reference should
warn against it.
Even with an obliged semicolon, I always use "OTHERWISE instead of ELSE, but that's my personal
preference.
By the way, the Language Reference doesn't specify what a is.
Regards,
Adriaan van Os
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