Re: Parsing CL comments

[Charles Wilt <charles.wilt@xxxxxxxxx>]

Starting with this (from http://en.wikipedia.org/wiki/AS/400_Control_Language):
<CL-command> ::= command-name [<positional-parameter-list>]
[<named-parameter-list>]

<positional-parameter-list> ::= <parameter-value> [<positional-pararmeter-list>]

<named-parameter-list> ::= parameter-name"(" <parameter-element-list>
")" [<named-parameter-list>]

<parameter-element-list> ::= <parameter-value> [<parameter-element-list>]

<parameter-value> ::= CL-name |
                      qualified-CL-name |
                      "*"special-value |
                      generic-CL-name"*" |
                      "'"alphanumeric-value"'" |
                      numeric-value |
                      "X'"hexadecimal-value"'"

let's add:

<qualified-CL-name> ::= CL-name"/"CL-name |
                                    CL-name"/""*"special-value



The parser knows that MYLIB/*ALL and PART2/*PART1 are of type
<parameter-value>.  More specifically, the parser knows they are
<qualified-CL-name> using a *special-value.

So the parser isn't isn't going to consider it possible they could be comments.

if you where to try and put a comment in the middle of a
<parameter-value> you'd get a syntax error, which simply means the
parser didn't find something it expected or found something it didn't.

Lastly, consider the following from the manual:
"Comments can be inserted either inside or outside a command’s
character string wherever a blank is permitted. However, because a
continuation character must be the last non-blank character of a line
(or record), comments may not follow a continuation character on the
same line.
Comments can include any of the 256 EBCDIC characters. However, the
character combination */ should not appear within a comment because
these characters end the comment. To begin a comment, the characters
/* must be placed in the first position of the command, be preceded by
a blank, or be followed by either a blank or an asterisk."

This is allowed
/*Comment With no space*/
DSPLIBL OUTPUT(*PRINT)  /*Comment with no space*/

 This is not
DSPLIBL OUTPUT(*PRINT)/*Comment with no space*/

HTH,
Charles
On Tue, Dec 15, 2009 at 12:31 PM, Dennis Lovelady <iseries@xxxxxxxxxxxx> wrote:
> > I'm not an expert ( it's been a while since my formal languages course
> > :) but recursive decent parsing provides an answer to your OQ in the
> > following manner:
> >
> > At the point that the parser is looking at /*ALL or /*PART1 the parser
> > wouldn't be looking for a comment.
>
> Thanks, Charles.  You see something that I don't.  With what we know, what
> would prevent the parser from looking for a comment there?  I look at this
> and say, Is a blank allowed here?  Yes, so a comment may appear here.
> Right?  What am I missing?
>
> Dennis Lovelady
> http://www.linkedin.com/in/dennislovelady
> --
> "Most people spend their lives going to bed when they're not sleepy and
> getting up when they are."
>        -- Cindy Adams
>
>
>
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