Re: [GNU-COBOL] instant top-level parser

[Randall Bart <Barticus@att.net>]

At 03:04 PM 10/29/99 , David L. Nicol wrote:
>Randall Bart wrote:
> > COBOL-20XX has done away with margin B, so all recognition of headers is
> > driven on separator-periods alone.  The ZIF should be parsed into a next
> > intermediate form (NIF)  period delimited sentences.  Then the next
> > intermediate form is to parse this into programs, divisions, sections, and
> > paragraphs.  This form would identify the nesting of programs so we call
> > this the nested intermediate form (NIF).
>
>"separator periods" are periods followed by whitespace,

Yes.

>except
>for single periods in PIC clauses which can be replaced with Vs by
>the programmer for identical functionality, correct? So the first
>period on a line after the letters PIC can be changed into a V?

No.  Picture characters period and V aren't interchangeable.  Both specify 
the location of the decimal point, but V doesn't occupy storage while 
period does.

>Question -- Were separator periods optional in the
>margin B days, or was the blocking redundant that way?

The syntax was redundant.  The standard said that headers start in Margin 
A, and everything else started in margin B, but inherently whatever comes 
before the header ends with a separator period.  Users preferred not to 
worry about the margins, so some implementors relaxed the margin 
requirements.  It causes some invalid syntax to generate non-intuitive 
error messages, but valid syntax is always parseable this way.

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