Re: Daren Scot Wilson's problem

[Valeriy E. Ushakov]

On Sun, May 09, 1999 at 05:06:33PM -0600, Tamas Papp wrote:

> > @Document 
> >   @PageHeaders {Simple}
> > //
> > @Text @Begin
> > 
> > As the User's Guide says, the world will end if you leave // out.
> > Stupid I know, but there it is.
> 
> Could you please explain why we need it, ie what's the significance
> of it?  From the User's Guide I know when to use it, but it's still
> a bit like magic :)

It's buried in the docs, but it's documented somewhere that Lout
breaks ouptut into PostScript pages at the outermost vertical
concatenation points:

    @ObjectOne // @ObjectTwo // @ObjectThree // ...

will have @ObjectOne as the first page of PostScript output,
@ObjectTwo as the second and so on.


@Document and its cousins provide a list of pages of appropriate size
that receives the body of the document.  However when you write

    @Document @Text {}

there's an implicit paragraph (&-concatenation), i.e.:

    @Document & @Text {}

and the //-concatenation of pages is no longer at the outermost level.
So you need to put a // after the document so that the list of pages
that the @Document expands into is at the top level.


The contents of the @Text galley will eventually be transferred into
the receiptive symbols inside the @Document and the @Text at the point
of it's invocation will be replaced by @Null.  So

    @Document // @Text {}

will become

    @Page // @Page // ... // @Page // @Null

and @Null will consume the preceding concatenation and disappear,
leaving:

    @Page // @Page // ... // @Page

In case of @Report and @Section's each invocation of @Section will be
@Null so the tail of the above will look

    @Page // ... // @Page // @Null & @Null & ... & @Null

and all the @Null's will disappear as in the previous example.


SY, Uwe
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