end marker

end marker

[Brian S McQueen]

Is there an equivalent to perls "__END__" for scheme scripting? It is very
handy for developing scripts.

Brian


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Re: end marker

[Paul Jarc]

Brian S McQueen <bqueen@nas.nasa.gov> wrote:
> Is there an equivalent to perls "__END__" for scheme scripting?

Not exactly, AFAIK, but you can use a #!-!# comment:
... code ...
#!
... random text ...
!#


paul


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Re: end marker

[Andreas Rottmann]

Brian S McQueen <bqueen@nas.nasa.gov> writes:

> Is there an equivalent to perls "__END__" for scheme scripting? It is very
> handy for developing scripts.
>
I assume (quit) will do the job in most cases (I don't really know the
semantics of __END__, just guessing).

Andy
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Re: end marker

[rm]

On Wed, Feb 11, 2004 at 08:53:38PM +0100, Andreas Rottmann wrote:
> Brian S McQueen <bqueen@nas.nasa.gov> writes:
> 
> > Is there an equivalent to perls "__END__" for scheme scripting? It is very
> > handy for developing scripts.
> >
> I assume (quit) will do the job in most cases (I don't really know the
> semantics of __END__, just guessing).

Well, __END__ does have some nice/strange/ugly/perlish semantic ;-)
The parser stops reading at '\n__END__' but leaves the filehandle open.
The script itself can then continue reading from this filehandle.

*--------------------------------------------------------------------- 
| #!/usr/barf/perl
| 
| while (<DATA>)
| {
|   print "Data from myself: $_";
| }
| 
| __END__
| 
| This is
| data for the script
| 
*---------------------------------------------------------------------

This can come handy for selfcontained scripts.

 Ralf Mattes



> Andy
> -- 
> Andreas Rottmann         | Rotty@ICQ      | 118634484@ICQ | a.rottmann@gmx.at
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> 
> Packages should build-depend on what they should build-depend.
> 
> 
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Re: end marker

[Paul Jarc]

rm@fabula.de wrote:
> On Wed, Feb 11, 2004 at 08:53:38PM +0100, Andreas Rottmann wrote:
>> I assume (quit) will do the job in most cases

It won't work if you read the whole file before running any of it
(e.g. guile -s function script.scm).

> Well, __END__ does have some nice/strange/ugly/perlish semantic ;-)
> The parser stops reading at '\n__END__' but leaves the filehandle open.
> The script itself can then continue reading from this filehandle.

No, that's __DATA__.  __END__ just tells the interpreter to pretend
it's EOF.


paul


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Re: end marker

[Paul Jarc]

I wrote:
> It won't work if you read the whole file before running any of it
> (e.g. guile -s function script.scm).

Eh, make that "guile -e function -s script.scm".  guile would still
read beyond (quit) (which might trigger arbitrary actions from reader
extensions), but Perl stops reading at __END__.


paul


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Re: end marker

[Stephen Compall]

prj@po.cwru.edu (Paul Jarc) writes:

> Eh, make that "guile -e function -s script.scm".  guile would still
> read beyond (quit) (which might trigger arbitrary actions from
> reader extensions), but Perl stops reading at __END__.

How far does `read' read ahead of the last s-expression it returned?
And does -s read and evaluate one s-expression at a time?

--
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Re: end marker

[Paul Jarc]

Stephen Compall <s11@member.fsf.org> wrote:
> prj@po.cwru.edu (Paul Jarc) writes:
>> Eh, make that "guile -e function -s script.scm".  guile would still
>> read beyond (quit) (which might trigger arbitrary actions from
>> reader extensions), but Perl stops reading at __END__.
>
> How far does `read' read ahead of the last s-expression it returned?

It may buffer ahead at the stdio level, but it doesn't consume any
extra characters (so everything will be visible to the next (read)),
and it doesn't call any reader-extension procedures for the extra
characters.

> And does -s read and evaluate one s-expression at a time?

Yes, but if it's used together with -e, then that probably means that
the whole script wouldn't really do much of anything just by loading
it - it defines some procedures, and then guile calls the one
specified by -e.  However, if it uses reader extensions, then those
would typically be established at the top level, outside any procedure
definition, so they would take place during the reading of the rest of
the script.

Consider this script:
  (define (x chr port)
    (format #t "~S\n" chr)
    #t)
  (read-hash-extend #\x x)
  #x
If the (read-hash-extend) were not fully evaluated before #x is read,
you'd get an error.


paul


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