eval [was Re: Processing of convenience variables for scripts ...]

[Doug Evans <dje@transmeta.com>]

Richard Sharpe writes:
 > On Sun, 8 Dec 2002, Doug Evans wrote:
 > 
 > > Andrew writes:
 > >  >> The loop works, but add-symbol-file seems to be called without the
 > >  >>>
 > >  >>> convenience variables being expanded.
 > >  >>>
 > >  >>> Have it got that right?
 > >  >>>
 > >  >>> If so, what would be the first step to get them expanded?
 > >  >>
 > >  >> add-symbol-file takes constants, not expressions - so variables are not
 > >  >> expanded.  This should probably change but it's not clear how, given
 > >  >> the parser...
 > >  >
 > >  > A quick/dirty hack would be:
 > >  >
 > >  > eval .....
 > > 
 > > Can someone point me to threads on `eval'?
 > > My poor eyes can't find one.
 > 
 > I think that the intent was that someone implement eval. I can't find an 
 > existing one. Maybe my eyes are bad as well.

I recall a message from Fernando (I think) refering to the existing
threads on eval, so I was wondering where they were.

What about a $()-like command akin to bash?
Maybe spelled $`` (backquote also from bash and because $` is
a syntax that doesn't collide with anything).
It's very useful to be able to run a command and have the result be used
in another command.

For add-symbol-file, one might do

add-symbol-file $`printf %s, $name` blah...

$`` is useful regardless of how the cli is rewritten,
though perhaps in this example it's more clumsy than just $name.
OTOH, there's enormous flexibility.
It does require commands that are used with it to properly
send their output through something that can be captured in a string,
but that's a good thing for them to do anyway.