Re: how can I prevent MSI from expanding just some macros?

[Ned Arnold <nda@aps.anl.gov>]

In the interest of full disclosure, I saw that trick in databases we received from LBL ... it's likely Eric had something to do with it  :)

Just wanted to give credit where it was due ...

   Ned

---

From: "Till Straumann" <strauman@slac.stanford.edu>
To: tech-talk@aps.anl.gov
Sent: Friday, September 2, 2011 4:05:42 PM
Subject: Re: how can I prevent MSI from expanding just some macros?

On 09/02/2011 03:42 PM, Ned Arnold wrote:
> Maybe I misunderstand, but can't you simply replace the variable with
> the same variable ... like this?

Cool - I didn't know that \ escaped a $. That's exactly what I
was looking for.

Thanks
-- T.

>
> file dbAsyn_init.template
> {
> pattern
> {P , R, GROUP, NAME, DLY }
> {\$(P),\$(R), reg_data, IN0PD , "2" }
> {\$(P),\$(R), reg_data, IN1PD , "2" }
> {\$(P),\$(R), reg_data, IN2PD , "2" }
> {\$(P),\$(R), reg_data, IN3PD , "2" }
> {\$(P),\$(R), reg_data, IF_SLEEP , "2" }
>
> "It works for me" ... as they say.
>
> Ned
>
>
> ------------------------------------------------------------------------
> *From: *"Andrew Johnson" <anj@aps.anl.gov>
> *To: *tech-talk@aps.anl.gov
> *Sent: *Friday, September 2, 2011 3:01:45 PM
> *Subject: *Re: how can I prevent MSI from expanding just some macros?
>
> Hi Till,
>
> On 2011-09-02 Till Straumann wrote:
>  > I process a bunch of templates with MSI but would like the final
>  > .db file to still contain macros which are to defined when the
>  > .db file is loaded. Of course, this works for macros without
>  > a definition but I'd like to prevent MSI from expanding a macro
>  > that gives a default value:
>  >
>  > $(dont_expand=my_default)
>  >
>  > Is there a way to prevent MSI from expanding this?
>
> The obvious way is to use something other than MSI to do this particular
> expansion, but I expect it's possible to do it using MSI somehow.
>
> Maybe instead of spelling them like you do above, you would spell those
> macros
> like this:
>
> $(dont_expand$(equals)my_default)
>
> When you run MSI it will convert that string to this:
>
> $(dont_expand$(equals,undefined)my_default,undefined)
>
> But that's Ok and still legal. When you're finally ready to expand the
> dont_expand variable you also set equals='=' and you'll get this as a
> partial
> result:
>
> $(dont_expand=my_default,undefined)
>
> which should then properly expand the dont_expand variable and or set it to
> my_default if it's not defined.
>
> Not tested, and probably rather brittle...
>
> - Andrew
> --
> Optimization is the process of taking something that works and
> replacing it with something that almost works, but costs less.
> -- Roger Needham