Global and local variables and environments

Hi all,

I use OCEAN scripts to simulate circuits. Typically I have one (or
more) script per circuit. At the moment all the variables in my
scripts are global.

However I'd like to reduce the number of global variables, or at least
make such that some variables that are used to simulate one circuit
are invisible when simulating a second one.

I do not want to use let(), because

* I'd like to avoid to explicitly declare each variable
* I still want to access some variables interactively from the CIW
at the end of the script

I thought something like a MATLAB workspace could do the job. I read
about SKILL++ environments, and I thought that they work like MATLAB
workspaces. However:

* Can I use SKILL++ environment in scripts (i.e. non-
interactively)?
* Can you use OCEAN functions directly inside SKILL++ scripts?
* Is there anything with environments functionality that can be
used in (plain) SKILL scripts?
* How are environments setup and used in a script? (simple code
example would help here)

In case I cannot use environments or they turn out to be not a good
solution for me:

* What other options do I have to share/hide variables?
* How can I clear all the variables?

Thanks for any suggestion.


As an example of how I would like to use this functionality, consider
the case where I want to have "workspaces", each dedicated to a
different circuit/script. All variables used in the script
corresponding to one circuit should be hidden when simulating a second
one. If this is not easily possible, than at least clear all variables
before calling a second script would help.

 

[Andrew Beckett]

Hi Marco,

Some answers embedded...

marcoballins@gmail.com wrote, on 08/27/08 09:45:

Hi all,

I use OCEAN scripts to simulate circuits. Typically I have one (or
more) script per circuit. At the moment all the variables in my
scripts are global.

However I'd like to reduce the number of global variables, or at least
make such that some variables that are used to simulate one circuit
are invisible when simulating a second one.

I do not want to use let(), because

* I'd like to avoid to explicitly declare each variable
* I still want to access some variables interactively from the CIW
at the end of the script

OK. But let() is really the way to do this in SKILL...

I thought something like a MATLAB workspace could do the job. I read
about SKILL++ environments, and I thought that they work like MATLAB
workspaces. However:

Not really. A SKILL++ environment is a lexical scope - and generally you'd
still need to use let() to define a new environment and declare the variables
within them.

* Can I use SKILL++ environment in scripts (i.e. non-
interactively)?

yes

* Can you use OCEAN functions directly inside SKILL++ scripts?

yes

* Is there anything with environments functionality that can be
used in (plain) SKILL scripts?

not really. An environment is created via a SKILL++ lexical scope - you
can access the current environment from SKILL++, but not see what's
inside it (unless you're in debug mode).

* How are environments setup and used in a script? (simple code
example would help here)

I don't think this is the right solution, although perhaps the code
I wrote below might help?

In case I cannot use environments or they turn out to be not a good
solution for me:

* What other options do I have to share/hide variables?
* How can I clear all the variables?

Thanks for any suggestion.


As an example of how I would like to use this functionality, consider
the case where I want to have "workspaces", each dedicated to a
different circuit/script. All variables used in the script
corresponding to one circuit should be hidden when simulating a second
one. If this is not easily possible, than at least clear all variables
before calling a second script would help.

A simple solution would probably be just to use a table to store variables.
However, I just wrote a bit of SKILL that might be an elegant solution
to this. See the examples at the top of the code. You have to use
the abVarSet/abVarGet macros to set and get variable values rather than
using the "=" operator, but it might suit your needs. Note that the
file containing the code MUST retain a ".ils" suffix to allow it to
be seen as SKILL++. This is in fact taking advantage of SKILL++
lexical environments to hide the data ;->


/* abWorkspace.ils

Author A.D.Beckett
Group Custom IC (UK), Cadence Design Systems Ltd.
Language SKILL
Date Aug 29, 2008
Modified
By

A simple workspace package. Use functions like this:

abWorkspace->set("first")
abVarSet(myVar 23)
abVarGet(myVar) => 23
abVarSet(myVar2 46)
abWorkspace->set("another")
abVarSet(myVar 200)
abVarGet(myVar) => 200
abWorkspace->set("first")
abVarGet(myVar) => 23
abWorkspace->delete("another")

***************************************************

SCCS Info: @(#) abWorkspace.ils 08/29/08.11:29:15 1.1

*/

(importSkillVar abWorkspace)
(setq abWorkspace
(let (currentWs (workspaces (makeTable 'workspaces nil)))
;----------------------------------------------------------------
; Sets the current workspace to either an existing
; named workspace, or creates a new one
;----------------------------------------------------------------
(defun set (wsName)
(let (ws)
(setq ws
(or (arrayref workspaces wsName)
(create wsName))
)
(setq currentWs ws)
)
)
;----------------------------------------------------------------
; Gets the current workspace. Used by the abVarSet/abVarGet
; macros
;----------------------------------------------------------------
(defun get ()
currentWs
)
;----------------------------------------------------------------
; Deletes a workspace, and zaps the current workspace if
; it is the one being deleted
;----------------------------------------------------------------
(defun delete (wsName)
(when (eq (remove wsName workspaces) currentWs)
(setq currentWs nil))
t
)
;----------------------------------------------------------------
; Create a new workspace. This is also a lexical
; environment with functions to set and get values
; from the table
;----------------------------------------------------------------
(defun create (wsName)
(let ((table (makeTable 'workspace)))
(defun set (var val)
(setarray table var val)
)
(defun get (var)
(arrayref table var)
)
(setarray workspaces wsName
(list nil 'set set 'get get))
)
)
;----------------------------------------------------------------
; The list of available functions from the package
;----------------------------------------------------------------
(list nil 'set set 'get get 'delete delete)
)
)

;------------------------------------------------------------------------
; Macros to make setting and getting variables in the current workspace
; easier. Saves having to quote the variable names.
;------------------------------------------------------------------------
(defmacro abVarSet (varName value)
`(funcall
(getq
(or
(funcall (getq abWorkspace get))
(error "No current workspace")
)
set)
(quote ,varName) ,value)
)
(defmacro abVarGet (varName)
`(funcall
(getq
(or
(funcall (getq abWorkspace get))
(error "No current workspace")
)
get)
(quote ,varName))
)

 

Thanks Andrew! the script will prove a useful source for tricks and
solutions (and I actually still have to understand all the details).
I just thought about another possible approach: using structures,
defined defstruct, to hold all variables of a script/simulation
But I still do not know the pros and cons (regarding to my goal of
simulating a circuit in a script, and then simulating a second circuit
in another script without risks that it uses the variables o the other
because some variables have common names).

Kind regards,
Marco