I've been working on some project. It should be able to do numerical and symbolic computing. But now I stuck on one problem and I don't really know how to resolve it. To be specific and short, let's say we are in package
(in-package #:brand-new-package)
Where we have symbol database
(defvar var-symbol-database (make-hash-table :test #'equal))
Reading and setting functions
(defun var-symbol (name)
(get-hash name var-symbol-database))
(defun set-var-symbol (name value)
(setf (get-hash name var-symbol-database) value))
(set-var-symbol 'temperature 300) ;K
(set-var-symbol 'f 200) ;Hz
(set-var-symbol 'k 1.3806504e-23) ;J K^-1
and now in another file (but same package) I will try to evaluate this equation
(eval '(+ 2 (var-symbol 'f)))
It won't work. Problem is that for some particular reason the value of key in hash table is.
brand-new-package::f
I though that I will solve the problem defining function like this
(set-var-symbol 1 '(var-symbol 'f)) ;Hz
But it is interpreted as
(brand-new-package::var-symbol brand-new-package::f)
The problem is that program can create many different symbols. It will compute electronic circuit equations. Program first inspect device objects like capacitors, resistors and so. It create circuit tablo by MNA.
During it many new symbols representing node voltages and currents could be created
(v1, v2, v3, i1, i2).
I needed some method to hold count and names of variables presented in equation. Because they will be passed to symbolic derivator ie (diff '(* (+ 40 v1) u2 ...) 'v1)) I came with an idea, maybe wrong, to make them reachable by index to define them as a list
'(v 1) '(v 2) '(v 3).
To make them evaluable I added to begining var-variable funcall. So list becomed
'(var-variable v 1) '(var-variable v 2) '(var-variable v 3)
But as I have written, system changes it to
'(brand-new-package::var-variable brand-new-package::v 1) '(brand-new-package::var-variable brand-new-package::v 2) '(brand-new-package::var-variable brand-new-package::v 3)
How to allow to users to acces these variables by typing (var-symbol 'v 1). I can imagine only one way. Instead of symbols use strings and export function (var-symbol). Then it will work this way
'(var-variable "v" 1)
But it is a little bit confusing.