// This program solves systems of equations.

use allTransforms.frink

class System
{
   /* An array of equations, parsed to expressions.  These use the
      === operator to separate the sides of the equations. */
   var equations

   /** A set of symbols that we're *not* going to solve for, for example,
       constants, user-supplied knowns, etc. */
   var ignoreSymbols = new set

   new[equationList, ignoreSet=[]] :=
   {
      // TODO:  Maybe parse strings or assignments into === equations?
      equations = equationList
      
      for ignore = ignoreSet
         addIgnoreSymbols[ignoreSet]
   }

   /** Adds the symbols in the set (or array) to the set of ignoreSymbols. */
   addIgnoreSymbols[ignoreSet] :=
   {
      for sym = ignoreSet
         ignoreSymbols.put[makeSymbol[sym]]
   }

   /** Turns a string or a symbol into a symbol. */
   makeSymbol[sym] :=
   {
      if type[s] == "Symbol"
         return s
      else
         return constructExpression["Symbol", [s]]
   }

   dump[] :=
   {
      println["Equations:"]
      for i = 0 to length[equations]-1
      {
         println["$i\t" + equations@i]
      }

      println[]
   }
}