Re: Symbolic equation solving in Lua

[Albert Chan <albertmcchan@...>]

On Apr 30, 2018, at 7:11 AM, Gavin Wraith <gavin@wra1th.plus.com> wrote:

fixpoint = function (f)
          local g = guess
          while math.abs(g-f(g)) < epsilon do
             g = g - f(g)/df(g)
          end
          return g
          end

Using while do loop is a bad idea, as it can easily get 

into infinite loop.  It would be better if the solver "give-up" 

if it cannot converge within some maximum iterations.

Another problem is the df function.

A symbolic df function may be hard to get (or messy)

Even the f function may be hard to get.

Most engineering problem involve simultaneous system of

equations, which were hard to simplify into a single f

It is much easier using, say TK solver, instead of Lua.

Instead of a bunch of equations for solving different variable,

Just leave the input field(s) blank (or guess values), and type !

Excel spreadsheet solver is another option.