I’m writing a process that simulates the findRoot built-in perform utilizing the identical code that seems at chapter 6 of $textit{Programming in mathematica}$ by Paul Wellin. The code is the next.

findRoot[expr_, {var_, init_}, [Epsilon]_] :=
 Module[{xi = init, fun = Function[fvar, expr]},
  Whereas[Abs[fun[xi]] > [Epsilon],
   xi = N[xi - fun[xi]/enjoyable'[xi]]];
  {var -> xi}]

Within the textual content, the code is examined with success, however after I check it it would not works. For instance,

In[5]:= findRoot[x^2 - 2, {x, 2.0}, 0.0001]

Out[5]= {x -> 2.}

I attempted to vary the variable fvar by var, and this system works, however it is a reuse of names that makes mathematica shade the variable var in purple.

findRoot[expr_ == val_, {var_, init_}, [Epsilon]_] :=
 Module[{xi = init, fun = Function[var, expr - val]},
  Whereas[Abs[fun[xi]] > [Epsilon],
   xi = N[xi - fun[xi]/enjoyable'[xi]]];
  {var -> xi}]

I would like some suggestion to clear this challenge.