The Trapezoidal Method with linear iterations

Let's consider the model problem
dy/dt = -20*y
y(0) = 1
0 <= t <= 2
A simple script to solve this with linear iterations can be downloaded here . Again, it uses the functions deriv.m and exact.m . We know that the solution of this problem decays, and that in fact
y(t) = exp(-20*t)

Let's look at results where the first guess for w(i+1) is obtained with Euler's method. In the following 2 graphs, we first 0 iterations, and then iterations until w(i+1)^(j) is within a certain tolerance of w(i+1)^(j-1).

Without Iterations:

With Iterations: