For 21.1, I improved the interface to the Tiny C compiler. It is now possible to write functions, which are automatically compiled. These functions consist of some macros and much C code.

For an example, the code for the Hofstadter-Conway sequence in this notebook now is

function tinyc hofstadter (n) ...
  ## Computes n elements of the Hofstadter-Conway sequence.
  ARG_INT(n);
  CHECK(n>2,"Need an integer larger than 2.");
  RES_DOUBLE_MATRIX(m,1,n);
  m[0]=m[1]=1.0;
  int i;
  for (i=2; i<n; i++)
  {
    int k=(int)m[i-1];
    m[i]=m[k-1]+m[i-k];
  }
endfunction

The Euler version is much clearer, but about 100 times slower. I had some fun generating a so-called Brownian tree with a bit of C code.

Along the way, I noticed an error in the Mandelbrot notebook. Now the magnificent image on this page looks much better.