\\ Exponent of highest 2-power <=n.
t_2 (n) = #binary(n)-1

\\ Exponent of smallest power of 2 >= n.
t_2sup (n) = {my (k);
k=t_2(n); p=2^k; if (n==p,k,k+1)}

\\ Highest 2-power<=n.
t_pot2 (n) = 2^t_2(n)

\\ Projection on [0,1] (binary abscissa).
t_bt_A(n) = {my (p,j);
p=t_pot2(n); j=n-p; (2*j+1)/(2*p)}