  A general framework is proposed that includes polar codes over arbitrary
channels with arbitrary kernels. The asymptotic tradeoff among block length
$N$, code rate $R$, and error probability $P$ is analyzed.
  Given a tradeoff between $N,P$ and a tradeoff between $N,R$, we return an
interpolating tradeoff among $N,R,P$ (Theorem 5).
$\def\Capacity{\text{Capacity}}$Quantitatively, if $P=\exp(-N^{\beta^*})$ is
possible for some $\beta^*$ and if $R=\Capacity-N^{1/\mu^*}$ is possible for
some $1/\mu^*$, then $(P,R)=(\exp(-N^{\beta'}),\Capacity-N^{-1/\mu'})$ is
possible for some pair $(\beta',1/\mu')$ determined by $\beta^*$, $1/\mu^*$,
and auxiliary information. In fancy words, an error exponent regime tradeoff
plus a scaling exponent regime tradeoff implies a moderate deviations regime
tradeoff.
  The current world records are:
[arXiv:1304.4321][arXiv:1501.02444][arXiv:1806.02405] analyzing Ar{\i}kan's
codes over BEC; [arXiv:1706.02458] analyzing Ar{\i}kan's codes over AWGN; and
[arXiv:1802.02718][arXiv:1810.04298] analyzing general codes over general
channels. An attempt is made to generalize all at once (Section IX).
  As a corollary, a grafted variant of polar coding almost catches up the code
rate and error probability of random codes with complexity slightly larger than
$N\log N$ over BEC. In particular, $(P,R)=(\exp(-N^{.33}),\Capacity-N^{-.33})$
is possible (Corollary 10). In fact, all points in this triangle are possible
$(\beta',1/\mu')$-pairs. $$
  \require{enclose}
  \def\r{\phantom{\Rule{4em}{1em}{1em}}}
  \enclose{}\r^\llap{(0,1/2)}_\llap{(0,0)}
  \enclose{left,bottom,downdiagonalstrike}\r_\rlap{(1,0)}
  \enclose{}\r $$
