====== Namespace std::bit  ======

This namespace contains bit-manipulation functions that can make the ACT description more legible.

<code act>
export template<pint N, W> function repeat(int<W> x) : int<N*W>;
</code>
This concatenates ''N'' copies of the ''W''-bit input ''x'' to create an output of width ''N*W''.


<code act>
export template<pint W, W2> function sign_extend(int<W> x) : int<W2>;
</code>
This sign-extends the integer ''x'' (bitwidth ''W'') to bitwidth ''W2''. ''W2'' must be strictly larger than ''W''.


<code act>
export template<pint W> function rol(int<W> x) : int<W>;
</code>
Left rotate the ''W'' bit integer by 1. The MSB of ''x'' becomes the LSB of the result (rotating shift).

<code act>
export template<pint W> function ror(int<W> x) : int<W>;
</code>
Right rotate ''x'' by one, with the LSB of ''x'' becoming the MSB of the result.

<code act>
export template<pint W>  function find_msb_pos(int<W> x) : int<std::ceil_log2(W)>;
</code>
This function assumes that ''x'' is non-zero, and returns the bit position of the most significant one in ''x''.

<code act>
export template<pint W> function popcount(int<W> x) : int<std::ceil_log2(W+1)>;
</code>
This function returns a count of the number of bits of ''x'' that are set to 1.