[rand.req.urng] Rework URBG requirements for clarity and simplicitly

... by removing the redundance between the new concept and the "old" requirements.

Also fixup the reference in [rand.req.eng] to properly refer [rand.req.urng] instead of the requirements table. The table has been removed, and the reference should have been to the subclause in the first place to clearly incorporate the requirements outside of the table.

Author: CaseyCarter

Diff for: source/numerics.tex

@@ -1927,82 +1927,6 @@
  is often determined statistically.
 \end{note}
 
-\pnum
-A class \tcode{G}
-satisfies the requirements
-of a \term{uniform random bit generator}
-if the expressions shown
-in \tref{UniformRandomBitGenerator}
-are valid and have the indicated semantics,
-and if \tcode{G} also satisfies all other requirements
-of this subclause \ref{rand.req.urng}.
-In that Table and throughout this subclause:
-\begin{enumeratea}
-  \item
-    \tcode{T} is the type named by
-    \tcode{G}'s associated \tcode{result_type},
-  and
-  \item
-    \tcode{g} is a value of \tcode{G}.
-\end{enumeratea}
-
-\begin{libreqtab4d}
-  {Uniform random bit generator requirements}
-  {tab:UniformRandomBitGenerator}
-\\ \topline
-\lhdr{Expression}
-  & \chdr{Return type}
-  & \chdr{Pre/post-condition}
-  & \rhdr{Complexity}
-  \\ \capsep
-\endfirsthead
-\hline
-\lhdr{Expression}
-  & \chdr{Return type}
-  & \chdr{Pre/post-condition}
-  & \rhdr{Complexity}
-  \\ \capsep
-\endhead
-\indextext{\idxcode{result_type}!uniform random bit generator requirement}%
-\tcode{G::result_type}
-  & \tcode{T}
-  & \tcode{T} is an unsigned integer type\iref{basic.fundamental}.
-  & compile-time
-  \\ \rowsep
-\tcode{g()}%
-\indextext{\idxcode{operator()}!uniform random bit generator requirement}
-  & \tcode{T}
-  & Returns a value in the closed interval
-    $[$\tcode{G::min()}, \tcode{G::max()}$]$.
-  & amortized constant
-  \\ \rowsep
-\tcode{G::min()}%
-\indextext{\idxcode{min}!uniform random bit generator requirement}
-  & \tcode{T}
-  & Denotes the least value potentially returned
-    by \tcode{operator()}.
-  & compile-time
-  \\ \rowsep
-\tcode{G::max()}
-\indextext{\idxcode{max}!uniform random bit generator requirement}
-  & \tcode{T}
-  & Denotes the greatest value potentially returned
-    by \tcode{operator()}.
-  & compile-time
-  \\
-\end{libreqtab4d}
-
-\pnum
-The following relation shall hold:
-\tcode{G::min() < G::max()}.
-\indextext{requirements!uniform random bit generator|)}%
-\indextext{uniform random bit generator!requirements|)}
-
-\pnum
-The \libconcept{UniformRandomBitGenerator} concept is a slight relaxation of the
-uniform random bit generator requirements, in that it does not require a nested
-\grammarterm{typedef-name} \tcode{result_type}.
-
 \begin{codeblock}
 template <class G>
 concept UniformRandomBitGenerator =
@@ -2014,8 +1938,8 @@
 \end{codeblock}
 
 \pnum
-Let \tcode{g} be an object of type \tcode{G}.
-\tcode{\libconcept{UniformRandomBitGenerator}<G>} is satisfied only if
+Let \tcode{g} be an object of type \tcode{G}. \tcode{G} models
+\libconcept{UniformRandomBitGenerator} only if
 
 \begin{itemize}
 \item Both \tcode{G::min()} and \tcode{G::max()} are constant
@@ -2026,6 +1950,17 @@
 \item \tcode{g()} has amortized constant complexity.
 \end{itemize}
 
+\indextext{requirements!uniform random bit generator|)}%
+\indextext{uniform random bit generator!requirements|)}%
+\pnum
+A class \tcode{G} meets the \term{uniform random bit generator} requirements if
+\tcode{G} models \libconcept{UniformRandomBitGenerator},
+\tcode{invoke_result_t<G\&>} is an unsigned integer type\iref{basic.fundamental},
+and
+\tcode{G} provides a nested \grammarterm{typedef-name} \tcode{result_type}
+that denotes the same type as \tcode{invoke_result_t<G\&>}.
+
+
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 % Random Number Engine requirements:
 
@@ -2200,7 +2135,7 @@
       \state{e}{i+1} $= \mathsf{TA}($\state{e}{i}$)$
     and returns
       $\mathsf{GA}($\state{e}{i}$)$.
-  & per \tref{UniformRandomBitGenerator}
+  & per \ref{rand.req.urng}
   \\ \rowsep
 \tcode{e.discard(z)}%
 \indextext{\idxcode{discard}!random number engine requirement}