Add gcd and lcm to docs

Author: mborland

doc/int128.adoc

@@ -38,7 +38,7 @@ include::int128/charconv.adoc[]
 
 include::int128/stream.adoc[]
 
-include::int128/saturating.adoc[]
+include::int128/numeric.adoc[]
 
 include::int128/examples.adoc[]
 

doc/int128/api_reference.adoc

@@ -72,6 +72,8 @@ Listed by analogous STL header.
 - <<sat_arith, `mul_sat`>>
 - <<sat_arith, `div_sat`>>
 - <<saturating_cast, `saturate_cast`>>
+- <<gcd, `gcd`>>
+- <<lcm, `lcm`>>
 
 == Enums
 

doc/int128/saturating.adoc doc/int128/numeric.adocdoc/int128/saturating.adoc renamed to doc/int128/numeric.adoc

@@ -64,4 +64,42 @@ constexpr TargetIntegerType saturate_cast(LibraryIntegerType x) noexcept;
 } // namespace boost
 ----
 
+[#gcd]
+== Greatest Common Divisor (GCD)
 
+Computes the greatest common divisor of `a` and `b`.
+
+[source, c++]
+----
+#include <boost/int128/numeric.hpp>
+
+namespace boost {
+namespace int128 {
+
+constexpr uint128_t gcd(uint128_t a, uint128_t b) noexcept;
+constexpr uint128_t gcd(const int128_t a, const int128_t b) noexcept;
+
+} // namespace int128
+} // namespace boost
+
+----
+
+[#lcm]
+== Least Common Multiple (LCM)
+
+Computes the least common multiple of `a` and `b`.
+
+[source, c++]
+----
+#include <boost/int128/numeric.hpp>
+
+namespace boost {
+namespace int128 {
+
+constexpr uint128_t lcm(uint128_t a, uint128_t b) noexcept;
+constexpr uint128_t lcm(const int128_t a, const int128_t b) noexcept;
+
+} // namespace int128
+} // namespace boost
+
+----