Update examples and output

Author: mborland

doc/modules/ROOT/pages/examples.adoc

@@ -45,6 +45,19 @@ From BOOST_INT128_INT128_C(min): -170141183460469231731687303715884105728
 === Default and Copy Construction ===
 Default constructed: 0
 Copy constructed: 340282366920938463463374607431768211455
+
+=== Floating-Point Construction ===
+uint128_t from 12345.9 (truncated): 12345
+int128_t from -12345.9 (truncated toward zero): -12345
+uint128_t from 2^100: 1267650600228229401496703205376
+
+=== Floating-Point Edge Cases ===
+uint128_t from NaN: 0
+int128_t from NaN: 0
+uint128_t from -1.0 (clamped to zero): 0
+uint128_t from +infinity (saturates to UINT128_MAX): 340282366920938463463374607431768211455
+int128_t from 1e40 (saturates to INT128_MAX): 170141183460469231731687303715884105727
+int128_t from -1e40 (saturates to INT128_MIN): -170141183460469231731687303715884105728
 ----
 ====
 

examples/construction.cpp

@@ -90,5 +90,45 @@ int main()
     const uint128_t copied {from_macro};
     std::cout << "Copy constructed: " << copied << std::endl;
 
+    std::cout << "\n=== Floating-Point Construction ===" << std::endl;
+
+    // Floating-point construction truncates toward zero, matching the behavior of
+    // a static_cast from a floating-point type to a built-in integer.
+    constexpr uint128_t from_double {12345.9};
+    std::cout << "uint128_t from 12345.9 (truncated): " << from_double << std::endl;
+
+    constexpr int128_t from_negative_double {-12345.9};
+    std::cout << "int128_t from -12345.9 (truncated toward zero): " << from_negative_double << std::endl;
+
+    // Values that exceed the 64-bit range are routed through the full 128-bit decomposition.
+    const double two_to_the_100 {1.2676506002282294e30};  // 2^100
+    const uint128_t large_from_double {two_to_the_100};
+    std::cout << "uint128_t from 2^100: " << large_from_double << std::endl;
+
+    std::cout << "\n=== Floating-Point Edge Cases ===" << std::endl;
+
+    // NaN yields zero for both signed and unsigned (mirrors libgcc's __fix(uns)Xfti).
+    const double nan_value {std::numeric_limits<double>::quiet_NaN()};
+    const uint128_t unsigned_from_nan {nan_value};
+    const int128_t signed_from_nan {nan_value};
+    std::cout << "uint128_t from NaN: " << unsigned_from_nan << std::endl;
+    std::cout << "int128_t from NaN: " << signed_from_nan << std::endl;
+
+    // Negative values are clamped to zero when constructing uint128_t.
+    const uint128_t unsigned_from_negative {-1.0};
+    std::cout << "uint128_t from -1.0 (clamped to zero): " << unsigned_from_negative << std::endl;
+
+    // Positive overflow saturates: anything >= 2^128 (including +infinity) becomes UINT128_MAX.
+    const double infinity {std::numeric_limits<double>::infinity()};
+    const uint128_t saturated_unsigned {infinity};
+    std::cout << "uint128_t from +infinity (saturates to UINT128_MAX): " << saturated_unsigned << std::endl;
+
+    // For int128_t, values >= 2^127 saturate to INT128_MAX and values <= -2^127 saturate to INT128_MIN.
+    const double huge {1e40};  // Well beyond 2^127 (~ 1.7e38)
+    const int128_t saturated_positive {huge};
+    const int128_t saturated_negative {-huge};
+    std::cout << "int128_t from 1e40 (saturates to INT128_MAX): " << saturated_positive << std::endl;
+    std::cout << "int128_t from -1e40 (saturates to INT128_MIN): " << saturated_negative << std::endl;
+
     return 0;
 }