diff --git a/README.md b/README.md
index 2684bbbe5..b707ee102 100644
--- a/README.md
+++ b/README.md
@@ -97,9 +97,9 @@ Then, select one of the following targets and `make` it according to your purpos
 
 | Target      | Description
 |-------------|-------------
-| `all`       | Build shared-library `libmeevax.0.5.284.so` and executable `meevax`.
+| `all`       | Build shared-library `libmeevax.0.5.285.so` and executable `meevax`.
 | `install`   | Copy files into `/usr/local` directly.
-| `package`   | Generate debian package `meevax_0.5.284_amd64.deb` (only Ubuntu). The generated package can be installed by `sudo apt install build/meevax_0.5.284_amd64.deb`.
+| `package`   | Generate debian package `meevax_0.5.285_amd64.deb` (only Ubuntu). The generated package can be installed by `sudo apt install build/meevax_0.5.285_amd64.deb`.
 | `test`      | Test executable `meevax`. This target requires Valgrind to be installed.
 | `uninstall` | Remove files copied to `/usr/local` directly by target `install`.
 
diff --git a/VERSION b/VERSION
index 97bd45ba8..10c6f5664 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-0.5.284
+0.5.285
diff --git a/basis/srfi-144.ss b/basis/srfi-144.ss
index 3605b85f7..b8b9cfb2f 100644
--- a/basis/srfi-144.ss
+++ b/basis/srfi-144.ss
@@ -6,10 +6,12 @@
             binary64-epsilon
             binary64-exponent
             binary64-fractional-part
-            binary64-integer-exponent
+            binary64-integer-log-binary
             binary64-integral-part
+            binary64-log-binary
             binary64-max
             binary64-min
+            binary64-normalized-fraction
             copy-sign
             e
             euler
@@ -48,7 +50,8 @@
           flonum fladjacent flcopysign make-flonum
 
           flinteger-fraction flexponent flinteger-exponent
-          ; flnormalized-fraction-exponent flsign-bit
+          flnormalized-fraction-exponent
+          ;flsign-bit
           ;
           ; flonum? fl=? fl<? fl>? fl<=? fl>=?
           ; flunordered? flinteger? flzero? flpositive? flnegative?
@@ -173,8 +176,12 @@
            (values (binary64-integral-part x)
                    (binary64-fractional-part x)))
 
-         (define flexponent binary64-exponent)
+         (define flexponent binary64-log-binary)
 
-         (define flinteger-exponent binary64-integer-exponent)
+         (define flinteger-exponent binary64-integer-log-binary)
+
+         (define (flnormalized-fraction-exponent x)
+           (values (binary64-normalized-fraction x)
+                   (binary64-exponent x)))
          )
   )
diff --git a/src/kernel/boot.cpp b/src/kernel/boot.cpp
index b81e4f1f9..9f2ae2d30 100644
--- a/src/kernel/boot.cpp
+++ b/src/kernel/boot.cpp
@@ -583,16 +583,29 @@ namespace meevax::inline kernel
         return make(std::modf(car(xs).as<double>(), &integral_part));
       });
 
-      library.define<procedure>("binary64-exponent", [](let const& xs)
+      library.define<procedure>("binary64-log-binary", [](let const& xs)
       {
         return make(std::logb(car(xs).as<double>()));
       });
 
-      library.define<procedure>("binary64-integer-exponent", [](let const& xs)
+      library.define<procedure>("binary64-integer-log-binary", [](let const& xs)
       {
         return make<exact_integer>(std::ilogb(car(xs).as<double>()));
       });
 
+      library.define<procedure>("binary64-normalized-fraction", [](let const& xs)
+      {
+        auto exponent = 0;
+        return make(std::frexp(car(xs).as<double>(), &exponent));
+      });
+
+      library.define<procedure>("binary64-exponent", [](let const& xs)
+      {
+        auto exponent = 0;
+        std::frexp(car(xs).as<double>(), &exponent);
+        return make<exact_integer>(exponent);
+      });
+
       library.define<double>("e", std::numbers::e);
 
       library.define<double>("pi", std::numbers::pi);