diff --git a/README.md b/README.md
index 2deadfa01..f1c405c0e 100644
--- a/README.md
+++ b/README.md
@@ -99,7 +99,7 @@ Procedures for each standard are provided by the following R7RS-style libraries:
 cmake -B build -DCMAKE_BUILD_TYPE=Release
 cd build
 make package
-sudo apt install build/meevax_0.5.5_amd64.deb
+sudo apt install build/meevax_0.5.6_amd64.deb
 ```
 
 or
@@ -131,9 +131,9 @@ sudo rm -rf /usr/local/share/meevax
 
 | Target Name | Description
 |-------------|-------------
-| `all`       | Build shared-library `libmeevax.0.5.5.so` and executable `meevax`
+| `all`       | Build shared-library `libmeevax.0.5.6.so` and executable `meevax`
 | `test`      | Test executable `meevax`
-| `package`   | Generate debian package `meevax_0.5.5_amd64.deb`
+| `package`   | Generate debian package `meevax_0.5.6_amd64.deb`
 | `install`   | Copy files into `/usr/local` directly
 
 ## Usage
diff --git a/VERSION b/VERSION
index d1d899fa3..b49b25336 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-0.5.5
+0.5.6
diff --git a/basis/r4rs.ss b/basis/r4rs.ss
index 0d155260e..e0d601a0b 100644
--- a/basis/r4rs.ss
+++ b/basis/r4rs.ss
@@ -42,10 +42,33 @@
           (only (meevax continuation) call-with-current-continuation)
           (prefix (only (meevax environment) load) %)
           (only (meevax function) procedure?)
-          (meevax inexact)
+          (only (meevax inexact) exp log sqrt sin cos tan asin acos atan)
           (meevax list)
           (only (meevax macro-transformer) er-macro-transformer identifier?)
-          (meevax number)
+          (only (meevax number)
+                number?
+                complex?
+                real?
+                rational?
+                integer?
+                = < > <= >=
+                + * - /
+                abs
+                % ; deprecated
+                ratio-numerator ; deprecated
+                ratio-denominator ; deprecated
+                floor ceiling truncate round
+                expt
+                exact inexact
+                string->number
+
+                ; to be removed
+                exact-integer? ; r7rs
+                imaginary?
+                ratio?
+                single-float?
+                double-float?
+                )
           (meevax pair)
           (meevax port)
           (prefix (meevax read) %)
diff --git a/include/meevax/kernel/number.hpp b/include/meevax/kernel/number.hpp
index 6e69f4a29..ed02016c8 100644
--- a/include/meevax/kernel/number.hpp
+++ b/include/meevax/kernel/number.hpp
@@ -363,6 +363,8 @@ inline namespace number
 
   auto is_integer(object const&) -> bool;
 
+  auto is_exact(object const&) -> bool;
+
   auto is_finite(object const&) -> bool;
 
   auto is_infinite(object const&) -> bool;
diff --git a/src/kernel/boot.cpp b/src/kernel/boot.cpp
index 40df6f89f..5cc111d01 100644
--- a/src/kernel/boot.cpp
+++ b/src/kernel/boot.cpp
@@ -540,26 +540,35 @@ inline namespace kernel
         return is_integer(xs[0]);
       });
 
+      library.define<predicate>("exact?", [](let const& xs)
+      {
+        return is_exact(xs[0]);
+      });
+
       library.define<predicate>("exact-integer?", [](let const& xs)
       {
         return xs[0].is<exact_integer>();
       });
 
+      // TODO REMOVE
       library.define<predicate>("imaginary?", [](let const& xs)
       {
         return xs[0].is<complex>();
       });
 
+      // TODO REMOVE
       library.define<predicate>("ratio?", [](let const& xs)
       {
         return xs[0].is<ratio>();
       });
 
+      // TODO REMOVE
       library.define<predicate>("single-float?", [](let const& xs)
       {
         return xs[0].is<float>();
       });
 
+      // TODO REMOVE
       library.define<predicate>("double-float?", [](let const& xs)
       {
         return xs[0].is<double>();
@@ -624,6 +633,7 @@ inline namespace kernel
         }
       });
 
+      // TODO RENAME
       library.define<function>("%", [](let const& xs)
       {
         return xs[0] % xs[1];
@@ -634,6 +644,10 @@ inline namespace kernel
         return abs(xs[0]);
       });
 
+      // TODO QUOTIENT
+      // TODO REMAINDER
+      // TODO MODULO
+
       library.define<function>("ratio-numerator", [](let const& xs)
       {
         return make(xs[0].as<ratio>().numerator());
diff --git a/src/kernel/number.cpp b/src/kernel/number.cpp
index a7930373c..4f24a7d8f 100644
--- a/src/kernel/number.cpp
+++ b/src/kernel/number.cpp
@@ -659,6 +659,25 @@ inline namespace number
     return test(f, x);
   }
 
+  auto is_exact(object const& x) -> bool
+  {
+    auto f = [](auto const& x)
+    {
+      using T = std::decay_t<decltype(x)>;
+
+      if constexpr (std::is_same_v<T, complex>)
+      {
+        return is_exact(x.real()) and is_exact(x.imag());
+      }
+      else
+      {
+        return std::is_same_v<T, ratio> or std::is_same_v<T, exact_integer>;
+      }
+    };
+
+    return test(f, x);
+  }
+
   auto is_finite(object const& x) -> bool
   {
     return not is_infinite(x);