diff --git a/README b/README
index 4188cc4f..ef86dff9 100644
--- a/README
+++ b/README
@@ -30,6 +30,7 @@ constexpr バリアント (Variants)
 constexpr アルゴリズム (Algorithms)
     sprout/algorithm.hpp
     sprout/numeric.hpp
+    sprout/numeric/dft.hpp
 
 constexpr 範囲アルゴリズム (Range algorithms)
     sprout/range/algorithm.hpp
diff --git a/sprout/functional/dft.hpp b/sprout/functional/dft.hpp
deleted file mode 100644
index 0e7ba62f..00000000
--- a/sprout/functional/dft.hpp
+++ /dev/null
@@ -1,11 +0,0 @@
-#ifndef SPROUT_FUNCTIONAL_DFT_HPP
-#define SPROUT_FUNCTIONAL_DFT_HPP
-
-#include <sprout/config.hpp>
-#include <sprout/functional/dft/dft.hpp>
-#include <sprout/functional/dft/idft.hpp>
-#include <sprout/functional/dft/dft_element.hpp>
-#include <sprout/functional/dft/idft_element.hpp>
-
-#endif	// #ifndef SPROUT_FUNCTIONAL_DFT_HPP
-
diff --git a/sprout/functional/dft/dft.hpp b/sprout/functional/dft/dft.hpp
deleted file mode 100644
index e567013e..00000000
--- a/sprout/functional/dft/dft.hpp
+++ /dev/null
@@ -1,8 +0,0 @@
-#ifndef SPROUT_FUNCTIONAL_DFT_DFT_HPP
-#define SPROUT_FUNCTIONAL_DFT_DFT_HPP
-
-#include <sprout/config.hpp>
-#include <sprout/functional/dft/fixed/dft.hpp>
-#include <sprout/functional/dft/fit/dft.hpp>
-
-#endif	// #ifndef SPROUT_FUNCTIONAL_DFT_DFT_HPP
diff --git a/sprout/functional/dft/idft.hpp b/sprout/functional/dft/idft.hpp
deleted file mode 100644
index 6fb05b7a..00000000
--- a/sprout/functional/dft/idft.hpp
+++ /dev/null
@@ -1,8 +0,0 @@
-#ifndef SPROUT_FUNCTIONAL_DFT_IDFT_HPP
-#define SPROUT_FUNCTIONAL_DFT_IDFT_HPP
-
-#include <sprout/config.hpp>
-#include <sprout/functional/dft/fixed/idft.hpp>
-#include <sprout/functional/dft/fit/idft.hpp>
-
-#endif	// #ifndef SPROUT_FUNCTIONAL_DFT_IDFT_HPP
diff --git a/sprout/functional/fft.hpp b/sprout/functional/fft.hpp
deleted file mode 100644
index a6bd8c96..00000000
--- a/sprout/functional/fft.hpp
+++ /dev/null
@@ -1,8 +0,0 @@
-#ifndef SPROUT_FUNCTIONAL_FFT_HPP
-#define SPROUT_FUNCTIONAL_FFT_HPP
-
-#include <sprout/config.hpp>
-#include <sprout/functional/fft/bitrev_table.hpp>
-
-#endif	// #ifndef SPROUT_FUNCTIONAL_FFT_HPP
-
diff --git a/sprout/functional/fft/bitrev_table.hpp b/sprout/functional/fft/bitrev_table.hpp
deleted file mode 100644
index 75a30652..00000000
--- a/sprout/functional/fft/bitrev_table.hpp
+++ /dev/null
@@ -1,8 +0,0 @@
-#ifndef SPROUT_FUNCTIONAL_FFT_BITREV_TABLE_HPP
-#define SPROUT_FUNCTIONAL_FFT_BITREV_TABLE_HPP
-
-#include <sprout/config.hpp>
-#include <sprout/functional/fft/fixed/bitrev_table.hpp>
-#include <sprout/functional/fft/fit/bitrev_table.hpp>
-
-#endif	// #ifndef SPROUT_FUNCTIONAL_FFT_BITREV_TABLE_HPP
diff --git a/sprout/numeric/dft.hpp b/sprout/numeric/dft.hpp
new file mode 100644
index 00000000..662e2904
--- /dev/null
+++ b/sprout/numeric/dft.hpp
@@ -0,0 +1,11 @@
+#ifndef SPROUT_NUMERIC_DFT_HPP
+#define SPROUT_NUMERIC_DFT_HPP
+
+#include <sprout/config.hpp>
+#include <sprout/numeric/dft/dft.hpp>
+#include <sprout/numeric/dft/idft.hpp>
+#include <sprout/numeric/dft/dft_element.hpp>
+#include <sprout/numeric/dft/idft_element.hpp>
+
+#endif	// #ifndef SPROUT_NUMERIC_DFT_HPP
+
diff --git a/sprout/functional/dft/detail/dft_element_gen.hpp b/sprout/numeric/dft/detail/dft_element_gen.hpp
similarity index 84%
rename from sprout/functional/dft/detail/dft_element_gen.hpp
rename to sprout/numeric/dft/detail/dft_element_gen.hpp
index 65c4e6f0..193046e1 100644
--- a/sprout/functional/dft/detail/dft_element_gen.hpp
+++ b/sprout/numeric/dft/detail/dft_element_gen.hpp
@@ -1,5 +1,5 @@
-#ifndef SPROUT_FUNCTIONAL_DFT_DETAIL_DFT_ELEMENT_GEN_HPP
-#define SPROUT_FUNCTIONAL_DFT_DETAIL_DFT_ELEMENT_GEN_HPP
+#ifndef SPROUT_NUMERIC_DFT_DETAIL_DFT_ELEMENT_GEN_HPP
+#define SPROUT_NUMERIC_DFT_DETAIL_DFT_ELEMENT_GEN_HPP
 
 #include <cmath>
 #include <iterator>
@@ -37,4 +37,4 @@ namespace sprout {
 	}	// namespace detail
 }	// namespace sprout
 
-#endif	// #ifndef SPROUT_FUNCTIONAL_DFT_DETAIL_DFT_ELEMENT_GEN_HPP
+#endif	// #ifndef SPROUT_NUMERIC_DFT_DETAIL_DFT_ELEMENT_GEN_HPP
diff --git a/sprout/numeric/dft/dft.hpp b/sprout/numeric/dft/dft.hpp
new file mode 100644
index 00000000..40f0c689
--- /dev/null
+++ b/sprout/numeric/dft/dft.hpp
@@ -0,0 +1,8 @@
+#ifndef SPROUT_NUMERIC_DFT_DFT_HPP
+#define SPROUT_NUMERIC_DFT_DFT_HPP
+
+#include <sprout/config.hpp>
+#include <sprout/numeric/dft/fixed/dft.hpp>
+#include <sprout/numeric/dft/fit/dft.hpp>
+
+#endif	// #ifndef SPROUT_NUMERIC_DFT_DFT_HPP
diff --git a/sprout/functional/dft/dft_element.hpp b/sprout/numeric/dft/dft_element.hpp
similarity index 80%
rename from sprout/functional/dft/dft_element.hpp
rename to sprout/numeric/dft/dft_element.hpp
index 3e8528f4..014910f1 100644
--- a/sprout/functional/dft/dft_element.hpp
+++ b/sprout/numeric/dft/dft_element.hpp
@@ -1,9 +1,9 @@
-#ifndef SPROUT_FUNCTIONAL_DFT_FIXED_DFT_ELEMENT_HPP
-#define SPROUT_FUNCTIONAL_DFT_FIXED_DFT_ELEMENT_HPP
+#ifndef SPROUT_NUMERIC_DFT_FIXED_DFT_ELEMENT_HPP
+#define SPROUT_NUMERIC_DFT_FIXED_DFT_ELEMENT_HPP
 
 #include <iterator>
 #include <sprout/config.hpp>
-#include <sprout/functional/dft/detail/dft_element_gen.hpp>
+#include <sprout/numeric/dft/detail/dft_element_gen.hpp>
 #include <sprout/math/constants.hpp>
 #include HDR_ITERATOR_SSCRISK_CEL_OR_SPROUT
 
@@ -45,4 +45,4 @@ namespace sprout {
 	}
 }	// namespace sprout
 
-#endif	// #ifndef SPROUT_FUNCTIONAL_DFT_FIXED_DFT_ELEMENT_HPP
+#endif	// #ifndef SPROUT_NUMERIC_DFT_FIXED_DFT_ELEMENT_HPP
diff --git a/sprout/functional/dft/fit/dft.hpp b/sprout/numeric/dft/fit/dft.hpp
similarity index 84%
rename from sprout/functional/dft/fit/dft.hpp
rename to sprout/numeric/dft/fit/dft.hpp
index 294d280b..34e5a41a 100644
--- a/sprout/functional/dft/fit/dft.hpp
+++ b/sprout/numeric/dft/fit/dft.hpp
@@ -1,10 +1,10 @@
-#ifndef SPROUT_FUNCTIONAL_DFT_FIT_DFT_HPP
-#define SPROUT_FUNCTIONAL_DFT_FIT_DFT_HPP
+#ifndef SPROUT_NUMERIC_DFT_FIT_DFT_HPP
+#define SPROUT_NUMERIC_DFT_FIT_DFT_HPP
 
 #include <sprout/config.hpp>
 #include <sprout/container/traits.hpp>
 #include <sprout/container/functions.hpp>
-#include <sprout/functional/dft/fixed/dft.hpp>
+#include <sprout/numeric/dft/fixed/dft.hpp>
 #include <sprout/algorithm/fit/result_of.hpp>
 #include <sprout/sub_array.hpp>
 #include HDR_ALGORITHM_SSCRISK_CEL_OR_SPROUT
@@ -43,4 +43,4 @@ namespace sprout {
 	}	// namespace fit
 }	// namespace sprout
 
-#endif	// #ifndef SPROUT_FUNCTIONAL_DFT_FIT_DFT_HPP
+#endif	// #ifndef SPROUT_NUMERIC_DFT_FIT_DFT_HPP
diff --git a/sprout/functional/dft/fit/idft.hpp b/sprout/numeric/dft/fit/idft.hpp
similarity index 84%
rename from sprout/functional/dft/fit/idft.hpp
rename to sprout/numeric/dft/fit/idft.hpp
index 9a63c573..f818ca49 100644
--- a/sprout/functional/dft/fit/idft.hpp
+++ b/sprout/numeric/dft/fit/idft.hpp
@@ -1,10 +1,10 @@
-#ifndef SPROUT_FUNCTIONAL_DFT_FIT_IDFT_HPP
-#define SPROUT_FUNCTIONAL_DFT_FIT_IDFT_HPP
+#ifndef SPROUT_NUMERIC_DFT_FIT_IDFT_HPP
+#define SPROUT_NUMERIC_DFT_FIT_IDFT_HPP
 
 #include <sprout/config.hpp>
 #include <sprout/container/traits.hpp>
 #include <sprout/container/functions.hpp>
-#include <sprout/functional/dft/fixed/idft.hpp>
+#include <sprout/numeric/dft/fixed/idft.hpp>
 #include <sprout/algorithm/fit/result_of.hpp>
 #include <sprout/sub_array.hpp>
 #include HDR_ALGORITHM_SSCRISK_CEL_OR_SPROUT
@@ -43,4 +43,4 @@ namespace sprout {
 	}	// namespace fit
 }	// namespace sprout
 
-#endif	// #ifndef SPROUT_FUNCTIONAL_DFT_FIT_IDFT_HPP
+#endif	// #ifndef SPROUT_NUMERIC_DFT_FIT_IDFT_HPP
diff --git a/sprout/functional/dft/fixed/dft.hpp b/sprout/numeric/dft/fixed/dft.hpp
similarity index 88%
rename from sprout/functional/dft/fixed/dft.hpp
rename to sprout/numeric/dft/fixed/dft.hpp
index 4c5fc491..94161e17 100644
--- a/sprout/functional/dft/fixed/dft.hpp
+++ b/sprout/numeric/dft/fixed/dft.hpp
@@ -1,5 +1,5 @@
-#ifndef SPROUT_FUNCTIONAL_DFT_FIXED_DFT_HPP
-#define SPROUT_FUNCTIONAL_DFT_FIXED_DFT_HPP
+#ifndef SPROUT_NUMERIC_DFT_FIXED_DFT_HPP
+#define SPROUT_NUMERIC_DFT_FIXED_DFT_HPP
 
 #include <sprout/config.hpp>
 #include <sprout/index_tuple.hpp>
@@ -7,7 +7,7 @@
 #include <sprout/container/functions.hpp>
 #include <sprout/iterator/operation.hpp>
 #include <sprout/algorithm/fixed/result_of.hpp>
-#include <sprout/functional/dft/dft_element.hpp>
+#include <sprout/numeric/dft/dft_element.hpp>
 #include HDR_ITERATOR_SSCRISK_CEL_OR_SPROUT
 
 namespace sprout {
@@ -68,4 +68,4 @@ namespace sprout {
 	using sprout::fixed::dft;
 }	// namespace sprout
 
-#endif	// #ifndef SPROUT_FUNCTIONAL_DFT_FIXED_DFT_HPP
+#endif	// #ifndef SPROUT_NUMERIC_DFT_FIXED_DFT_HPP
diff --git a/sprout/functional/dft/fixed/idft.hpp b/sprout/numeric/dft/fixed/idft.hpp
similarity index 88%
rename from sprout/functional/dft/fixed/idft.hpp
rename to sprout/numeric/dft/fixed/idft.hpp
index 10d6a9cc..45aebd62 100644
--- a/sprout/functional/dft/fixed/idft.hpp
+++ b/sprout/numeric/dft/fixed/idft.hpp
@@ -1,5 +1,5 @@
-#ifndef SPROUT_FUNCTIONAL_DFT_FIXED_IDFT_HPP
-#define SPROUT_FUNCTIONAL_DFT_FIXED_IDFT_HPP
+#ifndef SPROUT_NUMERIC_DFT_FIXED_IDFT_HPP
+#define SPROUT_NUMERIC_DFT_FIXED_IDFT_HPP
 
 #include <sprout/config.hpp>
 #include <sprout/index_tuple.hpp>
@@ -7,7 +7,7 @@
 #include <sprout/container/functions.hpp>
 #include <sprout/iterator/operation.hpp>
 #include <sprout/algorithm/fixed/result_of.hpp>
-#include <sprout/functional/dft/idft_element.hpp>
+#include <sprout/numeric/dft/idft_element.hpp>
 #include HDR_ITERATOR_SSCRISK_CEL_OR_SPROUT
 
 namespace sprout {
@@ -68,4 +68,4 @@ namespace sprout {
 	using sprout::fixed::idft;
 }	// namespace sprout
 
-#endif	// #ifndef SPROUT_FUNCTIONAL_DFT_FIXED_IDFT_HPP
+#endif	// #ifndef SPROUT_NUMERIC_DFT_FIXED_IDFT_HPP
diff --git a/sprout/numeric/dft/idft.hpp b/sprout/numeric/dft/idft.hpp
new file mode 100644
index 00000000..4b22f694
--- /dev/null
+++ b/sprout/numeric/dft/idft.hpp
@@ -0,0 +1,8 @@
+#ifndef SPROUT_NUMERIC_DFT_IDFT_HPP
+#define SPROUT_NUMERIC_DFT_IDFT_HPP
+
+#include <sprout/config.hpp>
+#include <sprout/numeric/dft/fixed/idft.hpp>
+#include <sprout/numeric/dft/fit/idft.hpp>
+
+#endif	// #ifndef SPROUT_NUMERIC_DFT_IDFT_HPP
diff --git a/sprout/functional/dft/idft_element.hpp b/sprout/numeric/dft/idft_element.hpp
similarity index 81%
rename from sprout/functional/dft/idft_element.hpp
rename to sprout/numeric/dft/idft_element.hpp
index 6994123a..4962b12e 100644
--- a/sprout/functional/dft/idft_element.hpp
+++ b/sprout/numeric/dft/idft_element.hpp
@@ -1,9 +1,9 @@
-#ifndef SPROUT_FUNCTIONAL_DFT_FIXED_IDFT_ELEMENT_HPP
-#define SPROUT_FUNCTIONAL_DFT_FIXED_IDFT_ELEMENT_HPP
+#ifndef SPROUT_NUMERIC_DFT_FIXED_IDFT_ELEMENT_HPP
+#define SPROUT_NUMERIC_DFT_FIXED_IDFT_ELEMENT_HPP
 
 #include <iterator>
 #include <sprout/config.hpp>
-#include <sprout/functional/dft/detail/dft_element_gen.hpp>
+#include <sprout/numeric/dft/detail/dft_element_gen.hpp>
 #include <sprout/math/constants.hpp>
 #include HDR_ITERATOR_SSCRISK_CEL_OR_SPROUT
 
@@ -47,4 +47,4 @@ namespace sprout {
 	}
 }	// namespace sprout
 
-#endif	// #ifndef SPROUT_FUNCTIONAL_DFT_FIXED_IDFT_ELEMENT_HPP
+#endif	// #ifndef SPROUT_NUMERIC_DFT_FIXED_IDFT_ELEMENT_HPP
diff --git a/sprout/numeric/fft.hpp b/sprout/numeric/fft.hpp
new file mode 100644
index 00000000..1ca74e43
--- /dev/null
+++ b/sprout/numeric/fft.hpp
@@ -0,0 +1,8 @@
+#ifndef SPROUT_NUMERIC_FFT_HPP
+#define SPROUT_NUMERIC_FFT_HPP
+
+#include <sprout/config.hpp>
+#include <sprout/numeric/fft/bitrev_table.hpp>
+
+#endif	// #ifndef SPROUT_NUMERIC_FFT_HPP
+
diff --git a/sprout/numeric/fft/bitrev_table.hpp b/sprout/numeric/fft/bitrev_table.hpp
new file mode 100644
index 00000000..3e65e230
--- /dev/null
+++ b/sprout/numeric/fft/bitrev_table.hpp
@@ -0,0 +1,8 @@
+#ifndef SPROUT_NUMERIC_FFT_BITREV_TABLE_HPP
+#define SPROUT_NUMERIC_FFT_BITREV_TABLE_HPP
+
+#include <sprout/config.hpp>
+#include <sprout/numeric/fft/fixed/bitrev_table.hpp>
+#include <sprout/numeric/fft/fit/bitrev_table.hpp>
+
+#endif	// #ifndef SPROUT_NUMERIC_FFT_BITREV_TABLE_HPP
diff --git a/sprout/functional/fft/fit/bitrev_table.hpp b/sprout/numeric/fft/fit/bitrev_table.hpp
similarity index 79%
rename from sprout/functional/fft/fit/bitrev_table.hpp
rename to sprout/numeric/fft/fit/bitrev_table.hpp
index 31f13117..56491c2f 100644
--- a/sprout/functional/fft/fit/bitrev_table.hpp
+++ b/sprout/numeric/fft/fit/bitrev_table.hpp
@@ -1,11 +1,11 @@
-#ifndef SPROUT_FUNCTIONAL_FFT_FIT_BITREV_TABLE_HPP
-#define SPROUT_FUNCTIONAL_FFT_FIT_BITREV_TABLE_HPP
+#ifndef SPROUT_NUMERIC_FFT_FIT_BITREV_TABLE_HPP
+#define SPROUT_NUMERIC_FFT_FIT_BITREV_TABLE_HPP
 
 #include <type_traits>
 #include <sprout/config.hpp>
 #include <sprout/container/traits.hpp>
 #include <sprout/container/functions.hpp>
-#include <sprout/functional/fft/fixed/bitrev_table.hpp>
+#include <sprout/numeric/fft/fixed/bitrev_table.hpp>
 #include <sprout/algorithm/fit/result_of.hpp>
 #include <sprout/sub_array.hpp>
 
@@ -38,4 +38,4 @@ namespace sprout {
 	}	// namespace fit
 }	// namespace sprout
 
-#endif	// #ifndef SPROUT_FUNCTIONAL_FFT_FIT_BITREV_TABLE_HPP
+#endif	// #ifndef SPROUT_NUMERIC_FFT_FIT_BITREV_TABLE_HPP
diff --git a/sprout/functional/fft/fixed/bitrev_table.hpp b/sprout/numeric/fft/fixed/bitrev_table.hpp
similarity index 88%
rename from sprout/functional/fft/fixed/bitrev_table.hpp
rename to sprout/numeric/fft/fixed/bitrev_table.hpp
index 7efce275..c545de70 100644
--- a/sprout/functional/fft/fixed/bitrev_table.hpp
+++ b/sprout/numeric/fft/fixed/bitrev_table.hpp
@@ -1,5 +1,5 @@
-#ifndef SPROUT_FUNCTIONAL_FFT_FIXED_BITREV_TABLE_HPP
-#define SPROUT_FUNCTIONAL_FFT_FIXED_BITREV_TABLE_HPP
+#ifndef SPROUT_NUMERIC_FFT_FIXED_BITREV_TABLE_HPP
+#define SPROUT_NUMERIC_FFT_FIXED_BITREV_TABLE_HPP
 
 #include <cstddef>
 #include <type_traits>
@@ -61,4 +61,4 @@ namespace sprout {
 	using sprout::fixed::bitrev_table;
 }	// namespace sprout
 
-#endif	// #ifndef SPROUT_FUNCTIONAL_FFT_FIXED_BITREV_TABLE_HPP
+#endif	// #ifndef SPROUT_NUMERIC_FFT_FIXED_BITREV_TABLE_HPP