refactor!: pow functions as detail

src/include/units/bits/pow.h

@@ -0,0 +1,61 @@
+// The MIT License (MIT)
+//
+// Copyright (c) 2018 Mateusz Pusz
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+#pragma once
+
+#include <cstdint>
+#include <cassert>
+
+namespace units::detail {
+
+constexpr std::intmax_t ipow10(std::intmax_t exp)
+{
+  assert(exp >= 0);
+  if (exp == 0) return 1;
+  std::intmax_t result = 1;
+  while (exp > 0) {
+    result *= 10;
+    --exp;
+  }
+  return result;
+}
+
+template<typename Rep>
+constexpr Rep fpow10(std::intmax_t exp)
+{
+  if (exp == 0) return Rep(1.0);
+  Rep result = Rep(1.0);
+  if (exp < 0) {
+    while (exp < 0) {
+      result = result / Rep(10.0);
+      ++exp;
+    }
+  } else {
+    while (exp > 0) {
+      result = result * Rep(10.0);
+      --exp;
+    }
+  }
+  return result;
+}
+
+}  // namespace units::detail