Style (normalize power implementations).

Author: evoskuil

include/bitcoin/system/impl/math/power.ipp

@@ -33,6 +33,7 @@ namespace system {
 
 // Called by bc::base85 (for number coding).
 // Called by wallet::electrum_v1 (for number coding).
+// Overflow is allowed behavior as this models a mathematical operator.
 template <typename Value, typename Base, typename Exponent,
     if_integer<Value> = true,
     if_integer<Base> = true,
@@ -42,19 +43,11 @@ constexpr Value power_(Base base, Exponent exponent) NOEXCEPT
     if (is_power_overflow(base, exponent))
         return 0;
 
-    if (is_zero(exponent))
-        return 1;
-
-    auto value = possible_narrow_and_sign_cast<Value>(base);
-
-    // Overflow is allowed behavior as this models a mathematical operator.
-    BC_PUSH_WARNING(NARROWING_CONVERSION)
-    BC_PUSH_WARNING(SIZE_NARROWING_CONVERSION)
-    while (--exponent > 0u) { value *= base; }
-    BC_POP_WARNING()
-    BC_POP_WARNING()
+    Value product{ 1 };
+    while (exponent-- > 0u)
+        product *= possible_narrow_and_sign_cast<Value>(base);
 
-    return value;
+    return product;
 }
 
 // published

test/math/power.cpp

@@ -37,23 +37,21 @@ static_assert(power(3,   0u) == 1u);
 static_assert(power(3u,  0u) == 1u);
 static_assert(power(3,  10u) == 0xe6a9_size);
 static_assert(power(3u, 10u) == 0xe6a9_size);
-static_assert(power<uint16_t>(3, 11u) == 0xb3fb_u16);
 
 static_assert(power(-1, 0u) == 1u);
 static_assert(power(-1, 1u) == 1_nsize);
 
 static_assert(power(-3,  0u) == 1u);
 static_assert(power(-3,  1u) == 3_nsize);
 static_assert(power(-3, 10u) == 0xe6a9_size);
-static_assert(power<uint16_t>(-3, 11u) == 0x4c05_u16);
 
 // power2
 static_assert(power2(0u) == 1u);
 static_assert(power2(0u) == 1u);
 static_assert(power2(1u) == 2u);
 static_assert(power2(1u) == 2u);
 static_assert(power2<uint16_t>(15u) == 0b1000'0000'0000'0000_u16);
-static_assert(power2<uint16_t>(16u) == 0_u16);
+static_assert(power2<uint16_t>(16u) == 0_u16); // overflow
 
 // power<>
 static_assert(power<0>(16u) == power(0u, 16u));