rewrite std::exp to use std::pow

Slightly more readable.

Signed-off-by: Rosen Penev <[email protected]>

Author: neheb

src/canonmn_int.cpp

@@ -3053,7 +3053,7 @@ std::ostream& CanonMakerNote::printLe0x0000(std::ostream& os, const Value& value
 std::ostream& CanonMakerNote::printSi0x0001(std::ostream& os, const Value& value, const ExifData*) {
   std::ios::fmtflags f(os.flags());
   if (value.typeId() == unsignedShort && value.count() > 0) {
-    os << std::exp(canonEv(value.toInt64()) / 32 * std::log(2.0F)) * 100.0F;
+    os << std::pow(2.0F, canonEv(value.toInt64()) / 32) * 100.0F;
   }
   os.flags(f);
   return os;
@@ -3063,7 +3063,7 @@ std::ostream& CanonMakerNote::printSi0x0002(std::ostream& os, const Value& value
   std::ios::fmtflags f(os.flags());
   if (value.typeId() == unsignedShort && value.count() > 0) {
     // Ported from Exiftool by Will Stokes
-    os << std::exp(canonEv(value.toInt64()) * std::log(2.0F)) * 100.0F / 32.0F;
+    os << std::pow(2.0F, canonEv(value.toInt64())) * 100.0F / 32.0F;
   }
   os.flags(f);
   return os;

src/nikonmn_int.cpp

@@ -1759,7 +1759,7 @@ const TagInfo* Nikon3MakerNote::tagListLd4() {
 }
 
 std::ostream& Nikon3MakerNote::printIiIso(std::ostream& os, const Value& value, const ExifData*) {
-  auto v = std::lround(100.0 * std::exp((value.toInt64() / 12.0 - 5) * std::log(2.0)));
+  auto v = std::lround(100.0 * std::pow(2.0, value.toInt64() / 12.0 - 5));
   return os << v;
 }
 

src/tags_int.cpp

@@ -2593,7 +2593,7 @@ std::ostream& printBitmask(std::ostream& os, const Value& value, const ExifData*
 }
 
 float fnumber(float apertureValue) {
-  float result = std::exp(std::log(2.0F) * apertureValue / 2.F);
+  float result = std::pow(2.0F, apertureValue / 2.F);
   if (std::abs(result - 3.5) < 0.1) {
     result = 3.5;
   }
@@ -2602,7 +2602,7 @@ float fnumber(float apertureValue) {
 
 URational exposureTime(float shutterSpeedValue) {
   URational ur(1, 1);
-  const double tmp = std::exp(std::log(2.0) * static_cast<double>(shutterSpeedValue));
+  const double tmp = std::pow(2.0, shutterSpeedValue);
   if (tmp > 1) {
     const double x = std::round(tmp);
     // Check that x is within the range of a uint32_t before casting.