Function NormalizeExponentInFloatString

test/hex_float_test.cpp:464–483

Converts a floating point string so that the exponent prefix is 'e', and the exponent value does not have leading zeros. The Microsoft runtime library likes to write things like "2.5E+010". Convert that to "2.5e+10". We don't care what happens to strings that are not floating point strings.

// We don't care what happens to strings that are not floating point
// strings.
std::string NormalizeExponentInFloatString(std::string in) {
  std::string result;
  // Reserve one spot for the terminating null, even when the sscanf fails.
  std::vector<char> prefix(in.size() + 1);
  char e;
  char plus_or_minus;
  int exponent;  // in base 10
  if ((4 == std::sscanf(in.c_str(), "%[-+.0123456789]%c%c%d", prefix.data(), &e,
                        &plus_or_minus, &exponent)) &&
      (e == 'e' || e == 'E') &&
      (plus_or_minus == '-' || plus_or_minus == '+')) {
    // It looks like a floating point value with exponent.
    std::stringstream out;
    out << prefix.data() << 'e' << plus_or_minus << exponent;
    result = out.str();
  } else {
    result = in;
  }
  return result;
}

TEST(NormalizeFloat, Sample) {
  EXPECT_THAT(NormalizeExponentInFloatString(""), Eq(""));