added doc to README and examples

Author: toughengineer

README.md

@@ -401,6 +401,23 @@ except `fast_float::integer_times_pow10()` does not report out-of-range errors,
 underflows to zero or overflows to infinity when the resulting value is
 out of range.
 
+You can use template overloads to get the result converted to different
+supported floating-point types: `float`, `double`, etc.
+For example, to get result as `float` use
+`fast_float::integer_times_pow10<float>()` specialization:
+```C++
+const uint64_t W = 1234567;
+const int Q = 23;
+const double result = fast_float::integer_times_pow10<float>(W, Q);
+std::cout.precision(7);
+std::cout << "float: " << W << " * 10^" << Q << " = " << result << " ("
+          << (result == 1234567e23f ? "==" : "!=") << "expected)\n";
+```
+outputs
+```
+float: 1234567 * 10^23 = 1.234567e+29 (==expected)
+```
+
 Overloads of `fast_float::integer_times_pow10()` are provided for
 signed and unsigned integer types: `int64_t`, `uint64_t`, etc.
 

tests/example_integer_times_pow10.cpp

@@ -2,11 +2,35 @@
 
 #include <iostream>
 
-int main() {
+void default_overload() {
   const uint64_t W = 12345678901234567;
   const int Q = 23;
   const double result = fast_float::integer_times_pow10(W, Q);
   std::cout.precision(17);
   std::cout << W << " * 10^" << Q << " = " << result << " ("
             << (result == 12345678901234567e23 ? "==" : "!=") << "expected)\n";
 }
+
+void double_specialization() {
+  const uint64_t W = 12345678901234567;
+  const int Q = 23;
+  const double result = fast_float::integer_times_pow10<double>(W, Q);
+  std::cout.precision(17);
+  std::cout << "double: " << W << " * 10^" << Q << " = " << result << " ("
+            << (result == 12345678901234567e23 ? "==" : "!=") << "expected)\n";
+}
+
+void float_specialization() {
+  const uint64_t W = 1234567;
+  const int Q = 23;
+  const double result = fast_float::integer_times_pow10<float>(W, Q);
+  std::cout.precision(7);
+  std::cout << "float: " << W << " * 10^" << Q << " = " << result << " ("
+            << (result == 1234567e23f ? "==" : "!=") << "expected)\n";
+}
+
+int main() {
+  default_overload();
+  double_specialization();
+  float_specialization();
+}