updating documentation

Author: lemire

README.md

@@ -57,6 +57,7 @@ Example:
 ```C++
 #include "fast_float/fast_float.h"
 #include <iostream>
+#include <string>
 
 int main() {
   std::string input = "3.1416 xyz ";
@@ -68,6 +69,25 @@ int main() {
 }
 ```
 
+Though the C++17 standard has you do a comparison with `std::errc()` to check whether the conversion worked, you can avoid it by casting the result to a `bool` like so:
+
+```cpp
+#include "fast_float/fast_float.h"
+#include <iostream>
+#include <string>
+
+int main() {
+  std::string input = "3.1416 xyz ";
+  double result;
+  if(auto answer = fast_float::from_chars(input.data(), input.data() + input.size(), result)) {
+    std::cout << "parsed the number " << result << std::endl;
+    return EXIT_SUCCESS;
+  }
+  std::cerr << "failed to parse " << result << std::endl;
+  return EXIT_FAILURE;
+}
+```
+
 You can parse delimited numbers:
 
 ```C++