Another example. (#790)

* Another example.

* Adding a reference to error chaining.

doc/basics.md

@@ -145,6 +145,18 @@ for (dom::object obj : parser.parse(abstract_json)) {
 }
 ```
 
+And another one:
+
+
+```C++
+  auto abstract_json = R"(
+    {  "str" : { "123" : {"abc" : 3.14 } } } )"_padded;
+  dom::parser parser;
+  double v = parser.parse(abstract_json)["str"]["123"]["abc"].get<double>();
+  cout << "number: " << v << endl;
+```
+
+
 C++17 Support
 -------------
 
@@ -341,6 +353,21 @@ for (dom::element elem : rootarray) {
 
 ```
 
+And another one:
+
+```C++
+  auto abstract_json = R"(
+    {  "str" : { "123" : {"abc" : 3.14 } } } )"_padded;
+  dom::parser parser;
+  double v;
+  simdjson::error_code error;
+  parser.parse(abstract_json)["str"]["123"]["abc"].get<double>().tie(v, error);
+  if (error) { cerr << error << endl; exit(1); }
+  cout << "number: " << v << endl;
+```
+
+Notice how we can string several operation (`parser.parse(abstract_json)["str"]["123"]["abc"].get<double>()`) and only check for the error once, a strategy we call  *error chaining*.
+
 ### Exceptions
 
 Users more comfortable with an exception flow may choose to directly cast the `simdjson_result<T>` to the desired type:

tests/readme_examples.cpp

@@ -84,6 +84,13 @@ void basics_dom_3() {
   }
 }
 
+void basics_dom_4() {
+  auto abstract_json = R"(
+    {  "str" : { "123" : {"abc" : 3.14 } } } )"_padded;
+  dom::parser parser;
+  double v = parser.parse(abstract_json)["str"]["123"]["abc"].get<double>();
+  cout << "number: " << v << endl;
+}
 
 
 namespace treewalk_1 {
@@ -236,5 +243,6 @@ int main() {
   basics_dom_1();
   basics_dom_2();
   basics_dom_3();
+  basics_dom_4();
   return 0;
 }

tests/readme_examples_noexceptions.cpp

@@ -77,6 +77,8 @@ void basics_error_3() {
     }
   }
 }
+
+
 void basics_error_4() {
   auto abstract_json = R"( [
     {  "12345" : {"a":12.34, "b":56.78, "c": 9998877}   },
@@ -117,6 +119,17 @@ void basics_error_4() {
   }
 }
 
+void basics_error_5() {
+  auto abstract_json = R"(
+    {  "str" : { "123" : {"abc" : 3.14 } } } )"_padded;
+  dom::parser parser;
+  double v;
+  simdjson::error_code error;
+  parser.parse(abstract_json)["str"]["123"]["abc"].get<double>().tie(v, error);
+  if (error) { cerr << error << endl; exit(1); }
+  cout << "number: " << v << endl;
+}
+
 
 #ifdef SIMDJSON_CPLUSPLUS17
 void basics_error_3_cpp17() {
@@ -174,5 +187,6 @@ int main() {
   basics_error_2();
   basics_error_3();
   basics_error_4();
+  basics_error_5();
   return 0;
 }