Another example. (simdjson#790)

lemire · web-flow · commit f397b6fedfc9 · 2020-04-23T21:48:41.000-04:00
* Another example.

* Adding a reference to error chaining.
diff --git a/doc/basics.md b/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:
diff --git a/tests/readme_examples.cpp b/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;
 }
diff --git a/tests/readme_examples_noexceptions.cpp b/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;
 }

Original file line number	Diff line number	Diff line change
`@@ -84,6 +84,13 @@ void basics_dom_3() {`
`84`	`84`	`}`
`85`	`85`	`}`
`86`	`86`
	`87`	`+void basics_dom_4() {`
	`88`	`+ auto abstract_json = R"(`
	`89`	`+ { "str" : { "123" : {"abc" : 3.14 } } } )"_padded;`
	`90`	`+ dom::parser parser;`
	`91`	`+ double v = parser.parse(abstract_json)["str"]["123"]["abc"].get<double>();`
	`92`	`+ cout << "number: " << v << endl;`
	`93`	`+}`
`87`	`94`
`88`	`95`
`89`	`96`	`namespace treewalk_1 {`
`@@ -236,5 +243,6 @@ int main() {`
`236`	`243`	`basics_dom_1();`
`237`	`244`	`basics_dom_2();`
`238`	`245`	`basics_dom_3();`
	`246`	`+ basics_dom_4();`
`239`	`247`	`return 0;`
`240`	`248`	`}`
Original file line number	Diff line number	Diff line change
`@@ -77,6 +77,8 @@ void basics_error_3() {`
`77`	`77`	`}`
`78`	`78`	`}`
`79`	`79`	`}`
	`80`	`+`
	`81`	`+`
`80`	`82`	`void basics_error_4() {`
`81`	`83`	`auto abstract_json = R"( [`
`82`	`84`	`{ "12345" : {"a":12.34, "b":56.78, "c": 9998877} },`
`@@ -117,6 +119,17 @@ void basics_error_4() {`
`117`	`119`	`}`
`118`	`120`	`}`
`119`	`121`
	`122`	`+void basics_error_5() {`
	`123`	`+ auto abstract_json = R"(`
	`124`	`+ { "str" : { "123" : {"abc" : 3.14 } } } )"_padded;`
	`125`	`+ dom::parser parser;`
	`126`	`+ double v;`
	`127`	`+ simdjson::error_code error;`
	`128`	`+ parser.parse(abstract_json)["str"]["123"]["abc"].get<double>().tie(v, error);`
	`129`	`+ if (error) { cerr << error << endl; exit(1); }`
	`130`	`+ cout << "number: " << v << endl;`
	`131`	`+}`
	`132`	`+`
`120`	`133`
`121`	`134`	`#ifdef SIMDJSON_CPLUSPLUS17`
`122`	`135`	`void basics_error_3_cpp17() {`
`@@ -174,5 +187,6 @@ int main() {`
`174`	`187`	`basics_error_2();`
`175`	`188`	`basics_error_3();`
`176`	`189`	`basics_error_4();`
	`190`	`+ basics_error_5();`
`177`	`191`	`return 0;`
`178`	`192`	`}`