Trying to correct the documentation so that it actually describes how the code behaves. (Attempt two) (#712)

* Trying to correct the documentation so that it actually describes how the code behaves.

* tweaking the wording.

* Improving.

* Removing confusing sentence.

* Fixing formatting.

* Now with working example, tested.

* Added a smaller piece of code
This commit is contained in:
Daniel Lemire 2020-04-14 22:31:21 -04:00 committed by GitHub
parent b9ac0a79f1
commit 3c6ef83046
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3 changed files with 25 additions and 5 deletions

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@ -59,9 +59,17 @@ Once you have an element, you can navigate it with idiomatic C++ iterators, oper
* **Extracting Values:** You can cast a JSON element to a native type: `double(element)` or * **Extracting Values:** You can cast a JSON element to a native type: `double(element)` or
`double x = json_element`. This works for double, uint64_t, int64_t, bool, `double x = json_element`. This works for double, uint64_t, int64_t, bool,
dom::object and dom::array. You can also use is_*typename*()` to test if it is a dom::object and dom::array. An exception is thrown if the cast is not possible. You can also use is<*typename*>() to test if it is a
given type, and as_*typename*() to do the cast and return an error code on failure instead of an given type, or use the `type()` method: e.g., `element.type() == dom::element_type::DOUBLE`. Instead of casting, you can use get<*typename*>() to get the value: casts and get<*typename*>() can be used interchangeably. You can use a variant usage of get<*typename*>() with error codes to avoid exceptions: e.g.,
exception. ```c++
simdjson::error_code error;
double value; // variable where we store the value to be parsed
simdjson::padded_string numberstring = "1.2"_padded; // our JSON input ("1.2")
simdjson::dom::parser parser;
parser.parse(numberstring).get<double>().tie(value,error);
if (error) { std::cerr << error << std::endl; return EXIT_FAILURE; }
std::cout << "I parsed " << value << " from " << numberstring.data() << std::endl;
```
* **Field Access:** To get the value of the "foo" field in an object, use `object["foo"]`. * **Field Access:** To get the value of the "foo" field in an object, use `object["foo"]`.
* **Array Iteration:** To iterate through an array, use `for (auto value : array) { ... }`. If you * **Array Iteration:** To iterate through an array, use `for (auto value : array) { ... }`. If you
know the type of the value, you can cast it right there, too! `for (double value : array) { ... }` know the type of the value, you can cast it right there, too! `for (double value : array) { ... }`
@ -343,4 +351,3 @@ The parsed results (`dom::document`, `dom::element`, `array`, `object`) depend o
The CPU detection, which runs the first time parsing is attempted and switches to the fastest The CPU detection, which runs the first time parsing is attempted and switches to the fastest
parser for your CPU, is transparent and thread-safe. parser for your CPU, is transparent and thread-safe.

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@ -26,6 +26,7 @@ add_cpp_test(integer_tests integer_tests.cpp)
add_cpp_test(jsoncheck jsoncheck.cpp) add_cpp_test(jsoncheck jsoncheck.cpp)
add_cpp_test(parse_many_test parse_many_test.cpp) add_cpp_test(parse_many_test parse_many_test.cpp)
add_cpp_test(pointercheck pointercheck.cpp quicktests) add_cpp_test(pointercheck pointercheck.cpp quicktests)
add_cpp_test(extracting_values_example extracting_values_example.cpp quicktests)
set_property( set_property(
TEST basictests errortests integer_tests jsoncheck parse_many_test pointercheck TEST basictests errortests integer_tests jsoncheck parse_many_test pointercheck

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@ -0,0 +1,12 @@
#include <iostream>
#include "simdjson.h"
int main() {
simdjson::error_code error;
double value; // variable where we store the value to be parsed
simdjson::padded_string numberstring = "1.2"_padded; // our JSON input ("1.2")
simdjson::dom::parser parser;
parser.parse(numberstring).get<double>().tie(value,error);
if (error) { std::cerr << error << std::endl; return EXIT_FAILURE; }
std::cout << "I parsed " << value << " from " << numberstring.data() << std::endl;
}