Add forward_iterable concept example

Author: gammasoft71

examples/xtd.core.examples/README.md

@@ -50,6 +50,7 @@
 
 * [comparable](concepts/comparable/README.md) shows how to use how to use [xtd::comparable](https://gammasoft71.github.io/xtd/reference_guides/latest/classxtd_1_1comparable.html) concept.
 * [enumerable](concepts/enumerable/README.md) shows how to use how to use [xtd::collections::generic::enumerable](https://gammasoft71.github.io/xtd/reference_guides/latest/classxtd_1_1collections_1_1generic_1_1enumerable.html) concept.
+* [forward_iterable](concepts/forward_iterable/README.md) shows how to use how to use [xtd:: forward_iterable](https://gammasoft71.github.io/xtd/reference_guides/latest/classxtd_1_1 forward__iterable.html) concept.
 * [stringable](concepts/stringable/README.md) shows how to use how to use [xtd::stringable](https://gammasoft71.github.io/xtd/reference_guides/latest/classxtd_1_1stringable.html) concept.
 
 ## [Configuration](configuration/README.md)

examples/xtd.core.examples/concepts/CMakeLists.txt

@@ -6,6 +6,7 @@ find_package(xtd REQUIRED)
 add_projects(
   comparable
   enumerable
+  forward_iterable
   stringable
 )
 

examples/xtd.core.examples/concepts/README.md

@@ -4,6 +4,7 @@
 
 * [comparable](comparable/README.md) shows how to use how to use [xtd::comparable](https://gammasoft71.github.io/xtd/reference_guides/latest/classxtd_1_1comparable.html) concept.
 * [enumerable](enumerable/README.md) shows how to use how to use [xtd::collections::generic::enumerable](https://gammasoft71.github.io/xtd/reference_guides/latest/classxtd_1_1collections_1_1generic_1_1enumerable.html) concept.
+* [forward_iterable](forward_iterable/README.md) shows how to use how to use [xtd:: forward_iterable](https://gammasoft71.github.io/xtd/reference_guides/latest/classxtd_1_1 forward__iterable.html) concept.
 * [stringable](stringable/README.md) shows how to use how to use [xtd::stringable](https://gammasoft71.github.io/xtd/reference_guides/latest/classxtd_1_1stringable.html) concept.
 
 ## Build and run any project

examples/xtd.core.examples/concepts/forward_iterable/CMakeLists.txt

@@ -0,0 +1,6 @@
+cmake_minimum_required(VERSION 3.20)
+
+project(forward_iterable)
+find_package(xtd REQUIRED)
+add_sources(README.md src/forward_iterable.cpp)
+target_type(CONSOLE_APPLICATION)

examples/xtd.core.examples/concepts/forward_iterable/README.md

@@ -0,0 +1,36 @@
+# enumerable
+
+Shows how to use [xtd::collections::generic::enumerable](https://gammasoft71.github.io/xtd/reference_guides/latest/classxtd_1_1collections_1_1generic_1_1enumerable.html) concept.
+
+## Sources
+
+* [src/enumerable.cpp](src/enumerable.cpp)
+* [CMakeLists.txt](CMakeLists.txt)
+
+## Build and run
+
+Open "Command Prompt" or "Terminal". Navigate to the folder that contains the project and type the following:
+
+```cmake
+xtdc run
+```
+
+## Output
+
+```
+ 2
+ 4
+ 6
+ 8
+10
+18
+21
+24
+27
+30
+44
+48
+52
+56
+60
+```

examples/xtd.core.examples/concepts/forward_iterable/src/forward_iterable.cpp

@@ -0,0 +1,42 @@
+#include <xtd/xtd>
+
+auto int_generator() -> enumerable_generator<int> {
+  co_yield 15;
+  co_yield 11;
+  co_yield 13;
+  co_yield 14;
+  co_yield 12;
+}
+
+template <forward_iterable forward_iterable_type>
+[[nodiscard]] auto from_forward_iterable(forward_iterable_type&& iterable) -> enumerable_generator<forward_iterable_value_type<forward_iterable_type>> {
+  for (const auto& item : iterable)
+    co_yield item;
+}
+
+auto main() -> int {
+  for (auto item : from_forward_iterable(std::vector {5, 1, 3, 4, 2}).select([](auto v) {return v * 2;}).order())
+    println("{,2}", item);
+  for (auto item : from_forward_iterable(list {10, 6, 8, 9, 7}).select([](auto v) {return v * 3;}).order())
+    println("{,2}", item);
+  for (auto item : from_forward_iterable(int_generator()).select([](auto v) {return v * 4;}).order())
+    println("{,2}", item);
+}
+
+// This code produces the following output :
+//
+//  2
+//  4
+//  6
+//  8
+// 10
+// 18
+// 21
+// 24
+// 27
+// 30
+// 44
+// 48
+// 52
+// 56
+// 60