book: translate ch03

see #12

code/3/3.1.lambda.basic.cpp

@@ -0,0 +1,61 @@
+//
+// 3.1.lambda.basic.cpp
+// chapter 03 runtime enhancement
+// modern c++ tutorial
+//
+// created by changkun at changkun.de
+// https://github.com/changkun/modern-cpp-tutorial
+//
+
+
+#include <iostream>
+#include <utility>
+
+void lambda_value_capture() {
+    int value = 1;
+    auto copy_value = [value] {
+        return value;
+    };
+    value = 100;
+    auto stored_value = copy_value();
+    std::cout << "stored_value = " << stored_value << std::endl;
+    // At this moment, stored_value == 1, and value == 100.
+    // Because copy_value has copied when its was created.
+}
+
+void lambda_reference_capture() {
+    int value = 1;
+    auto copy_value = [&value] {
+        return value;
+    };
+    value = 100;
+    auto stored_value = copy_value();
+    std::cout << "stored_value = " << stored_value << std::endl;
+    // At this moment, stored_value == 100, value == 100.
+    // Because copy_value stores reference
+}
+
+void lambda_expression_capture() {
+    auto important = std::make_unique<int>(1);
+    auto add = [v1 = 1, v2 = std::move(important)](int x, int y) -> int {
+        return x+y+v1+(*v2);
+    };
+    std::cout << add(3,4) << std::endl;
+}
+
+void lambda_generic() {
+    auto generic = [](auto x, auto y) {
+        return x+y;
+    };
+    
+    std::cout << generic(1, 2) << std::endl;
+    std::cout << generic(1.1, 2.2) << std::endl;
+}
+
+int main() {
+    lambda_value_capture();
+    lambda_reference_capture();
+    lambda_expression_capture();
+    lambda_generic();
+    return 0;
+}