Add GENERATE_COPY and GENERATE_VAR capturing generator macros

examples/311-Gen-CustomCapture.cpp

@@ -0,0 +1,41 @@
+// 311-Gen-CustomCapture.cpp
+// Shows how to provide custom capture list to the generator expression
+
+// Note that using variables inside generators is dangerous and should
+// be done only if you know what you are doing, because the generators
+// _WILL_ outlive the variables. Also, even if you know what you are
+// doing, you should probably use GENERATE_COPY or GENERATE_REF macros
+// instead. However, if your use case requires having a
+// per-variable custom capture list, this example shows how to achieve
+// that.
+
+#include <catch2/catch.hpp>
+
+TEST_CASE("Generate random doubles across different ranges",
+          "[generator][example][advanced]") {
+    // Workaround for old libstdc++
+    using record = std::tuple<double, double>;
+    // Set up 3 ranges to generate numbers from
+    auto r1 = GENERATE(table<double, double>({
+        record{3, 4},
+        record{-4, -3},
+        record{10, 1000}
+    }));
+
+    auto r2(r1);
+    
+    // This will take r1 by reference and r2 by value.
+    // Note that there are no advantages for doing so in this example,
+    // it is done only for expository purposes.
+    auto number = Catch::Generators::generate( CATCH_INTERNAL_LINEINFO,
+        [&r1, r2]{
+            using namespace Catch::Generators;
+            return makeGenerators(take(50, random(std::get<0>(r1), std::get<1>(r2))));
+        }
+    );
+
+    REQUIRE(std::abs(number) > 0);
+}
+
+// Compiling and running this file will result in 150 successful assertions
+