New upstream version 8.1.0

thirdparty/source/nu/tests/error_or_example.cpp

@@ -0,0 +1,38 @@
+using nu::error_or;
+using nu::make_error_or;
+
+// default-constructed objects contain Err(), which by default is std::error_code
+error_or<int> e;
+error_or<int> i(1);
+
+// et will still contain Err()
+error_or<int> et = e / [] (int i) { return i+1; };
+ASSERT_EQ(et.error(), std::error_code());
+
+// it will contain 2
+error_or<int> it = i / [] (int i) { return i+1; };
+ASSERT_EQ(it.value(), 2);
+
+// er will be set to -1
+int er = e.reduce(
+    [] (int i) { return i; },
+    [] (std::error_code) { return -1; });
+ASSERT_EQ(er, -1);
+
+// ir will be set to 1
+int ir = i.reduce(
+    [] (int i) { return i; },
+    [] (std::error_code) { return -1; });
+ASSERT_EQ(ir, 1);
+
+// % can be used to chain operations that may themselves fail
+error_or<double> d =
+    make_error_or<int>(1)
+    / [] (int i) { return i - 1; }
+    % [] (int i) -> error_or<double> {
+        if (i != 0)
+            return i * 3.14;
+        else
+            return {std::make_error_code(std::errc::invalid_argument)};
+    };
+ASSERT_FALSE(d);