From cc35b618802437c4ca1f4a6e65ba868b7ed98a6d Mon Sep 17 00:00:00 2001
From: Sam Yates <halfflat@gmail.com>
Date: Fri, 12 Aug 2016 17:42:15 +0200
Subject: [PATCH] Add 'nop_function' helper for trivial functions.
---
src/util/nop.hpp | 29 +++++++++++++++
tests/unit/CMakeLists.txt | 1 +
tests/unit/test_nop.cpp | 75 +++++++++++++++++++++++++++++++++++++++
3 files changed, 105 insertions(+)
create mode 100644 src/util/nop.hpp
create mode 100644 tests/unit/test_nop.cpp
diff --git a/src/util/nop.hpp b/src/util/nop.hpp
new file mode 100644
index 00000000..8315e93f
--- /dev/null
+++ b/src/util/nop.hpp
@@ -0,0 +1,29 @@
+#pragma once
+
+/*
+ * Provide object that implicitly converts to
+ * a std::function object that does nothing but return a
+ * default-constructed type or void.
+ */
+
+#include <functional>
+
+namespace nest {
+namespace mc {
+namespace util {
+
+static struct nop_function_t {
+ template <typename R, typename... Args>
+ operator std::function<R (Args...)>() const {
+ return [](Args...) { return R{}; };
+ }
+
+ template <typename... Args>
+ operator std::function<void (Args...)>() const {
+ return [](Args...) { };
+ }
+} nop_function;
+
+} // namespace util
+} // namespace mc
+} // namespace nest
diff --git a/tests/unit/CMakeLists.txt b/tests/unit/CMakeLists.txt
index fb1b9369..83c537b2 100644
--- a/tests/unit/CMakeLists.txt
+++ b/tests/unit/CMakeLists.txt
@@ -21,6 +21,7 @@ set(TEST_SOURCES
test_mask_stream.cpp
test_matrix.cpp
test_mechanisms.cpp
+ test_nop.cpp
test_optional.cpp
test_parameters.cpp
test_point.cpp
diff --git a/tests/unit/test_nop.cpp b/tests/unit/test_nop.cpp
new file mode 100644
index 00000000..cf131d9e
--- /dev/null
+++ b/tests/unit/test_nop.cpp
@@ -0,0 +1,75 @@
+#include "gtest.h"
+#include "util/nop.hpp"
+
+using namespace nest::mc::util;
+
+TEST(nop,void_fn) {
+ std::function<void ()> f{nop_function};
+
+ EXPECT_TRUE(f);
+ f(); // should do nothing
+
+ bool flag = false;
+ f = [&]() { flag = true; };
+ f();
+ EXPECT_TRUE(flag);
+
+ flag = false;
+ f = nop_function;
+ f();
+ EXPECT_FALSE(flag);
+
+ // with some arguments
+ std::function<void (int, int)> g{nop_function};
+ EXPECT_TRUE(g);
+ g(2, 3); // should do nothing
+
+ int sum = 0;
+ g = [&](int a, int b) { sum = a+b; };
+ g(2, 3);
+ EXPECT_EQ(5, sum);
+
+ sum = 0;
+ g = nop_function;
+ g(2, 3);
+ EXPECT_EQ(0, sum);
+}
+
+struct check_default {
+ int value = 100;
+
+ check_default() = default;
+ explicit check_default(int n): value(n) {}
+};
+
+TEST(nop,default_return_fn) {
+ std::function<check_default ()> f{nop_function};
+
+ EXPECT_TRUE(f);
+ auto result = f();
+ EXPECT_EQ(result.value, 100);
+
+ f = []() { return check_default(17); };
+ result = f();
+ EXPECT_EQ(result.value, 17);
+
+ f = nop_function;
+ result = f();
+ EXPECT_EQ(result.value, 100);
+
+ std::function<check_default (double, double)> g{nop_function};
+
+ EXPECT_TRUE(g);
+ result = g(1.4, 1.5);
+ EXPECT_EQ(result.value, 100);
+
+ g = [](double x, double y) { return check_default{(int)(x*y)}; };
+ result = g(1.4, 1.5);
+ EXPECT_EQ(result.value, 2);
+
+ g = nop_function;
+ result = g(1.4, 1.5);
+ EXPECT_EQ(result.value, 100);
+
+}
+
--
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