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Merge pull request #160 from ros2/function-traits-return-type

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Added support for deducing the return type of a functor
This commit is contained in:
Esteve Fernandez 2015-11-23 15:02:22 -08:00
commit 82d895c749
2 changed files with 88 additions and 1 deletions
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4
rclcpp/include/rclcpp/function_traits.hpp
View file

@ -54,6 +54,8 @@ struct function_traits
template<std::size_t N>
using argument_type = typename std::tuple_element<N, arguments>::type;
using return_type = typename function_traits<decltype( & FunctionT::operator())>::return_type;
};
// Free functions
@ -66,6 +68,8 @@ struct function_traits<ReturnTypeT(Args ...)>
template<std::size_t N>
using argument_type = typename std::tuple_element<N, arguments>::type;
using return_type = ReturnTypeT;
};
// Function pointers

85
rclcpp/test/test_function_traits.cpp
View file

@ -14,7 +14,9 @@
#include <gtest/gtest.h>
#include <rclcpp/function_traits.hpp>
#include <string>
#include "rclcpp/function_traits.hpp"
int func_no_args()
{
@ -118,6 +120,42 @@ int func_accept_callback(FunctorT callback)
return callback(a, b);
}
template<
typename FunctorT,
std::size_t Arity = 0,
typename std::enable_if<
rclcpp::function_traits::arity_comparator<Arity, FunctorT>::value
>::type * = nullptr,
typename std::enable_if<
std::is_same<
typename rclcpp::function_traits::function_traits<FunctorT>::return_type,
double
>::value
>::type * = nullptr
>
double func_accept_callback_return_type(FunctorT callback)
{
return callback();
}
template<
typename FunctorT,
std::size_t Arity = 0,
typename std::enable_if<
rclcpp::function_traits::arity_comparator<Arity, FunctorT>::value
>::type * = nullptr,
typename std::enable_if<
std::is_same<
typename rclcpp::function_traits::function_traits<FunctorT>::return_type,
std::string
>::value
>::type * = nullptr
>
std::string func_accept_callback_return_type(FunctorT callback)
{
return callback();
}
/*
Tests that funcion_traits calculates arity of several functors.
*/
@ -452,6 +490,39 @@ TEST(TestFunctionTraits, same_arguments) {
"Functor and lambda have the same arguments");
}
TEST(TestFunctionTraits, return_type) {
// Test regular function
static_assert(
std::is_same<
rclcpp::function_traits::function_traits<decltype(func_no_args)>::return_type,
int
>::value,
"Functor return ints");
// Test lambda
auto lambda_one_int_return_double = [](int one) -> double {
(void)one;
return 1.0;
};
static_assert(
std::is_same<
rclcpp::function_traits::function_traits<
decltype(lambda_one_int_return_double)
>::return_type,
double
>::value,
"Lambda returns a double");
// Test objects that have a call operator
static_assert(
std::is_same<
rclcpp::function_traits::function_traits<FunctionObjectNoArgs>::return_type,
int
>::value,
"Functor return ints");
}
/*
Tests that functions are matched via SFINAE.
*/
@ -500,4 +571,16 @@ TEST(TestFunctionTraits, sfinae_match) {
EXPECT_EQ(2, func_accept_callback(FunctionObjectTwoInts()));
EXPECT_EQ(3, func_accept_callback(FunctionObjectOneIntOneChar()));
auto lambda_no_args_double = []() -> double {
return 123.45;
};
auto lambda_no_args_string = []() -> std::string {
return std::string("foo");
};
EXPECT_EQ(123.45, func_accept_callback_return_type(lambda_no_args_double));
EXPECT_EQ("foo", func_accept_callback_return_type(lambda_no_args_string));
}