Better conversion from string to int

include/cif++/item.hpp

@@ -459,9 +459,14 @@ struct item_handle::item_value_as<T, std::enable_if_t<std::is_arithmetic_v<T> an
 		{
 			auto txt = ref.text();
 
-			std::from_chars_result r = selected_charconv<value_type>::from_chars(txt.data(), txt.data() + txt.size(), result);
+			auto b = txt.data();
+			auto e = txt.data() + txt.size();
 
-			if (r.ec != std::errc())
+			std::from_chars_result r = (b + 1 < e and *b == '+' and std::isdigit(b[1])) ?
+				selected_charconv<value_type>::from_chars(b + 1, e, result) :
+				selected_charconv<value_type>::from_chars(b, e, result);
+
+			if (r.ec != std::errc() or r.ptr != e)
 			{
 				result = {};
 				if (cif::VERBOSE)
@@ -470,6 +475,8 @@ struct item_handle::item_value_as<T, std::enable_if_t<std::is_arithmetic_v<T> an
 						std::cerr << "Attempt to convert " << std::quoted(txt) << " into a number\n";
 					else if (r.ec == std::errc::result_out_of_range)
 						std::cerr << "Conversion of " << std::quoted(txt) << " into a type that is too small\n";
+					else
+						std::cerr << "Not a valid number " << std::quoted(txt) << '\n';
 				}
 			}
 		}
@@ -489,9 +496,14 @@ struct item_handle::item_value_as<T, std::enable_if_t<std::is_arithmetic_v<T> an
 		{
 			value_type v = {};
 
-			std::from_chars_result r = selected_charconv<value_type>::from_chars(txt.data(), txt.data() + txt.size(), v);
+			auto b = txt.data();
+			auto e = txt.data() + txt.size();
+
+			std::from_chars_result r = (b + 1 < e and *b == '+' and std::isdigit(b[1])) ?
+				selected_charconv<value_type>::from_chars(b + 1, e, v) :
+				selected_charconv<value_type>::from_chars(b, e, v);
 
-			if (r.ec != std::errc())
+			if (r.ec != std::errc() or r.ptr != e)
 			{
 				if (cif::VERBOSE)
 				{
@@ -499,6 +511,8 @@ struct item_handle::item_value_as<T, std::enable_if_t<std::is_arithmetic_v<T> an
 						std::cerr << "Attempt to convert " << std::quoted(txt) << " into a number\n";
 					else if (r.ec == std::errc::result_out_of_range)
 						std::cerr << "Conversion of " << std::quoted(txt) << " into a type that is too small\n";
+					else
+						std::cerr << "Not a valid number " << std::quoted(txt) << '\n';
 				}
 				result = 1;
 			}

test/unit-v2-test.cpp

@@ -150,6 +150,31 @@ BOOST_AUTO_TEST_CASE(cc_2)
 	}
 }
 
+BOOST_AUTO_TEST_CASE(cc_3)
+{
+	cif::category c("foo");
+	c.emplace({
+		{ "f-1", 1 },
+		{ "f-2", "-1" },
+		{ "f-3", "+1" },
+		{ "f-4", " 1" },
+		{ "f-5", " +1" },
+		{ "f-6", "1 " },
+	});
+
+	auto row = c.front();
+	BOOST_CHECK_EQUAL(row["f-1"].as<int>(), 1);
+	BOOST_CHECK_EQUAL(row["f-2"].as<int>(), -1);
+	BOOST_CHECK_EQUAL(row["f-3"].as<int>(), 1);
+
+	// BOOST_CHECK_THROW(row["f-4"].as<int>(), std::exception);
+	// BOOST_CHECK_THROW(row["f-5"].as<int>(), std::exception);
+	// BOOST_CHECK_THROW(row["f-6"].as<int>(), std::exception);
+	BOOST_CHECK_EQUAL(row["f-4"].as<int>(), 0);
+	BOOST_CHECK_EQUAL(row["f-5"].as<int>(), 0);
+	BOOST_CHECK_EQUAL(row["f-6"].as<int>(), 0);
+}
+
 BOOST_AUTO_TEST_CASE(item_1)
 {
 	using namespace cif;