--- a/cpp/CMakeLists.txt	Fri Oct 20 12:36:51 2017 +0200
+++ b/cpp/CMakeLists.txt	Fri Oct 20 13:37:35 2017 +0200
@@ -16,5 +16,6 @@
 #
 
 add_subdirectory(executable)
+add_subdirectory(is_number)
 add_subdirectory(join)
 add_subdirectory(options)

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/cpp/is_number/CMakeLists.txt	Fri Oct 20 13:37:35 2017 +0200
@@ -0,0 +1,22 @@
+#
+# CMakeLists.txt -- code building for common code
+#
+# Copyright (c) 2013-2017 David Demelier <markand@malikania.fr>
+#
+# Permission to use, copy, modify, and/or distribute this software for any
+# purpose with or without fee is hereby granted, provided that the above
+# copyright notice and this permission notice appear in all copies.
+#
+# THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+# OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+#
+
+code_define_module(
+    NAME is-number
+    SOURCES is_number.hpp
+)

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/cpp/is_number/is_number.hpp	Fri Oct 20 13:37:35 2017 +0200
@@ -0,0 +1,73 @@
+/*
+ * is_number.hpp -- check if string is a number
+ *
+ * Copyright (c) 2016-2017 David Demelier <markand@malikania.fr>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#ifndef IS_NUMBER_HPP
+#define IS_NUMBER_HPP
+
+#include <cstdlib>
+#include <string>
+
+/**
+ * Check if the string is an integer.
+ *
+ * \param value the input
+ * \param base the optional base
+ * \return true if integer
+ */
+inline bool is_int(const std::string& str, int base = 10) noexcept
+{
+    if (str.empty())
+        return false;
+
+    char* ptr;
+
+    std::strtol(str.c_str(), &ptr, base);
+
+    return *ptr == 0;
+}
+
+/**
+ * Check if the string is real.
+ *
+ * \param value the value
+ * \return true if real
+ */
+inline bool is_real(const std::string &str) noexcept
+{
+    if (str.empty())
+        return false;
+
+    char* ptr;
+
+    std::strtod(str.c_str(), &ptr);
+
+    return *ptr == 0;
+}
+
+/**
+ * Check if the string is a number.
+ *
+ * \param value the value
+ * \return true if it is a number
+ */
+inline bool is_number(const std::string& str) noexcept
+{
+    return is_int(str) || is_real(str);
+}
+
+#endif // !IS_NUMBER_HPP

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/cpp/is_number/test/main.cpp	Fri Oct 20 13:37:35 2017 +0200
@@ -0,0 +1,53 @@
+/*
+ * main.cpp -- test is_number functions
+ *
+ * Copyright (c) 2013-2017 David Demelier <markand@malikania.fr>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#define BOOST_TEST_MODULE "is-number"
+#include <boost/test/unit_test.hpp>
+
+#include "is_number.hpp"
+
+BOOST_AUTO_TEST_CASE(simple_is_int)
+{
+    BOOST_TEST(is_int("123"));
+    BOOST_TEST(is_int("-126"));
+    BOOST_TEST(!is_int(""));
+    BOOST_TEST(!is_int("bdf"));
+    BOOST_TEST(!is_int("false"));
+}
+
+BOOST_AUTO_TEST_CASE(simple_is_real)
+{
+    BOOST_TEST(is_real("123"));
+    BOOST_TEST(is_real("-126"));
+    BOOST_TEST(is_real("56.28"));
+    BOOST_TEST(is_real("1e5"));
+    BOOST_TEST(!is_real(""));
+    BOOST_TEST(!is_real("bdf"));
+    BOOST_TEST(!is_real("false"));
+}
+
+BOOST_AUTO_TEST_CASE(simple_is_number)
+{
+    BOOST_TEST(is_number("123"));
+    BOOST_TEST(is_number("-126"));
+    BOOST_TEST(is_number("56.28"));
+    BOOST_TEST(is_number("1e5"));
+    BOOST_TEST(!is_number(""));
+    BOOST_TEST(!is_number("bdf"));
+    BOOST_TEST(!is_number("false"));
+}