reduce requirements for c++ compliance

configure

@@ -3919,60 +3919,6 @@ ac_config_headers="$ac_config_headers include/cif++/Config.hpp"
 
 
 
-
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking compiler standards compliance" >&5
-$as_echo_n "checking compiler standards compliance... " >&6; }
-cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-#include <algorithm>
-
-
-
-template<typename COMP>
-
-class foo
-
-{
-
-public:
-
-foo(int a, COMP&& b)
-
-: m_a(a), m_b(std::move(b)) {}
-
-
-
-int m_a;
-
-COMP m_b;
-
-};
-
-
-
-void bar(const int& b)
-
-{
-
-int c = 1;
-
-auto f = new foo(c, [tag = c, b](const int& x)
-
-{ x < b; });
-
-}
-
-
-_ACEOF
-if ac_fn_cxx_try_compile "$LINENO"; then :
-
-else
-  as_fn_error $? "Your c++ compiler is not capable of compiling libcifpp, please upgrade" "$LINENO" 5
-fi
-rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: \"ok\"" >&5
-$as_echo "\"ok\"" >&6; }
-
 # Find a good install program.  We prefer a C program (faster),
 # so one script is as good as another.  But avoid the broken or
 # incompatible versions:

configure.ac

@@ -15,14 +15,14 @@ AC_CONFIG_HEADERS([include/cif++/Config.hpp])
 
 AC_PREFIX_DEFAULT(/usr/local)
 
-AC_DEFUN([read_test], [AC_LANG_SOURCE(
-	esyscmd(tools/m4esc.sh config-tests/$1))])
-
-AC_MSG_CHECKING([compiler standards compliance])
-AC_COMPILE_IFELSE(
-	[read_test(cpp-17-test.cpp)], [],
-	[AC_MSG_ERROR([Your c++ compiler is not capable of compiling libcifpp, please upgrade])])
-AC_MSG_RESULT(ok)
+dnl AC_DEFUN([read_test], [AC_LANG_SOURCE(
+dnl 	esyscmd(tools/m4esc.sh config-tests/$1))])
+dnl 
+dnl AC_MSG_CHECKING([compiler standards compliance])
+dnl AC_COMPILE_IFELSE(
+dnl 	[read_test(cpp-17-test.cpp)], [],
+dnl 	[AC_MSG_ERROR([Your c++ compiler is not capable of compiling libcifpp, please upgrade])])
+dnl AC_MSG_RESULT(ok)
 
 AC_PROG_INSTALL
 AC_ENABLE_STATIC

include/cif++/Cif++.hpp

@@ -873,9 +873,9 @@ std::string KeyIsNotConditionImpl<std::string>::str() const
 	return mItemTag + " != " + mValue;
 }
 
-template<typename COMP>
 struct KeyCompareConditionImpl : public ConditionImpl
 {
+	template<typename COMP>
 	KeyCompareConditionImpl(const std::string& ItemTag, COMP&& comp)
 		: mItemTag(ItemTag), mComp(std::move(comp)) {}
 	
@@ -893,7 +893,7 @@ struct KeyCompareConditionImpl : public ConditionImpl
 	
 	std::string mItemTag;
 	size_t mItemIx;
-	COMP mComp;
+	std::function<bool(const Category&, const Row&)> mComp;
 };
 
 struct KeyMatchesConditionImpl : public ConditionImpl
@@ -1792,8 +1792,7 @@ void KeyIsNotConditionImpl<T>::prepare(const Category& c)
 	mItemIx = c.getColumnIndex(mItemTag);
 }
 
-template<typename T>
-void KeyCompareConditionImpl<T>::prepare(const Category& c)
+inline void KeyCompareConditionImpl::prepare(const Category& c)
 {
 	mItemIx = c.getColumnIndex(mItemTag);
 }