Added split_on_first() and split_on_last().

dlib/string/string.h

@@ -856,6 +856,74 @@ namespace dlib
             return _dT(charT,"");
     }
 
+// ----------------------------------------------------------------------------------------
+
+    template <
+        typename charT,
+        typename traits,
+        typename alloc
+        >
+    std::pair<std::basic_string<charT,traits,alloc>, std::basic_string<charT,traits,alloc> > 
+    split_on_first (
+        const std::basic_string<charT,traits,alloc>& str,
+        const charT* delim = _dT(charT," \n\r\t")
+    )
+    {
+        typename std::basic_string<charT,traits,alloc>::size_type delim_pos = str.find_first_of(delim);
+        if (delim_pos != std::basic_string<charT,traits,alloc>::npos)
+            return std::make_pair(str.substr(0, delim_pos), str.substr(delim_pos+1));
+        else
+            return std::make_pair(str, _dT(charT,""));
+    }
+
+    template <
+        typename charT,
+        typename traits,
+        typename alloc
+        >
+    inline std::pair<std::basic_string<charT,traits,alloc>, std::basic_string<charT,traits,alloc> > 
+    split_on_first (
+        const std::basic_string<charT,traits,alloc>& str,
+        const std::basic_string<charT,traits,alloc>& delim 
+    )
+    {
+        return split_on_first(str, delim.c_str());
+    }
+
+// ----------------------------------------------------------------------------------------
+
+    template <
+        typename charT,
+        typename traits,
+        typename alloc
+        >
+    std::pair<std::basic_string<charT,traits,alloc>, std::basic_string<charT,traits,alloc> > 
+    split_on_last (
+        const std::basic_string<charT,traits,alloc>& str,
+        const charT* delim = _dT(charT," \n\r\t")
+    )
+    {
+        typename std::basic_string<charT,traits,alloc>::size_type delim_pos = str.find_last_of(delim);
+        if (delim_pos != std::basic_string<charT,traits,alloc>::npos)
+            return std::make_pair(str.substr(0, delim_pos), str.substr(delim_pos+1));
+        else
+            return std::make_pair(str, _dT(charT,""));
+    }
+
+    template <
+        typename charT,
+        typename traits,
+        typename alloc
+        >
+    inline std::pair<std::basic_string<charT,traits,alloc>, std::basic_string<charT,traits,alloc> > 
+    split_on_last (
+        const std::basic_string<charT,traits,alloc>& str,
+        const std::basic_string<charT,traits,alloc>& delim 
+    )
+    {
+        return split_on_last(str, delim.c_str());
+    }
+
 // ----------------------------------------------------------------------------------------
 
     template <

dlib/string/string_abstract.h

@@ -523,6 +523,86 @@ namespace dlib
             - returns right_substr(str, std::basic_string<charT,traits,alloc>(delim))
     !*/
 
+// ----------------------------------------------------------------------------------------
+
+    template <
+        typename charT,
+        typename traits,
+        typename alloc
+        >
+    std::pair<std::basic_string<charT,traits,alloc>, std::basic_string<charT,traits,alloc> > 
+    split_on_first (
+        const std::basic_string<charT,traits,alloc>& str,
+        const charT* delim = _dT(charT, " \n\r\t")
+    );
+    /*!
+        ensures
+            - This function splits string into two parts, the split is based on the first
+              occurrence of any character from delim.  
+            - let delim_pos = str.find_first_of(delim)
+            - if (delim_pos == std::string::npos) then
+                - returns make_pair(str,"")
+            - else
+                - return make_pair(str.substr(0, delim_pos), str.substr(delim_pos+1));
+    !*/
+
+    template <
+        typename charT,
+        typename traits,
+        typename alloc
+        >
+    std::pair<std::basic_string<charT,traits,alloc>, std::basic_string<charT,traits,alloc> > 
+    split_on_first (
+        const std::basic_string<charT,traits,alloc>& str,
+        const std::basic_string<charT,traits,alloc>& delim 
+    );
+    /*!
+        requires
+            - delim == a valid null-terminated C string
+        ensures
+            - returns split_on_first(str, delim.c_str())
+    !*/
+
+// ----------------------------------------------------------------------------------------
+
+    template <
+        typename charT,
+        typename traits,
+        typename alloc
+        >
+    std::pair<std::basic_string<charT,traits,alloc>, std::basic_string<charT,traits,alloc> > 
+    split_on_last (
+        const std::basic_string<charT,traits,alloc>& str,
+        const charT* delim = _dT(charT, " \n\r\t")
+    );
+    /*!
+        ensures
+            - This function splits string into two parts, the split is based on the last 
+              occurrence of any character from delim.  
+            - let delim_pos = str.find_last_of(delim)
+            - if (delim_pos == std::string::npos) then
+                - returns make_pair(str,"")
+            - else
+                - return make_pair(str.substr(0, delim_pos), str.substr(delim_pos+1));
+    !*/
+
+    template <
+        typename charT,
+        typename traits,
+        typename alloc
+        >
+    std::pair<std::basic_string<charT,traits,alloc>, std::basic_string<charT,traits,alloc> > 
+    split_on_last (
+        const std::basic_string<charT,traits,alloc>& str,
+        const std::basic_string<charT,traits,alloc>& delim 
+    );
+    /*!
+        requires
+            - delim == a valid null-terminated C string
+        ensures
+            - returns split_on_last(str, delim.c_str())
+    !*/
+
 // ----------------------------------------------------------------------------------------
 
     template <

dlib/test/string.cpp

@@ -242,6 +242,59 @@ namespace
         DLIB_TEST(wv.size() == 2);
         DLIB_TEST(wv[0] == L"test");
         DLIB_TEST(wv[1] == L"string");
+
+
+        wstr = L"test string hah";
+        DLIB_TEST(split_on_first(wstr).first == L"test");
+        DLIB_TEST(split_on_first(wstr).second == L"string hah");
+        DLIB_TEST(split_on_first(wstr,L"#").first == L"test string hah");
+        DLIB_TEST(split_on_first(wstr,L"#").second == L"");
+        DLIB_TEST(split_on_last(wstr).first == L"test string");
+        DLIB_TEST(split_on_last(wstr).second == L"hah");
+        DLIB_TEST(split_on_last(wstr,L"#").first == L"test string hah");
+        DLIB_TEST(split_on_last(wstr,L"#").second == L"");
+        wstr = L"";
+        DLIB_TEST(split_on_first(wstr).first == L"");
+        DLIB_TEST(split_on_first(wstr).second == L"");
+
+        str = "test string hah";
+        DLIB_TEST(split_on_first(str).first == "test");
+        DLIB_TEST(split_on_first(str).second == "string hah");
+        DLIB_TEST(split_on_first(str,"#").first == "test string hah");
+        DLIB_TEST(split_on_first(str,"#").second == "");
+        DLIB_TEST(split_on_last(str).first == "test string");
+        DLIB_TEST(split_on_last(str).second == "hah");
+        DLIB_TEST(split_on_last(str,"#").first == "test string hah");
+        DLIB_TEST(split_on_last(str,"#").second == "");
+        str = "";
+        DLIB_TEST(split_on_first(str).first == "");
+        DLIB_TEST(split_on_first(str).second == "");
+
+        wstr = L"test.string.hah";
+        DLIB_TEST(split_on_first(wstr,L".").first == L"test");
+        DLIB_TEST(split_on_first(wstr,L".").second == L"string.hah");
+        DLIB_TEST(split_on_first(wstr).first == L"test.string.hah");
+        DLIB_TEST(split_on_first(wstr).second == L"");
+        DLIB_TEST(split_on_last(wstr,L".").first == L"test.string");
+        DLIB_TEST(split_on_last(wstr,L".").second == L"hah");
+        DLIB_TEST(split_on_last(wstr).first == L"test.string.hah");
+        DLIB_TEST(split_on_last(wstr).second == L"");
+        wstr = L"";
+        DLIB_TEST(split_on_first(wstr).first == L"");
+        DLIB_TEST(split_on_first(wstr).second == L"");
+
+        str = "test.string.hah";
+        DLIB_TEST(split_on_first(str,".").first == "test");
+        DLIB_TEST(split_on_first(str,".").second == "string.hah");
+        DLIB_TEST(split_on_first(str).first == "test.string.hah");
+        DLIB_TEST(split_on_first(str).second == "");
+        DLIB_TEST(split_on_last(str,".").first == "test.string");
+        DLIB_TEST(split_on_last(str,".").second == "hah");
+        DLIB_TEST(split_on_last(str).first == "test.string.hah");
+        DLIB_TEST(split_on_last(str).second == "");
+        str = "";
+        DLIB_TEST(split_on_first(str).first == "");
+        DLIB_TEST(split_on_first(str).second == "");
     }