Add istitle to string UDFs (#11738)

This PR adds support for the use of the`str.istitle()` method within udfs for `apply`.

Authors:
  - https://github.com/brandon-b-miller
  - Vyas Ramasubramani (https://github.com/vyasr)

Approvers:
  - David Wendt (https://github.com/davidwendt)
  - Vyas Ramasubramani (https://github.com/vyasr)

URL: #11738

python/cudf/cudf/core/udf/strings_lowering.py

@@ -19,6 +19,7 @@
     isdigit_impl,
     islower_impl,
     isspace_impl,
+    istitle_impl,
     isupper_impl,
     len_impl,
     rfind_impl,
@@ -123,3 +124,4 @@ def masked_unary_func_impl(context, builder, sig, args):
 create_masked_unary_identifier_func("MaskedType.islower", islower_impl)
 create_masked_unary_identifier_func("MaskedType.isspace", isspace_impl)
 create_masked_unary_identifier_func("MaskedType.isdecimal", isdecimal_impl)
+create_masked_unary_identifier_func("MaskedType.istitle", istitle_impl)

python/cudf/cudf/tests/test_udf_masked_ops.py

@@ -56,6 +56,11 @@ def str_udf_data():
                 "cudf",
                 "cuda",
                 "gpu",
+                "This Is A Title",
+                "This is Not a Title",
+                "Neither is This a Title",
+                "NoT a TiTlE",
+                "123 Title Works",
             ]
         }
     )
@@ -839,6 +844,14 @@ def func(row):
     run_masked_udf_test(func, str_udf_data, check_dtype=False)
 
 
+@string_udf_test
+def test_string_udf_istitle(str_udf_data):
+    def func(row):
+        return row["str_col"].istitle()
+
+    run_masked_udf_test(func, str_udf_data, check_dtype=False)
+
+
 @string_udf_test
 def test_string_udf_count(str_udf_data, substr):
     def func(row):

python/strings_udf/cpp/include/cudf/strings/udf/char_types.cuh

@@ -183,6 +183,30 @@ __device__ inline bool is_lower(cudf::strings::detail::character_flags_table_typ
     flags_table, d_str, string_character_types::LOWER, string_character_types::CASE_TYPES);
 }
 
+/**
+ * @brief Returns true if string is in title case
+ *
+ * @param tables The char tables required for checking characters
+ * @param d_str Input string to check
+ * @return True if string is in title case
+ */
+__device__ inline bool is_title(cudf::strings::detail::character_flags_table_type* flags_table,
+                                string_view d_str)
+{
+  auto valid                 = false;  // requires one or more cased characters
+  auto should_be_capitalized = true;   // current character should be upper-case
+  for (auto const chr : d_str) {
+    auto const code_point = cudf::strings::detail::utf8_to_codepoint(chr);
+    auto const flag       = code_point <= 0x00FFFF ? flags_table[code_point] : 0;
+    if (cudf::strings::detail::IS_UPPER_OR_LOWER(flag)) {
+      if (should_be_capitalized == !cudf::strings::detail::IS_UPPER(flag)) return false;
+      valid = true;
+    }
+    should_be_capitalized = !cudf::strings::detail::IS_UPPER_OR_LOWER(flag);
+  }
+  return valid;
+}
+
 }  // namespace udf
 }  // namespace strings
 }  // namespace cudf

python/strings_udf/cpp/src/strings/udf/shim.cu

@@ -198,6 +198,15 @@ extern "C" __device__ int pyisalpha(bool* nb_retval, void const* str, std::int64
   return 0;
 }
 
+extern "C" __device__ int pyistitle(bool* nb_retval, void const* str, std::int64_t chars_table)
+{
+  auto str_view = reinterpret_cast<cudf::string_view const*>(str);
+
+  *nb_retval = is_title(
+    reinterpret_cast<cudf::strings::detail::character_flags_table_type*>(chars_table), *str_view);
+  return 0;
+}
+
 extern "C" __device__ int pycount(int* nb_retval, void const* str, void const* substr)
 {
   auto str_view    = reinterpret_cast<cudf::string_view const*>(str);

python/strings_udf/strings_udf/_typing.py

@@ -209,6 +209,7 @@ def resolve_count(self, mod):
     "islower",
     "isspace",
     "isnumeric",
+    "istitle",
 ]
 
 for func in bool_binary_funcs:

python/strings_udf/strings_udf/lowering.py

@@ -76,6 +76,7 @@ def _declare_binary_func(lhs, rhs, out, name):
 _string_view_isspace = _declare_bool_str_int_func("pyisspace")
 _string_view_isupper = _declare_bool_str_int_func("pyisupper")
 _string_view_islower = _declare_bool_str_int_func("pyislower")
+_string_view_istitle = _declare_bool_str_int_func("pyistitle")
 
 
 _string_view_count = cuda.declare_device(
@@ -285,3 +286,8 @@ def isupper_impl(st, tbl):
 @create_unary_identifier_func("StringView.islower")
 def islower_impl(st, tbl):
     return _string_view_islower(st, tbl)
+
+
+@create_unary_identifier_func("StringView.istitle")
+def istitle_impl(st, tbl):
+    return _string_view_istitle(st, tbl)

python/strings_udf/strings_udf/tests/test_string_udfs.py

@@ -89,6 +89,11 @@ def data():
         "cudf",
         "cuda",
         "gpu",
+        "This Is A Title",
+        "This is Not a Title",
+        "Neither is This a Title",
+        "NoT a TiTlE",
+        "123 Title Works",
     ]
 
 
@@ -228,6 +233,13 @@ def func(st):
     run_udf_test(data, func, "bool")
 
 
+def test_string_udf_istitle(data):
+    def func(st):
+        return st.istitle()
+
+    run_udf_test(data, func, "bool")
+
+
 def test_string_udf_len(data):
     def func(st):
         return len(st)