Implement DataFrame.eval using libcudf ASTs

cpp/include/cudf/ast/expressions.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020-2021, NVIDIA CORPORATION.
+ * Copyright (c) 2020-2022, NVIDIA CORPORATION.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -21,6 +21,8 @@
 #include <cudf/types.hpp>
 #include <cudf/utilities/error.hpp>
 
+#include <cstdint>
+
 namespace cudf {
 namespace ast {
 
@@ -53,7 +55,7 @@ struct expression {
 /**
  * @brief Enum of supported operators.
  */
-enum class ast_operator {
+enum class ast_operator : int32_t {
   // Binary operators
   ADD,         ///< operator +
   SUB,         ///< operator -

python/cudf/cudf/_lib/__init__.py

@@ -1,7 +1,8 @@
-# Copyright (c) 2020-2021, NVIDIA CORPORATION.
+# Copyright (c) 2020-2022, NVIDIA CORPORATION.
 import numpy as np
 
 from . import (
+    ast,
     avro,
     binaryop,
     concat,

python/cudf/cudf/_lib/ast.pxd

@@ -0,0 +1,33 @@
+# Copyright (c) 2022, NVIDIA CORPORATION.
+
+from libc.stdint cimport int32_t, int64_t
+from libcpp.memory cimport unique_ptr
+
+from cudf._lib.cpp.ast cimport column_reference, expression, literal, operation
+from cudf._lib.cpp.scalar.scalar cimport numeric_scalar
+
+ctypedef enum scalar_type_t:
+    INT
+    DOUBLE
+
+
+ctypedef union int_or_double_scalar_ptr:
+    unique_ptr[numeric_scalar[int64_t]] int_ptr
+    unique_ptr[numeric_scalar[double]] double_ptr
+
+
+cdef class Expression:
+    cdef unique_ptr[expression] c_obj
+
+
+cdef class Literal(Expression):
+    cdef scalar_type_t c_scalar_type
+    cdef int_or_double_scalar_ptr c_scalar
+
+
+cdef class ColumnReference(Expression):
+    pass
+
+
+cdef class Operation(Expression):
+    pass