Fix docstrings and change index names

Author: AlenkaF

cpp/src/arrow/record_batch.h

@@ -90,7 +90,7 @@ class ARROW_EXPORT RecordBatch {
   /// in the resulting struct array.
   Result<std::shared_ptr<StructArray>> ToStructArray() const;
 
-  /// \brief Convert record batch with one data type to Tensor
+  /// \brief Convert RecordBatch to Tensor
   ///
   /// Create a Tensor object with shape (number of rows, number of columns) and
   /// strides (type size in bytes, type size in bytes * number of rows).

cpp/src/arrow/table.h

@@ -101,7 +101,7 @@ class ARROW_EXPORT Table {
   static Result<std::shared_ptr<Table>> FromChunkedStructArray(
       const std::shared_ptr<ChunkedArray>& array);
 
-  /// \brief Convert table with one data type to Tensor
+  /// \brief Convert Table to Tensor
   ///
   /// Create a Tensor object with shape (number of rows, number of columns) and
   /// strides (type size in bytes, type size in bytes * number of rows).

cpp/src/arrow/tensor.cc

@@ -270,15 +270,14 @@ struct ConvertArrayToTensorRowMajorVisitor {
       auto in_values = ArraySpan(in_data).GetSpan<In>(1, in_data.length);
 
       if (in_data.null_count == 0) {
-        for (int64_t data_idx = 0; data_idx < in_data.length; ++data_idx) {
-          out_values[(data_idx + chunk_idx) * num_cols + col_idx] =
-              static_cast<Out>(in_values[data_idx]);
+        for (int64_t i = 0; i < in_data.length; ++i) {
+          out_values[(i + chunk_idx) * num_cols + col_idx] =
+              static_cast<Out>(in_values[i]);
         }
       } else {
-        for (int64_t data_idx = 0; data_idx < in_data.length; ++data_idx) {
-          out_values[(data_idx + chunk_idx) * num_cols + col_idx] =
-              in_data.IsNull(data_idx) ? static_cast<Out>(NAN)
-                                       : static_cast<Out>(in_values[data_idx]);
+        for (int64_t i = 0; i < in_data.length; ++i) {
+          out_values[(i + chunk_idx) * num_cols + col_idx] =
+              in_data.IsNull(i) ? static_cast<Out>(NAN) : static_cast<Out>(in_values[i]);
         }
       }
       return Status::OK();
@@ -292,21 +291,21 @@ inline void ConvertColumnsToTensor(const Table& table, uint8_t* out, bool row_ma
   using CType = typename arrow::TypeTraits<DataType>::CType;
   auto* out_values = reinterpret_cast<CType*>(out);
 
-  int i = 0;
+  int col_idx = 0;
   for (const auto& column : table.columns()) {
-    int j = 0;
+    int chunk_idx = 0;
     for (const auto& chunk : column->chunks()) {
       if (row_major) {
-        ConvertArrayToTensorRowMajorVisitor<CType> visitor{out_values, *chunk->data(),
-                                                           table.num_columns(), i, j};
+        ConvertArrayToTensorRowMajorVisitor<CType> visitor{
+            out_values, *chunk->data(), table.num_columns(), col_idx, chunk_idx};
         DCHECK_OK(VisitTypeInline(*chunk->type(), &visitor));
-        j = j + static_cast<int>(chunk->length());
+        chunk_idx = chunk_idx + static_cast<int>(chunk->length());
       } else {
         ConvertArrayToTensorVisitor<CType> visitor{out_values, *chunk->data()};
         DCHECK_OK(VisitTypeInline(*chunk->type(), &visitor));
       }
     }
-    i++;
+    col_idx++;
   }
 }