[ 
https://issues.apache.org/jira/browse/ARROW-1491?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16278494#comment-16278494
 ] 

ASF GitHub Bot commented on ARROW-1491:
---------------------------------------

xhochy commented on a change in pull request #1387: ARROW-1491: [C++] Add 
casting implementations from strings to numbers or boolean
URL: https://github.com/apache/arrow/pull/1387#discussion_r154934826
 
 

 ##########
 File path: cpp/src/arrow/compute/kernels/cast.cc
 ##########
 @@ -660,6 +663,100 @@ struct CastFunctor<T, DictionaryType,
   }
 };
 
+// ----------------------------------------------------------------------
+// String to Number
+
+template <typename O>
+struct CastFunctor<O, StringType,
+                   typename std::enable_if<std::is_base_of<Number, 
O>::value>::type> {
+  void operator()(FunctionContext* ctx, const CastOptions& options,
+                  const ArrayData& input, ArrayData* output) {
+    using out_type = typename O::c_type;
+    StringArray input_array(input.Copy());
+
+    if (input_array.null_count() > 0) {
+      std::stringstream ss;
+      ss << "Failed to cast NA into " << output->type->ToString();
+      ctx->SetStatus(Status(StatusCode::SerializationError, ss.str()));
+      return;
+    }
+
+    auto out_data = GetMutableValues<out_type>(output, 1);
+
+    std::function<out_type(const std::string&)> cast_func;
+    if (output->type->id() == Type::INT8 || output->type->id() == Type::UINT8) 
{
+      cast_func = [](const std::string& s) {
+        return boost::numeric_cast<out_type>(boost::lexical_cast<int>(s));
 
 Review comment:
   Can you add a comment why this special case is needed?

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> [C++] Add casting implementations from strings to numbers or boolean
> --------------------------------------------------------------------
>
>                 Key: ARROW-1491
>                 URL: https://issues.apache.org/jira/browse/ARROW-1491
>             Project: Apache Arrow
>          Issue Type: New Feature
>          Components: C++
>            Reporter: Wes McKinney
>            Assignee: Licht Takeuchi
>              Labels: pull-request-available
>             Fix For: 0.9.0
>
>




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