[C++] Add a VisitIntegerType helper

[pitrou]

Describe the enhancement requested

In visit_type_inline.h we have a VisitType that dispatches all existing data types to a generic callable (presumably a lambda or template function).

It would be useful to have a similar VisitIntegerType helper that assumes its input is an integer type. This would help implementing helpers for dictionary indices, take indices, etc.

For example this snippet could be reimplemented more tersely using said helper:

arrow/cpp/src/arrow/util/dict_util.cc

Lines 61 to 79 in 154962c

	const auto& dict_array_type = internal::checked_cast<const DictionaryType&>(*span.type);
	switch (dict_array_type.index_type()->id()) {
	case Type::UINT8:
	return LogicalNullCount<UInt8Type>(span);
	case Type::INT8:
	return LogicalNullCount<Int8Type>(span);
	case Type::UINT16:
	return LogicalNullCount<UInt16Type>(span);
	case Type::INT16:
	return LogicalNullCount<Int16Type>(span);
	case Type::UINT32:
	return LogicalNullCount<UInt32Type>(span);
	case Type::INT32:
	return LogicalNullCount<Int32Type>(span);
	case Type::UINT64:
	return LogicalNullCount<UInt64Type>(span);
	default:
	return LogicalNullCount<Int64Type>(span);
	}

Component(s)

C++

[pitrou]

@tadeja

[pitrou]

And we can similarly want a VisitRunEndType that dispatches over all 3 supported run-end types: INT16, INT32, INT64.

[pitrou]

Also @goel-skd

[goel-skd]

I can take it along with my current work. Will look at it in a couple of days

[goel-skd]

take