MAX_NUMBER_OF_MEMBERS

[mjhurd]

Hi,

Boost Hana's wonderfulness is unavailable for some autogen structs from table work I'm working with.

I have more than 62 columns - to be members - of the table - to be struct.

Unfortunately, the ERB in hana/detail doesn't like the idea of more than 62 members in a struct.

MAX_NUMBER_OF_MEMBERS = (ENV["MAX_NUMBER_OF_MEMBERS"] || 40).to_i raise "MAX_NUMBER_OF_MEMBERS must be <= 62" if MAX_NUMBER_OF_MEMBERS > 62

Pretty sensible for handcrafting but a bit limiting for my autogen work. Any thoughts on how best to raise the bar to 79 or 99 members?

Kind regards,

--Matt.

[ricejasonf]

It looks like the ERB is just generating preprocessor macros which have a limit to the amount of arguments that a macro can receive.

The docs for Struct show that you can implement hana::accessors for your type directly instead of using the macro. It's not very pretty, but if you are generating code heterogeneously (outside of c++) that probably doesn't matter.

See the examples below "Minimal Complete Definition" here: Struct

[mjhurd]

Thanks for the link to Struct. That'll do the job I need.

[ldionne]

I was away over the holidays. Reopening since I think we need a better solution. The ERB could generate the macros it needs for up to the right number of elements. In other words, we could lift the restriction that MAX_NUMBER_OF_MEMBERS <= 62.

[ldionne]

This should now be addressed. You can now generate struct_macros.hpp without any restriction on the number of members. This will be in Boost 1.67.