Dhall - map on record field

Question

I have a type

let Resource = \(a : Type) ->
  { name : Text
  , type : Text
  , properties : a
  }

and a function foo : InstanceTemplateProperties -> Properties.

I need to create a function Resource InstanceTemplateProperties -> Resource Properties.

I could write it as

\(p : Resource InstanceTemplateProperties) ->
  { name = p.name
  , type = p.type
  , properties = foo p.properties
  } : Resource Properties

but it looks really cumbersome. Is there an easier and more idiomatic way to do this?

Just using a short, generic name like `p` instead of `instanceTemplateProperties` would be a good start. — chepner, Jan 13 '20 at 17:38

score 1 · Accepted Answer · edited Jan 14 '20 at 15:38

1

You can use // to merge the updated properties into the original.

(\p : Resource InstanceTemplateProperties) ->
  p // {properties = foo p.properties)

edited Jan 14 '20 at 15:38

answered Jan 13 '20 at 17:49

chepner

Thanks for the edit; I obviously misremembered the operator, and I think I misread the Unicode operator for a single ASCII `/` without seeing the ASCII equivalent. – chepner Jan 14 '20 at 15:43

1 Answers1