Expresso: A simple expressions language with polymorphic extensible row types

Re:Expresso: A simple expressions language with polymorphic ... by acjohnson55 on Saturday November 17, 2018 @11:42PM (#18478911)

It seems like there's just a global namespace of labels. This reminds me of the situation in Javascript before symbols were introduced. I'm curious why this choice was made?

[ Parent | on HN ]

Re:Expresso: A simple expressions language with polymorphic ... by willtim on Sunday November 18, 2018 @04:12AM (#18479496)

Labels in Expresso are just type-level symbols. Label names can be re-used over and over again in different records and variants. This works fine because a name is not tired to any particular nominal type (like a constructor in Haskell or Java).

[ Parent | on HN ]

Re:Expresso: A simple expressions language with polymorphic ... by acjohnson55 on Tuesday November 20, 2018 @09:36PM (#18499784)

But it seems like it would be an error to concatenate two records with a name clash, though, right?

[ Parent | on HN ]

Re:Expresso: A simple expressions language with polymorphic ... by willtim on Friday November 30, 2018 @02:40AM (#18567436)

Yes because duplicate labels are not allowed within the scope of a single record (you can specify which one overrides the other, but perhaps we also need a convenient rename syntax). This point was that different records can happily contain the same field names. The situation is the same as SQL.

[ Parent | on HN ]