#10. Headers

Headers are shaped a bit like structs, but they play by different rules.

#Start the demo server

telepact demo-server --port 8000

#Look at internal header definitions

curl -s localhost:8000/api -d '[{}, {"fn.api_": {"includeInternal!": true}}]'

For example:

{
  "headers.Id_": {
    "@id_": "any"
  },
  "->": {
    "@id_": "any"
  }
}

Headers differ from structs in two important ways:

1. every defined header field is already optional

2. undefined header fields are still allowed

That is why header names use @ and do not use !.

#A real example with @id_

curl -s localhost:8000/api -d '[{"@id_": "lesson-10"}, {"fn.add": {"x": 1, "y": 2}}]'

Response:

[{"@id_": "lesson-10"}, {"Ok_": {"result": 3}}]

So @id_ is just a correlation helper: the server reflects it back.

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