gidl/tests/example.idl

(def-newtype time_micros_t sint64_t)

-- comments should be haskell style, because we're suing parsec's haskell lexer

-- enums default to 32 bit width if you don't really care
(def-enum mode_t
 ((stabilize 0)
  (auto 1)))

-- or you can specify a width
(def-enum armed_t 
 8
 ((disarmed 0)
  (armed 1)))

(def-struct heartbeat_t
 ((time time_micros_t)
  (armed armed_t)))

(def-newtype lat_t sint32_t)
(def-newtype lon_t sint32_t)

-- Todo: allow attaching unit annotations to newtypes. The code generator will
-- provide the units as a human readable comment, and/or in some type/unit
-- system supported by the host language.
-- Todo: allow attaching predicates to newtypes. e.g., lon_t might have some
-- type (degrees * 10e-6), some predicate
-- (lambda (v) (and (gt v -180000000) (lte v 180000000)))

(def-newtype meters_t float_t)

(def-struct coordinate_t
 ((lat lat_t)
  (lon lon_t)
  (alt meters_t)))

(def-newtype waypoint_t coordinate_t)

-- Todo: the following interface syntax and semantics are a strawman.
-- Interfaces have methods that are either streams or attrs.
-- attrs take a parameter for access control.
-- streams take a parameter for their default period in hz (none should default
-- to zero). they also implicitly define an attr $(steamname)-stream-rate,
-- which permits changing the stream rate at runtime.

(def-interface vehicle_i
 ((heartbeat (stream 10 heartbeat_t))))

-- Interfaces implement java-style inheritance. No shadowing of inherited method
-- names permitted.

(def-interface controllable_vehicle_i
  ((current_waypoint (attr read      waypoint_t))
   (next_waypoint    (attr readwrite waypoint_t)))
  (vehicle_i)) -- Inherits from interface vehicle

-- The idea here is that, when negotiating a gidl connection, the client can
-- specify or negotiate what interface is supported.
-- this may be communicated by just sending the string name, or potentially by
-- sending the entire serialized schema. At very least, the client and server
-- should check agreement of their type schemas, probably by having the client
-- send a sha1-hash of the serialized type schema.
-- This allows us to specify various kinds of vehicles might exist without
-- repeating ourselves, and provides a way to
-- manage new functionality without breaking legacy code.