Grammar reference¶

Every PLUTO construct currently supported by the transpiler. The full formal grammar lives in src/pluto_ecss/grammar.lark.

Procedure structure¶

procedure
  declare ... end declare           // optional, event declarations
  preconditions ... end preconditions  // optional
  watchdog ... end watchdog         // optional, event handlers
  main
    ...                             // required
  end main
  confirmation ... end confirmation // optional
end procedure

Sections may appear in any order. main is required; the others are optional.

Event declarations¶

declare
  event boom described by Critical failure
  event chaos2
end declare

Multiple events can be comma-separated or newline-separated.

Activity calls¶

initiate Switch on Star Tracker1                           // fire-and-forget
initiate and confirm Switch on Reaction Wheel3              // wait for completion
initiate and confirm Switch off Reaction Wheel3 of AOC of Satellite

A qualified target like X of Y of Z is resolved against the runtime's system element registry.

Steps¶

initiate and confirm step BRING UP STAR TRACKER
  main
    initiate and confirm Switch on Star Tracker1;
    initiate and confirm Switch on Star Tracker2;
  end main
end step

Parallel execution¶

in parallel until all complete
  initiate and confirm step A
    main
      initiate and confirm Switch on Star Tracker1;
    end main
  end step;
  initiate and confirm step B
    main
      initiate and confirm Switch on Star Tracker2;
    end main
  end step;
end parallel

Variants:

in parallel until all complete … end parallel — waits for every branch.
in parallel until one completes … end parallel — returns as soon as any branch finishes.

Control flow¶

if mode = 1 then
  inform user "nominal"
else
  inform user "safe"
end if

case mode of
  when 1 do inform user "STANDBY"
  when 2 do inform user "NOMINAL"
  otherwise inform user "UNKNOWN"
end case

while c < 10 do
  c := c + 1
end while

for i := 1 to 5 do
  log "tick"
end for

repeat
  log "hi"
until done = 1
end repeat

Waits and timeouts¶

wait for event ready                           // blocks until raised
wait for event ready with timeout 5            // raises after 5s
wait until counter >= 3                        // poll until true
wait until temperature < 0.5 with timeout 30

with timeout E also applies to while and repeat.

Watchdog handlers¶

watchdog
  on boom do
    inform user "handling boom"
    initiate and confirm Switch off Reaction Wheel3
  end on
end watchdog

When raise event boom is reached in main, the corresponding handler runs synchronously before execution continues.

Output¶

log "message"             // routed to the Python logger (visible with pluto-ecss -v)
inform user "message"     // printed to stdout

Expressions¶

x := 1 + 2 * 3
done := (mode = 1) and (counter > threshold)
ok := not failed

Operators: +, -, *, /, =, <>, <, <=, >, >=, and, or, not. Operands are numbers, strings ("..."), or qualified names.

Assignment¶

counter := 0
counter := counter + 1

Comments¶

// this is a line comment