Remove some superfluous actions generated by TAB

Author: rbrott

road-runner/actions/src/main/kotlin/com/acmerobotics/roadrunner/Actions.kt

@@ -142,10 +142,10 @@ class NullAction : Action {
 }
 
 private fun seqCons(hd: Action, tl: Action): Action =
-    if (tl is SequentialAction) {
-        SequentialAction(listOf(hd) + tl.initialActions)
-    } else {
-        SequentialAction(hd, tl)
+    when (tl) {
+        is NullAction -> hd
+        is SequentialAction -> SequentialAction(listOf(hd) + tl.initialActions)
+        else -> SequentialAction(hd, tl)
     }
 
 private sealed class MarkerFactory(
@@ -303,10 +303,10 @@ class TrajectoryActionBuilder private constructor(
                         }
                     }
 
-                    if (actions.size == 1) {
-                        Pair(actions.first(), msRem)
-                    } else {
-                        Pair(ParallelAction(actions), msRem)
+                    when (actions.size) {
+                        0 -> Pair(NullAction(), msRem)
+                        1 -> Pair(actions.first(), msRem)
+                        else -> Pair(ParallelAction(actions), msRem)
                     }
                 }
 
@@ -363,7 +363,12 @@ class TrajectoryActionBuilder private constructor(
 
         return if (n == 0) {
             TrajectoryActionBuilder(this, tb, 0, lastPoseUnmapped, lastPose, lastTangent, emptyList()) { tail ->
-                cont(ParallelAction(tail, seqCons(SleepAction(dt), a)))
+                val m = seqCons(SleepAction(dt), a)
+                if (tail is NullAction) {
+                    cont(m)
+                } else {
+                    cont(ParallelAction(tail, m))
+                }
             }
         } else {
             TrajectoryActionBuilder(
@@ -864,6 +869,6 @@ class TrajectoryActionBuilder private constructor(
     }
 
     fun build(): Action {
-        return endTrajectory().cont(SequentialAction())
+        return endTrajectory().cont(NullAction())
     }
 }

road-runner/actions/src/test/kotlin/com/acmerobotics/roadrunner/ActionRegressionTest.kt

@@ -55,6 +55,7 @@ fun sexpFromAction(a: Action): Sexp =
         is SleepAction -> Sexp.list(Sexp.Atom("sleep"), Sexp.Atom(String.format("%.10f", a.dt)))
         is SequentialAction -> Sexp.list(listOf(Sexp.Atom("seq")) + a.initialActions.map(::sexpFromAction))
         is ParallelAction -> Sexp.list(listOf(Sexp.Atom("par")) + a.initialActions.map(::sexpFromAction))
+        is NullAction -> Sexp.Atom("null")
         else -> Sexp.Atom("unk")
     }
 

road-runner/actions/values.txt

@@ -1,21 +1,21 @@
 basic
-(seq traj)
-(seq traj)
+traj
+traj
 
 continuity
 (seq traj (sleep 10.0000000000) traj)
 (seq traj traj traj)
 
 time markers
-(seq traj traj (par (seq traj) (seq (sleep 2.0000000000) A)))
+(seq traj traj (par traj (seq (sleep 2.0000000000) A)))
 ( seq
   traj
   traj
-  (par (seq traj) (seq (sleep 2.0000000000) A) (seq (sleep 2.5000000000) B))
+  (par traj (seq (sleep 2.0000000000) A) (seq (sleep 2.5000000000) B))
 )
-(par (seq) (seq (sleep 1.0000000000) a))
+(seq (sleep 1.0000000000) a)
 
 disp markers
-(par (seq traj) (seq (sleep 0.4472135955) A))
-(par (seq traj) (seq (sleep 0.3162277660) A))
+(par traj (seq (sleep 0.4472135955) A))
+(par traj (seq (sleep 0.3162277660) A))
 (par (seq traj traj) (seq (sleep 0.3162277660) A))