Add Napkin #12 to dance list.

www/js/danceLibrary.ts

@@ -48,6 +48,7 @@ export const dances: ContraDBDance[] = [
   { "title": "Magnetic Waves", "choreographer_name": "Isaac Banner", "start_type": "Becket", "preamble": "", "figures": [{ "parameter_values": ["gentlespoons", "", false, "ladles%%2", "across", false, false, false, false, 14], "move": "hey" }, { "parameter_values": ["ladles", false, 90, 2], "move": "allemande", "note": "to short waves" }, { "parameter_values": [false, "across", true, "ladles", false, "partners", 4], "move": "form an ocean wave" }, { "parameter_values": ["partners", true, 180, 2], "move": "allemande" }, { "parameter_values": ["gentlespoons", false, false, 2], "move": "pull by dancers" }, { "parameter_values": ["neighbors", "none", 8], "move": "swing" }, { "parameter_values": [true, "across", true, "ladles", false, "neighbors", 8], "move": "form an ocean wave" }, { "parameter_values": ["along", true, 2], "move": "pass through", "progression": 1 }, { "parameter_values": ["ladles", 360, 6], "move": "mad robin" }, { "parameter_values": ["single-file circle left 1 place", 2], "move": "custom" }, { "parameter_values": ["partners", "meltdown", 14], "move": "swing" }], "notes": "", "hook": "Pass the ocean to mad robin progression", "id": 1987 },
   { "title": "March for Andrea", "choreographer_name": "Isaac Banner", "start_type": "Becket", "preamble": "Andrea Nettleton told me she wished callers would do more down the halls, but all the options in my box were pretty basic and I wanted something that used it as less of an \"away we go\" and more of a buildup. ", "figures": [{ "parameter_values": ["ladles", true, "partners", 8], "move": "revolving door" }, { "parameter_values": ["neighbors", "none", 8], "move": "swing", "note": "and end facing down" }, { "parameter_values": ["everyone", "all", "forward", "turn-alone", 8], "move": "down the hall" }, { "parameter_values": ["everyone", "all", "forward", "circle", 8], "move": "up the hall" }, { "parameter_values": [4], "move": "balance the ring" }, { "parameter_values": ["partners", 4], "move": "California twirl", "progression": 1 }, { "parameter_values": [4], "move": "balance the ring" }, { "parameter_values": ["gentlespoons", "neighbors", true, 4], "move": "roll away" }, { "parameter_values": [4], "move": "balance the ring" }, { "parameter_values": ["gentlespoons", "partners", false, 4], "move": "give & take" }, { "parameter_values": ["partners", "none", 8], "move": "swing" }], "notes": "", "hook": "Down the hall without the default circle left", "id": 685 },
   { "title": "Napkin #11", "choreographer_name": "Isaac Banner", "start_type": "improper", "preamble": "", "figures": [{ "parameter_values": ["neighbors", false, false, 4], "move": "box the gnat" }, { "parameter_values": ["ladles", false, true, 4], "move": "pull by dancers" }, { "parameter_values": ["partners", "none", 8], "move": "swing" }, { "parameter_values": ["gentlespoons", false, 540, 8], "move": "allemande" }, { "parameter_values": ["neighbors", "none", 8], "move": "swing" }, { "parameter_values": ["ladles", true, "across", 8], "move": "chain" }, { "parameter_values": [false, 4], "move": "long lines" }, { "parameter_values": ["ladles", "partners", false, 4], "move": "roll away", "note": "on the way back" }, { "parameter_values": [true, 270, 8], "move": "circle" }, { "parameter_values": ["neighbors", false, true, 4], "move": "box the gnat" }, { "parameter_values": ["neighbors", false, true, 4], "move": "pull by dancers", "progression": 1 }], "notes": "", "hook": "No-balance box the gnat to swat the flea w/ next", "id": 2050 },
+  { "title": "Napkin #12", "choreographer_name": "Isaac Banner", "start_type": "improper", "preamble": "", "figures": [{ "parameter_values": ["neighbors", true, true, 8], "move": "box the gnat" }, { "parameter_values": ["gentlespoons", false, 540, 8], "move": "allemande" }, { "parameter_values": ["partners", "ladles", true, "half", "across", false, true, false, false, 8], "move": "hey" }, { "parameter_values": ["ladles", false, "across", 8], "move": "chain", "note": "to partners" }, { "parameter_values": ["robins ricochet, larks slide left", 4], "move": "custom", "note": "" }, { "parameter_values": ["partners", "none", 12], "move": "swing" }, { "parameter_values": ["gentlespoons", "", false, "half", "across", false, true, false, false, 8], "move": "hey", "note": "and catch left hands" }, { "parameter_values": [false, 360, "", 8], "move": "star", "note": ", larks fall in behind neighbors", "progression": 1 }], "notes": "", "hook": "", "id": 2112 },
   { "title": "Napkin #8", "choreographer_name": "Isaac Banner", "start_type": "improper", "preamble": "", "figures": [{ "parameter_values": [true, 8], "move": "petronella", "note": "right, end facing shadows" }, { "parameter_values": [true, 8], "move": "petronella", "note": "left" }, { "parameter_values": ["neighbors", "balance", 16], "move": "swing" }, { "parameter_values": ["gentlespoons", false, false, 4], "move": "pull by dancers", "note": "along right diagonal", "progression": 1 }, { "parameter_values": ["partners", "meltdown", 12], "move": "swing" }, { "parameter_values": [true, 270, 8], "move": "circle" }, { "parameter_values": ["neighbors", true, 360, 8], "move": "do si do" }], "notes": "", "hook": "Petronella right to shadow petronella left", "id": 1981 },
   { "title": "New Year, Same Old Charlie", "choreographer_name": "Isaac Banner", "start_type": "improper", "preamble": "", "figures": [{ "parameter_values": ["neighbors", "balance", 16], "move": "swing", "note": ", end facing down the hall" }, { "parameter_values": ["everyone", "all", "forward", "turn-alone", 8], "move": "down the hall" }, { "parameter_values": ["everyone", "all", "forward", "", 8], "move": "up the hall", "note": "and ones cast down one couple to new rings", "progression": 1 }, { "parameter_values": [true, 8], "move": "petronella" }, { "parameter_values": ["partners", "none", 8], "move": "swing" }, { "parameter_values": [true, 8], "move": "petronella" }, { "parameter_values": [4], "move": "balance the ring" }, { "parameter_values": ["partners", 4], "move": "California twirl", "progression": 1 }], "notes": "A2 cast down is mirrored with the active couple turning over their outside shoulders to drop down into a new ring of foot while the inactive couples finish moving up the hall.", "hook": "Cast down to rings balance, petronella to swing", "id": 1935 },
   { "title": "Not My Second Rodeo", "choreographer_name": "Isaac Banner", "start_type": "improper", "preamble": "", "figures": [{ "parameter_values": ["neighbors", "balance", 16], "move": "swing" }, { "parameter_values": ["gentlespoons", "", false, "half", "across", false, false, false, false, 8], "move": "hey" }, { "parameter_values": ["gentlespoons", false, 540, 8], "move": "allemande" }, { "parameter_values": ["partners", "meltdown", 16], "move": "swing" }, { "parameter_values": [true, 270, 8], "move": "circle" }, { "parameter_values": ["along", true, 0], "move": "pass through", "progression": 1 }, { "parameter_values": ["next neighbors", true, 360, 8], "move": "do si do" }], "notes": "Kind of but not really The Second Time Around by Jim Kitch. Hey-to-allemande offers a refreshing broken-hey-ish redux of allemande-to-hey and creates an illusion of less inactivity in the robin's role.", "hook": "", "id": 413 },

www/js/interpreter.ts

@@ -201,7 +201,7 @@ function moveAsLowLevelMoves(move: Move, startingPos: Map<DancerIdentity, Semant
     }
   }
 
-  function getPosFor(id: common.ExtendedDancerIdentity) {
+  function getPosFor(id: common.ExtendedDancerIdentity): SemanticPosition & { setOffset: number, lineOffset: number } {
     const basePos = startingPos.get(id.setIdentity)!;
     return {...basePos,
       setOffset: (basePos.setOffset ?? 0) + id.relativeSet,
@@ -231,19 +231,92 @@ function moveAsLowLevelMoves(move: Move, startingPos: Map<DancerIdentity, Semant
     }
   }
 
-  const res = new Map<DancerIdentity, LowLevelMove[]>();
+  function handleMove(dancerFunc: ((arg: { id: DancerIdentity, startPos: SemanticPosition }) => LowLevelMove[])): Map<DancerIdentity, LowLevelMove[]> {
+    const res = new Map<DancerIdentity, LowLevelMove[]>();
+    for (const [id, startPos] of startingPos.entries()) {
+      res.set(id, dancerFunc({ id, startPos }));
+    }
+    return res;
+  }
+
+  function handleCircleMove(dancerFunc: ((arg: { id: DancerIdentity, startPos: SemanticPosition & { kind: PositionKind.Circle } }) => LowLevelMove[])): Map<DancerIdentity, LowLevelMove[]> {
+    return handleMove(({ id, startPos }) => {
+      if (startPos.kind !== PositionKind.Circle) {
+        throw move.move + " must start in a circle, but " + id + " is at " + startPos;
+      }
+
+      return dancerFunc({ id, startPos });
+    });
+  }
+
+  function handlePairedMove(who: chooser_pairz, dancerFunc: ((arg: {
+    id: DancerIdentity,
+    startPos: SemanticPosition,
+    withPos: SemanticPosition & { setOffset: number, lineOffset: number },
+    withId: common.ExtendedDancerIdentity,
+    around: CircleSideOrCenter,
+  }) => LowLevelMove[])): Map<DancerIdentity, LowLevelMove[]> {
+    return handleMove(({ id, startPos }) => {
+      const withId = findPairOpposite(who, id);
+      if (!withId) {
+        return combine([{
+          beats: move.beats,
+          startPosition: { ...startPos, hands: undefined },
+          endPosition: { ...startPos, hands: undefined },
+          movementPattern: { kind: SemanticAnimationKind.StandStill },
+        }]);
+      }
+      const withPos = getPosFor(withId);
+      const setDifference = withPos.setOffset - (startPos.setOffset ?? 0);
+      let startPosAdjusted = startPos;
+      if (setDifference !== 0) {
+        // TODO Can move be with a different short line or just a different circle?
+        //      PassBy can probably be with the next short line...
+        if (startPos.kind === PositionKind.Circle && (setDifference === 1 || setDifference === -1)) {
+          startPosAdjusted = {
+            ...startPos,
+            setOffset: (startPos.setOffset ?? 0) + setDifference / 2,
+            which: startPos.which.swapUpAndDown(),
+          }
+        } else {
+          throw "Not near dancer to " + move.move + " with.";
+        }
+      }
+      const startWhich = startPosAdjusted.which;
+      // TODO Can swing be across the set (top or bottom)?
+      const around = withPos.kind === PositionKind.Circle
+        ? (withPos.which.leftRightSide() === startWhich.leftRightSide()
+          ? startWhich.leftRightSide()
+          : startWhich instanceof CirclePosition && withPos.which.topBottomSide() === startWhich.topBottomSide()
+          ? startWhich.topBottomSide()
+          : "Center")
+        : "Center";
+
+      return dancerFunc({ id, startPos: startPosAdjusted, withId, withPos, around });
+    });
+  }
+
+  function handleCirclePairedMove(who: chooser_pairz, dancerFunc: ((arg: {
+    id: DancerIdentity,
+    startPos: SemanticPosition & { kind: PositionKind.Circle },
+    withPos: SemanticPosition & { setOffset: number, lineOffset: number },
+    withId: common.ExtendedDancerIdentity,
+    around: CircleSideOrCenter,
+  }) => LowLevelMove[])): Map<DancerIdentity, LowLevelMove[]> {
+    return handlePairedMove(who, ({ id, startPos, withId, withPos, around }) => {
+      if (startPos.kind !== PositionKind.Circle) {
+        throw move.move + " must start in a circle, but " + id + " is at " + startPos;
+      }
+
+      return dancerFunc({ id, startPos, withId, withPos, around });
+    });
+  }
+
   switch (move.move) {
     case "balance the ring":
-      for (const [id, startPos] of startingPos.entries()) {
+      return handleCircleMove(({ startPos }) => balanceCircleInAndOut(move, startPos));
-        res.set(id, balanceCircleInAndOut(move, startPos));
-      }
-      return res;
     case "petronella":
-      for (const [id, startPos] of startingPos.entries()) {
+      return handleCircleMove(({ startPos }) => {
-        if (startPos.kind !== PositionKind.Circle) {
-          throw move.move + " must start in a circle, but " + id + " is at " + startPos;
-        }
-
         // TODO These should be actual parameters, not parsing the notes...
         const rightShoulder: boolean = !(move.note?.includes('left') ?? false);
         const newCircle: boolean = move.note?.includes('end facing') ?? false;
@@ -262,52 +335,37 @@ function moveAsLowLevelMoves(move: Move, startingPos: Map<DancerIdentity, Semant
           }
         }
 
+        const spin: ((prevEnd: SemanticPosition) => PartialLowLevelMove) = prevEnd => ({
+          beats: move.beats - (move.parameters.bal ? 4 : 0),
+          startPosition: {
+            ...prevEnd,
+            facing: Facing.CenterOfCircle,
+            hands: undefined,
+          },
+          endPosition: finalPosition,
+          movementPattern: {
+            kind: SemanticAnimationKind.Linear,
+            minRotation: rightShoulder ? 180 : -180,
+            handsDuring: "None",
+          },
+        });
+
         if (move.parameters.bal) {
           const balance: LowLevelMove[] = balanceCircleInAndOut(move, startPos);
-          res.set(id, append([...balance], prevEnd => ({
+          return append([...balance], spin);
-            beats: move.beats - 4,
-            startPosition: {
-              ...prevEnd,
-              hands: undefined,
-            },
-            endPosition: finalPosition,
-            movementPattern: {
-              kind: SemanticAnimationKind.Linear,
-              minRotation: rightShoulder ? 180 : -180,
-              handsDuring: "None",
-            },
-          })));
         } else {
-          res.set(id, combine([{
+          return combine([spin]);
-            beats: move.beats,
-            startPosition: {
-              ...startPos,
-              facing: Facing.CenterOfCircle,
-              hands: undefined,
-            },
-            endPosition: finalPosition,
-            movementPattern: {
-              kind: SemanticAnimationKind.Linear,
-              minRotation: rightShoulder ? 180 : -180,
-              handsDuring: "None",
-            },
-          }]));
         }
-      }
+      });
-      return res;
     case "mad robin":
-      for (const [id, startPos] of startingPos.entries()) {
+      return handleCircleMove(({ startPos }) => {
-        if (startPos.kind !== PositionKind.Circle) {
-          throw move.move + " must start in a circle, but " + id + " is at " + startPos;
-        }
-
         // TODO Read who of mad robin to decide direction?
         const startAndEndPos = {
           ...startPos,
           facing: startPos.which.isLeft() ? Facing.Right : Facing.Left,
           hands: undefined,
         };
-        res.set(id, combine([{
+        return combine([{
           beats: move.beats,
           startPosition: startAndEndPos,
           endPosition: startAndEndPos,
@@ -316,27 +374,10 @@ function moveAsLowLevelMoves(move: Move, startingPos: Map<DancerIdentity, Semant
             amount: move.parameters.circling,
             around: startPos.which.leftRightSide(),
           },
-        }]));
+        }]);
-      }
+      });
-      return res;
     case "do si do":
-      for (const [id, startPos] of startingPos.entries()) {
+      return handleCirclePairedMove(move.parameters.who, ({ startPos, around }) => {
-        if (startPos.kind !== PositionKind.Circle) {
-          throw move.move + " must start in a circle, but " + id + " is at " + startPos;
-        }
-
-        const withId = findPairOpposite(move.parameters.who, id);
-        if (!withId) {
-          res.set(id, combine([{
-            beats: move.beats,
-            startPosition: { ...startPos, hands: undefined },
-            endPosition: { ...startPos, hands: undefined },
-            movementPattern: { kind: SemanticAnimationKind.StandStill },
-          }]));
-          continue;
-        }
-        const around = findCenterBetween(id, withId);
-
         // TODO Use other parameters?
         const startAndEndPos = {
           ...startPos,
@@ -347,7 +388,7 @@ function moveAsLowLevelMoves(move: Move, startingPos: Map<DancerIdentity, Semant
             ? (startPos.which.isTop() ? Facing.Down : Facing.Up)
             : (startPos.which.isLeft() ? Facing.Right : Facing.Left),
         };
-        res.set(id, combine([{
+        return combine([{
           beats: move.beats,
           startPosition: startAndEndPos,
           endPosition: startAndEndPos,
@@ -356,112 +397,66 @@ function moveAsLowLevelMoves(move: Move, startingPos: Map<DancerIdentity, Semant
             amount: move.parameters.circling,
             around,
           },
-        }]));
+        }]);
-      }
+      });
-      return res;
     case "swing":
-      for (const [id, startPos] of startingPos.entries()) {
+      return handleCirclePairedMove(move.parameters.who, ({ id, startPos, around, withId }) => {
-        if (excludedByWho(move.parameters.who, id)) {
+        // TODO swing can start from non-circle positions.
-          res.set(id, combine([{
-            beats: move.beats,
-            startPosition: { ...startPos, hands: undefined },
-            endPosition: { ...startPos, hands: undefined },
-            movementPattern: { kind: SemanticAnimationKind.StandStill },
-          }]));
-          continue;
-        }
-
-        // TODO swing can start from other positions.
         // TODO swing end is only in notes / looking at next move.
-        if (startPos.kind !== PositionKind.Circle) {
-          throw move.move + " must start in a circle, but " + id + " is at " + startPos;
-        }
-
-        switch (move.parameters.who) {
-          case "ladles":
-          case "gentlespoons":
-          case "ones":
-          case "twos":
-            throw "Swing in middle is currently unsupported.";
-          case "first corners":
-          case "second corners":
-            throw "contra corners currently unsupported.";
-          case "same roles":
-            throw "same role swing currently unsupported."
-          case "neighbors":
-          case "partners":
-          case "shadows":
-            // TODO Make sure referenced dancer is using same center.
-            break;
-        }
-
-        const withId = findPairOpposite(move.parameters.who, id);
-        if (!withId) {
-          res.set(id, combine([{
-            beats: move.beats,
-            startPosition: { ...startPos, hands: undefined },
-            endPosition: { ...startPos, hands: undefined },
-            movementPattern: { kind: SemanticAnimationKind.StandStill },
-          }]));
-          continue;
-        }
-        const withPos = getPosFor(withId);
-        const setDifference = withPos.setOffset - (startPos.setOffset ?? 0);
-        let startPosAdjusted = startPos;
-        if (setDifference !== 0) {
-          if (setDifference === 1 || setDifference === -1) {
-            startPosAdjusted = {...startPos,
-              setOffset: (startPos.setOffset ?? 0) + setDifference / 2,
-              which: startPos.which.swapUpAndDown(),
-            }
-          } else {
-            throw "Not near dancer to swing with.";
-          }
-        }
-        const startWhich = startPosAdjusted.which;
-        // TODO Can swing be across the set (top or bottom)?
-        const around = withPos.kind === PositionKind.Circle
-          ? (withPos.which.leftRightSide() === startWhich.leftRightSide()
-            ? startWhich.leftRightSide()
-            : "Center")
-          : "Center";
           
-
+        const startWhich = startPos.which;
         const startPosition: SemanticPosition = {
-          ...startPosAdjusted,
+          ...startPos,
           facing: startWhich.topBottomSide() === CircleSide.Bottom ? Facing.Up : Facing.Down,
         };
+
+        const swingRole = id.danceRole != withId.setIdentity.danceRole
+          ? id.danceRole
+          // Make some arbitrary choice for same-role swings
+          : id.coupleRole !== withId.setIdentity.coupleRole
+          ? (id.coupleRole === CoupleRole.Ones ? DanceRole.Lark : DanceRole.Robin)
+          : withId.relativeSet !== 0
+          ? (withId.relativeSet > 0 ? DanceRole.Lark : DanceRole.Robin)
+          : withId.relativeLine !== 0
+          ? (withId.relativeLine > 0 ? DanceRole.Lark : DanceRole.Robin)
+          : /* should be unreachable as this means withId is equal to id */ DanceRole.Lark;
+
+        // TODO This assumes swing around right/left, not center or top/bottom.
         const endPosition: SemanticPosition = {
-          ...startPosAdjusted,
+          ...startPos,
-          which: startWhich.isOnLeftLookingAcross() === (id.danceRole === DanceRole.Lark)
+          which: startWhich.isOnLeftLookingAcross() === (swingRole === DanceRole.Lark)
             ? startWhich
             : startWhich.swapUpAndDown(),
           facing: startWhich.leftRightSide() === CircleSide.Left ? Facing.Right : Facing.Left,
           balance: undefined,
           dancerDistance: undefined,
-          hands: new Map<Hand, HandConnection>([id.danceRole === DanceRole.Lark
+          hands: new Map<Hand, HandConnection>([swingRole === DanceRole.Lark
             ? [Hand.Right, { to: HandTo.DancerRight, hand: Hand.Left }]
             : [Hand.Left, { to: HandTo.DancerLeft, hand: Hand.Right }]]),
         };
-        // TODO same role swing currently unsupported.
+
-        const swingRole = id.danceRole === DanceRole.Lark ? DancerDistance.SwingLark : DancerDistance.SwingRobin;
+        const swingBeats = move.parameters.prefix === "none" ? move.beats
+          : move.parameters.prefix === "balance"
+            ? move.beats > 8 ? 8 : move.beats - 4
+            : move.parameters.prefix === "meltdown"
+              ? move.beats - 4
+              : (() => { throw "Unknown swing prefix: " + move.parameters.prefix })();
+
+        const swing: PartialLowLevelMove = {
+          beats: swingBeats,
+          endPosition: endPosition,
+          movementPattern: {
+            kind: SemanticAnimationKind.Swing,
+            minAmount: 360,
+            around,
+            endFacing: startWhich.leftRightSide() === CircleSide.Left ? Facing.Right : Facing.Left,
+            swingRole,
+          },
+        };
 
         switch (move.parameters.prefix) {
           case "none":
-            res.set(id, combine([
+            return combine([swing,], startPosition);
-              {
-                beats: move.beats,
-                endPosition: endPosition,
-                movementPattern: {
-                  kind: SemanticAnimationKind.Swing,
-                  minAmount: 360,
-                  around,
-                  endFacing: startWhich.leftRightSide() === CircleSide.Left ? Facing.Right : Facing.Left,
-                  swingRole: id.danceRole,
-                },
-              },
-            ], startPosition));
-            break;
           case "balance":
             // TODO Right length for balance?
             const balancePartBeats = move.beats > 8 ? (move.beats - 8) / 2 : 2;
@@ -472,7 +467,7 @@ function moveAsLowLevelMoves(move: Move, startingPos: Map<DancerIdentity, Semant
                 [Hand.Right, { to: HandTo.DancerForward, hand: Hand.Left }],
               ]),
             };
-            res.set(id, combine([
+            return combine([
               {
                 beats: balancePartBeats,
                 startPosition: startWithBalHands,
@@ -491,22 +486,11 @@ function moveAsLowLevelMoves(move: Move, startingPos: Map<DancerIdentity, Semant
                 },
                 movementPattern: { kind: SemanticAnimationKind.Linear, },
               }),
-              {
+              swing,
-                beats: move.beats - 2 * balancePartBeats,
+            ], startPosition);
-                endPosition: endPosition,
-                movementPattern: {
-                  kind: SemanticAnimationKind.Swing,
-                  minAmount: 360,
-                  around,
-                  endFacing: startWhich.leftRightSide() === CircleSide.Left ? Facing.Right : Facing.Left,
-                  swingRole: id.danceRole,
-                },
-              },
-            ], startPosition));
-            break;
           case "meltdown":
             const meltdownBeats = 4; // TODO right number here?
-            res.set(id, combine([
+            return combine([
               prevEnd => ({
                 beats: meltdownBeats,
                 endPosition: prevEnd,
@@ -517,52 +501,19 @@ function moveAsLowLevelMoves(move: Move, startingPos: Map<DancerIdentity, Semant
                   byHand: undefined,
                 },
               }),
-              {
+              swing,
-                beats: move.beats - meltdownBeats,
+            ], startPosition);
-                endPosition: endPosition,
-                movementPattern: {
-                  kind: SemanticAnimationKind.Swing,
-                  minAmount: 360,
-                  around,
-                  endFacing: startWhich.leftRightSide() === CircleSide.Left ? Facing.Right : Facing.Left,
-                  swingRole: id.danceRole,
-                },
-              },
-            ], startPosition));
-            break;
         }
-      }
+      });
-      return res;
 
     case "allemande":
     case "gyre":
-      for (const [id, startPos] of startingPos.entries()) {
+      return handlePairedMove(move.parameters.who, ({ startPos, around, withId }) => {
-        if (excludedByWho(move.parameters.who, id)) {
-          res.set(id, combine([{
-            beats: move.beats,
-            startPosition: { ...startPos, hands: undefined },
-            endPosition: { ...startPos, hands: undefined },
-            movementPattern: { kind: SemanticAnimationKind.StandStill },
-          }]));
-          continue;
-        }
-
-        // TODO allemande can start from other positions.
-        if (startPos.kind !== PositionKind.Circle) {
-          throw move.move + " must start in a circle, but " + id + " is at " + startPos;
-        }
-
-        const withId = findPairOpposite(move.parameters.who, id);
-        // findPairOpposite of null means this dancer doesn't participate in this move.
-        if (!withId) {
-          throw "fairPairOpposite and excludedByWho disagree on who does not act: who=" + move.parameters.who + ", id=" + id;
-        }
-        const around = findCenterBetween(id, withId);
-
         // TODO Not sure if this is right.
         const byHandOrShoulder = (move.move === "allemande" ? move.parameters.hand : move.parameters.shoulder) ? Hand.Right : Hand.Left;
         const swap = move.parameters.circling % 360 === 180;
         if (!swap && move.parameters.circling % 360 !== 0) {
+          // TODO Support allemande that's not a swap or no-op.
           throw "Unsupported allemande circle amount: " + move.parameters.circling;
         }
         let endPosition : SemanticPosition = startPos;
@@ -572,7 +523,7 @@ function moveAsLowLevelMoves(move: Move, startingPos: Map<DancerIdentity, Semant
           endPosition.lineOffset = (endPosition.lineOffset ?? 0) + withId.relativeLine;
         }
 
-        res.set(id, combine([
+        return combine([
           {
             beats: move.beats,
             endPosition,
@@ -583,20 +534,14 @@ function moveAsLowLevelMoves(move: Move, startingPos: Map<DancerIdentity, Semant
               byHand: move.move === "allemande" ? byHandOrShoulder : undefined,
             },
           },
-        ], startPos));
+        ], startPos);
-      }
+      });
-
-      return res;
 
     case "circle":
-      const places = move.parameters.places/90 * (move.parameters.turn ? 1 : -1);
+      return handleCircleMove(({ startPos }) => {
+        const places = move.parameters.places / 90 * (move.parameters.turn ? 1 : -1);
 
-      for (const [id, startPos] of startingPos.entries()) {
+        return combine([
-        if (startPos.kind !== PositionKind.Circle) {
-          throw move.move + " must start in a circle, but " + id + " is at " + startPos;
-        }
-
-        res.set(id, combine([
           {
             beats: move.beats,
             endPosition: {
@@ -610,32 +555,16 @@ function moveAsLowLevelMoves(move: Move, startingPos: Map<DancerIdentity, Semant
               places,
             }
           },
-        ], { ...startPos, facing: Facing.CenterOfCircle }));
+        ], { ...startPos, facing: Facing.CenterOfCircle });
-      }
+      });
-
-      return res;
 
     case "California twirl":
-      for (const [id, startPos] of startingPos.entries()) {
+      return handleCirclePairedMove(move.parameters.who, ({ startPos }) => {
-        if (excludedByWho(move.parameters.who, id)) {
-          res.set(id, combine([{
-            beats: move.beats,
-            startPosition: { ...startPos, hands: undefined },
-            endPosition: { ...startPos, hands: undefined },
-            movementPattern: { kind: SemanticAnimationKind.StandStill },
-          }]));
-          continue;
-        }
-
-        if (startPos.kind !== PositionKind.Circle) {
-          throw move.move + " must start in a circle, but " + id + " is at " + startPos;
-        }
-
         // TODO does "who" matter here or is it entirely positional? At least need to know who to omit.
 
         const onLeft : boolean = startPos.which.isOnLeftLookingUpAndDown();
         // TODO get rid of this 1 beat set up and make it part of TwirlSwap?
-        res.set(id, combine([
+        return combine([
           {
             beats: 1,
             endPosition: {
@@ -661,23 +590,11 @@ function moveAsLowLevelMoves(move: Move, startingPos: Map<DancerIdentity, Semant
               around: startPos.which.topBottomSide(),
               hand: onLeft ? Hand.Right : Hand.Left,
             }
-          }], startPos));
+          }], startPos);
-      }
+      });
-
-      return res;
 
     case "box the gnat":
-      for (const [id, startPos] of startingPos.entries()) {
+      return handlePairedMove(move.parameters.who, ({ startPos, around, withPos }) => {
-        if (excludedByWho(move.parameters.who, id)) {
-          res.set(id, combine([{
-            beats: move.beats,
-            startPosition: { ...startPos, hands: undefined },
-            endPosition: { ...startPos, hands: undefined },
-            movementPattern: { kind: SemanticAnimationKind.StandStill },
-          }]));
-          continue;
-        }
-
         const hand = move.parameters.hand ? Hand.Right : Hand.Left;
         const balanceBeats = move.parameters.bal
           ? move.beats > 4
@@ -690,18 +607,22 @@ function moveAsLowLevelMoves(move: Move, startingPos: Map<DancerIdentity, Semant
         // TODO Adjust facing?
         const startPosition = { ...startPos, hands: new Map<Hand, HandConnection>([[hand, { hand, to: HandTo.DancerForward }]]) };
 
-        const withId = findPairOpposite(move.parameters.who, id);
-        // findPairOpposite of null means this dancer doesn't participate in this move.
-        if (!withId) {
-          throw "fairPairOpposite and excludedByWho disagree on who does not act: who=" + move.parameters.who + ", id=" + id;
-        }
-        const around = findCenterBetween(id, withId);
         if (around === "Center") {
           throw "TwirlSwap around center is unsupported.";
         }
 
+        const twirl: PartialLowLevelMove = {
+          beats: twirlBeats,
+          endPosition: withPos,
+          movementPattern: {
+            kind: SemanticAnimationKind.TwirlSwap,
+            around,
+            hand,
+          }
+        };
+
         if (move.parameters.bal) {
-          res.set(id, combine([
+          return combine([
             {
               beats: balancePartBeats,
               endPosition: {
@@ -722,43 +643,14 @@ function moveAsLowLevelMoves(move: Move, startingPos: Map<DancerIdentity, Semant
                 kind: SemanticAnimationKind.Linear,
               }
             },
-            {
+            twirl], startPosition);
-              beats: twirlBeats,
-              endPosition: getPosFor(withId),
-              movementPattern: {
-                kind: SemanticAnimationKind.TwirlSwap,
-                around,
-                hand,
-              }
-            }], startPosition));
         } else {
-          res.set(id, combine([
+          return combine([twirl], startPosition);
-            {
-              beats: twirlBeats,
-              endPosition: getPosFor(withId),
-              movementPattern: {
-                kind: SemanticAnimationKind.TwirlSwap,
-                around,
-                hand,
-              }
-            }], startPosition));
         }
-      }
+      });
-
-      return res;
 
     case "pull by dancers":
-      for (const [id, startPos] of startingPos.entries()) {
+      return handlePairedMove(move.parameters.who, ({ startPos, around, withPos }) => {
-        if (excludedByWho(move.parameters.who, id)) {
-          res.set(id, combine([{
-            beats: move.beats,
-            startPosition: { ...startPos, hands: undefined },
-            endPosition: { ...startPos, hands: undefined },
-            movementPattern: { kind: SemanticAnimationKind.StandStill },
-          }]));
-          continue;
-        }
-
         const hand = move.parameters.hand ? Hand.Right : Hand.Left;
         const balanceBeats = move.parameters.bal
           ? move.beats > 4
@@ -768,13 +660,6 @@ function moveAsLowLevelMoves(move: Move, startingPos: Map<DancerIdentity, Semant
         const balancePartBeats = balanceBeats / 2;
         const pullBeats = move.beats - balanceBeats;
 
-        const withId = findPairOpposite(move.parameters.who, id);
-        // findPairOpposite of null means this dancer doesn't participate in this move.
-        if (!withId) {
-          throw "fairPairOpposite and excludedByWho disagree on who does not act: who=" + move.parameters.who + ", id=" + id;
-        }
-        const around = findCenterBetween(id, withId);
-
         // TODO Adjust facing?
         const startPosition = {
           ...startPos,
@@ -785,9 +670,19 @@ function moveAsLowLevelMoves(move: Move, startingPos: Map<DancerIdentity, Semant
             ]])
         };
 
+        const passBy: PartialLowLevelMove = {
+          beats: pullBeats,
+          endPosition: { ...withPos, facing: startPos.facing },
+          movementPattern: {
+            kind: SemanticAnimationKind.PassBy,
+            around,
+            side: hand,
+            withHands: true,
+          }
+        };
 
         if (move.parameters.bal) {
-          res.set(id, combine([
+          return combine([
             {
               beats: balancePartBeats,
               endPosition: {
@@ -808,43 +703,18 @@ function moveAsLowLevelMoves(move: Move, startingPos: Map<DancerIdentity, Semant
                 kind: SemanticAnimationKind.Linear,
               }
             },
-            {
+            passBy], startPosition);
-              beats: pullBeats,
-              endPosition: getPosFor(withId),
-              movementPattern: {
-                kind: SemanticAnimationKind.PassBy,
-                around,
-                side: hand,
-                withHands: true,
-              }
-            }], startPosition));
         } else {
-          res.set(id, combine([
+          return combine([passBy], startPosition);
-            {
-              beats: pullBeats,
-              endPosition: getPosFor(withId),
-              movementPattern: {
-                kind: SemanticAnimationKind.PassBy,
-                around,
-                side: hand,
-                withHands: true,
-              }
-            }], startPosition));
         }
-      }
+      });
-
-      return res;
 
     case "chain":
-      for (const [id, startPos] of startingPos.entries()) {
+      const mainRole = move.parameters.who === "gentlespoons" ? DanceRole.Lark : DanceRole.Robin;
-        if (startPos.kind !== PositionKind.Circle) {
+      const pullBeats = move.beats / 2;
-          throw move.move + " must start in a circle, but " + id + " is at " + startPos;
+      const turnBeats = move.beats - pullBeats;
-        }
-
-        const mainRole = move.parameters.who === "gentlespoons" ? DanceRole.Lark : DanceRole.Robin;
-        const pullBeats = move.beats / 2;
-        const turnBeats = move.beats - pullBeats;
 
+      return handleCircleMove(({ id, startPos }) => {
         if (id.danceRole === mainRole) {
           const hand = move.parameters.hand ? Hand.Right : Hand.Left;
           const endWhich = startPos.which.swapDiagonal();
@@ -869,7 +739,7 @@ function moveAsLowLevelMoves(move: Move, startingPos: Map<DancerIdentity, Semant
 
           const turnTo = hand === Hand.Right ? HandTo.DancerRight : HandTo.DancerLeft;
 
-          res.set(id, combine([
+          return combine([
             {
               beats: pullBeats,
               endPosition: {
@@ -902,9 +772,9 @@ function moveAsLowLevelMoves(move: Move, startingPos: Map<DancerIdentity, Semant
                 kind: SemanticAnimationKind.CourtesyTurn,
               }
             })
-          ], startPosition));
+          ], startPosition);
         } else {
-          res.set(id, combine([
+          return combine([
             {
               beats: pullBeats,
               endPosition: startPos,
@@ -923,18 +793,12 @@ function moveAsLowLevelMoves(move: Move, startingPos: Map<DancerIdentity, Semant
                 kind: SemanticAnimationKind.CourtesyTurn,
               }
             }
-          ], startPos));
+          ], startPos);
         }
-      }
+      });
-
-      return res;
 
     case "long lines":
-      for (const [id, startPos] of startingPos.entries()) {
+      return handleCircleMove(({ startPos }) => {
-        if (startPos.kind !== PositionKind.Circle) {
-          throw move.move + " must start in a circle, but " + id + " is at " + startPos;
-        }
-
         const startPosition: SemanticPosition = {
           ...startPos,
           longLines: undefined,
@@ -949,7 +813,7 @@ function moveAsLowLevelMoves(move: Move, startingPos: Map<DancerIdentity, Semant
         if (move.parameters.go) {
           const forwardBeats = move.beats / 2;
           const backwardBeats = move.beats - forwardBeats;
-          res.set(id, combine([
+          return combine([
             {
               beats: forwardBeats,
               endPosition: { ...startPosition, longLines: LongLines.Forward },
@@ -960,24 +824,19 @@ function moveAsLowLevelMoves(move: Move, startingPos: Map<DancerIdentity, Semant
               endPosition: startPosition,
               movementPattern: { kind: SemanticAnimationKind.Linear },
             },
-          ], startPosition));
+          ], startPosition);
         } else {
-          res.set(id, combine([{
+          return combine([{
             beats: move.beats,
             endPosition: { ...startPosition, longLines: LongLines.Forward },
             movementPattern: { kind: SemanticAnimationKind.Linear },
-          }], startPosition));
+          }], startPosition);
         }
-      }
+      });
-
-      return res;
 
     case "roll away":
-      for (const [id, startPos] of startingPos.entries()) {
+      // TODO maybe can roll away in short lines?
-        if (startPos.kind !== PositionKind.Circle) {
+      return handleCirclePairedMove(move.parameters.who, ({ id, startPos, withPos }) => {
-          throw move.move + " must start in a circle, but " + id + " is at " + startPos;
-        }
-
         let isRoller: boolean;
         switch (move.parameters.who) {
           case "gentlespoons":
@@ -997,15 +856,8 @@ function moveAsLowLevelMoves(move: Move, startingPos: Map<DancerIdentity, Semant
             throw "Roll away in contra corners is unsupported.";
         }
 
-        let oppositeId = findPairOpposite(move.parameters.whom, id);
-        if (!oppositeId) {
-          // TODO
-          throw "Failed to identify dancer to roll away with.";
-        }
-
         // TODO This isn't quite right if there's no 1/2 sash?
-        const oppositePos = getPosFor(oppositeId);
+        let swapPos = withPos;
-        let swapPos = oppositePos;
         if (swapPos.kind === PositionKind.Circle && swapPos.longLines) {
           swapPos = { ...swapPos, longLines: undefined };
         }
@@ -1014,37 +866,35 @@ function moveAsLowLevelMoves(move: Move, startingPos: Map<DancerIdentity, Semant
         if (isRoller) {
           if (move.parameters["½sash"]) {
             // swap positions by sliding
-            res.set(id, combine([{
+            return combine([{
               beats: move.beats,
               endPosition: swapPos,
               movementPattern: { kind: SemanticAnimationKind.Linear },
-            }], startPos));
+            }], startPos);
           } else {
             // just stand still
-            res.set(id, combine([{
+            return combine([{
               beats: move.beats,
               endPosition: { ...startPos, longLines: undefined },
               movementPattern: { kind: SemanticAnimationKind.Linear },
-            }], startPos));
+            }], startPos);
           }
         } else {
           // being rolled away, so do a spin
-          res.set(id, combine([{
+          return combine([{
             beats: move.beats,
             // TODO Is this the right end position logic?
             endPosition: move.parameters["½sash"] ? swapPos : { ...startPos, which: startPos.which.swapDiagonal() },
             movementPattern: { kind: SemanticAnimationKind.RollAway },
-          }], startPos));
+          }], startPos);
         }
-      }
+      });
-
-      return res;
   }
 
   // XXX DEBUG Just leave out unsupported moves for now to allow viewing the known moves.
   //throw "Unknown move: " + move.move + ": " + JSON.stringify(move);
-  for (const [id, startPos] of startingPos.entries()) {
+  return handleMove(({ startPos }) => {
-    res.set(id, [{
+    return [{
       interpreterError: "UNKNOWN MOVE '" + move.move + "': standing still",
       move,
       startBeat: 0,
@@ -1054,9 +904,8 @@ function moveAsLowLevelMoves(move: Move, startingPos: Map<DancerIdentity, Semant
       movementPattern: {
         kind: SemanticAnimationKind.StandStill,
       },
-    }]);
+    }];
-  }
+  });
-  return res;
 }
 
 function danceAsLowLevelMoves(moves: Move[], startingPos: Map<DancerIdentity, SemanticPosition>): Map<DancerIdentity, LowLevelMove[]> {