diff --git a/modules/brep/io/brepLoopsFormat.js b/modules/brep/io/brepLoopsFormat.ts
similarity index 65%
rename from modules/brep/io/brepLoopsFormat.js
rename to modules/brep/io/brepLoopsFormat.ts
index 2fcf7aab..ddc86dca 100644
--- a/modules/brep/io/brepLoopsFormat.js
+++ b/modules/brep/io/brepLoopsFormat.ts
@@ -1,7 +1,18 @@
+import {Loop} from "brep/topo/loop";
+import {Shell} from "brep/topo/shell";
+import {Vec3} from "math/vec";
+import {Vertex} from "brep/topo/vertex";
 
-export function toLoops(shell, presicion) {
+export interface BREPLoopsFormat {
+  format: 'LOOPS';
+  vertices: Vec3[];
+  faces: number[][];
 
-  const fl = presicion || (v => v);
+}
+
+export function toLoops(shell: Shell, precisionFn: (number) => number): BREPLoopsFormat {
+
+  const fl = precisionFn || (v => v);
   
   const vertices = [];
   for (let v of shell.vertices) {
@@ -29,7 +40,7 @@ export function toLoops(shell, presicion) {
   };
 }
 
-function sortByXYZ(vertices) {
+function sortByXYZ(vertices: Vertex[]) {
   vertices.sort((v1, v2) => {
     let c = v1.point.x - v2.point.x;
     if (c === 0) {
diff --git a/modules/brep/topo/face.ts b/modules/brep/topo/face.ts
index 2ab2e4a7..5c11e9e9 100644
--- a/modules/brep/topo/face.ts
+++ b/modules/brep/topo/face.ts
@@ -4,8 +4,9 @@ import PIP from '../../../web/app/cad/tess/pip';
 import {veq} from "geom/tolerance";
 import {isOnPositiveHalfPlaneFromVec} from "../operations/boolean";
 import {BrepSurface} from "geom/surfaces/brepSurface";
-import {Shell} from "./shell";
+import {edgesGenerator, Shell} from "./shell";
 import {ProductionInfo} from "../../../web/app/cad/craft/engine/productionInfo";
+import {HalfEdge} from "brep/topo/edge";
 
 declare module './face' {
 
@@ -35,14 +36,20 @@ export class Face extends TopoObject {
   innerLoops: Loop[];
   private __2d: any;
 
+  loops = {
+    [Symbol.iterator]: () => loopsGenerator(this)
+  };
+  edges = {
+    [Symbol.iterator]: () => halfEdgesGenerator(this)
+  };
+
+
   constructor(surface: BrepSurface) {
     super();
     this.surface = surface;
     this.shell = null;
     this.outerLoop = new Loop(this);
     this.innerLoops = [];
-    this.defineIterable('loops', () => loopsGenerator(this));
-    this.defineIterable('edges', () => halfEdgesGenerator(this));
   }
 
   get id(): string {
@@ -153,7 +160,7 @@ export class Face extends TopoObject {
   }
 }
 
-export function* loopsGenerator(face) {
+export function* loopsGenerator(face): Generator<Loop> {
   if (face.outerLoop !== null) {
     yield face.outerLoop;
   }
@@ -162,7 +169,7 @@ export function* loopsGenerator(face) {
   }
 }
 
-export function* halfEdgesGenerator(face) {
+export function* halfEdgesGenerator(face): Generator<HalfEdge> {
   for (let loop of face.loops) {
     for (let halfEdge of loop.halfEdges) {
       yield halfEdge;
diff --git a/modules/brep/topo/loop.ts b/modules/brep/topo/loop.ts
index dc596d43..bfcd0c27 100644
--- a/modules/brep/topo/loop.ts
+++ b/modules/brep/topo/loop.ts
@@ -3,19 +3,21 @@ import {Face} from "./face";
 import {BrepSurface} from "geom/surfaces/brepSurface";
 import {HalfEdge} from "./edge";
 import {findLowestLeftPoint} from "geom/euclidean";
+import {Vertex} from "brep/topo/vertex";
 
 export class Loop extends TopoObject {
 
   face: Face;
   halfEdges: HalfEdge[];
-  encloses: any;
+
+  encloses = {
+    [Symbol.iterator]: () => enclosesGenerator(this.halfEdges)
+  };
 
   constructor(face: Face) {
     super();
     this.face = face;
     this.halfEdges = [];
-    this.encloses = undefined;
-    this.defineIterable('encloses', () => enclosesGenerator(this.halfEdges));
   }
 
   isCCW(surface: BrepSurface) {
@@ -68,7 +70,7 @@ export class Loop extends TopoObject {
   };
 }
 
-export function* enclosesGenerator(halfEdges) {
+export function* enclosesGenerator(halfEdges): Generator<[HalfEdge, HalfEdge, Vertex]> {
   let length = halfEdges.length;
   for (let i = 0; i < halfEdges.length; i++) {
     let j = (i + 1) % length;
diff --git a/modules/brep/topo/shell.ts b/modules/brep/topo/shell.ts
index f63cb0fc..f9c0f6cd 100644
--- a/modules/brep/topo/shell.ts
+++ b/modules/brep/topo/shell.ts
@@ -1,20 +1,27 @@
 import {TopoObject} from './topo-object'
 import {Face} from "./face";
 import {Loop} from "./loop";
-import {Edge} from "./edge";
+import {Vertex} from "brep/topo/vertex";
+import {Edge} from "brep/topo/edge";
+
 
 export class Shell extends TopoObject {
 
   faces: Face[];
-  edges: Edge[];
+
+  vertices = {
+    [Symbol.iterator]: () => verticesGenerator(this)
+  };
+
+  edges = {
+    [Symbol.iterator]: () => edgesGenerator(this.faces)
+  };
 
   constructor() {
     super();
     this.faces = [];
-    this.defineIterable('vertices', () => verticesGenerator(this));
-    this.defineIterable('edges', () => edgesGenerator(this.faces))
   }
-  
+
   clone(): Shell {
     let edgeClones = new Map();
     for (let e of this.edges) {
@@ -48,7 +55,7 @@ export class Shell extends TopoObject {
   }
 }
 
-export function* verticesGenerator(shell: Shell) {
+export function* verticesGenerator(shell: Shell): Generator<Vertex> {
   const seen = new Set();
   for (let face of shell.faces) {
     for (let edge of face.edges) {
@@ -60,7 +67,7 @@ export function* verticesGenerator(shell: Shell) {
   }
 }
 
-export function* edgesGenerator(faces: Face[]) {
+export function* edgesGenerator(faces: Face[]): Generator<Edge> {
   const visited = new Set();
   for (let face of faces) {
     for (let halfEdge of face.edges) {
diff --git a/modules/brep/topo/topo-object.ts b/modules/brep/topo/topo-object.ts
index c0fff075..74d8d473 100644
--- a/modules/brep/topo/topo-object.ts
+++ b/modules/brep/topo/topo-object.ts
@@ -13,10 +13,6 @@ export class TopoObject {
     });
   }
   
-  defineIterable(name, iteratorFactory) {
-    this[name] = {};
-    this[name][Symbol.iterator] = iteratorFactory;
-  }
 }
 
 export type OperationTemporaryData = any;