move basisVector() to member function

Example/Tests/BasisVectorSpec.swift

@@ -13,7 +13,6 @@ class BasisSpec: QuickSpec {
             )
         )
 
-
         context("multiply adj by vector") {
             it("should match expected") {
                 let adjM = float3x3([-122, -152, 18544, 122, 0, 0, 0, 152, 0])
@@ -27,13 +26,13 @@ class BasisSpec: QuickSpec {
         context("basis") {
             it("should match fiddle") {
                 let startBasis = normalize(float3x3([0, 2818688, 0, 0, 0, 2262368, -18544, 18544, 18544]))
-                let result = basis(start)
+                let result = start.basisVector()
                 expect(result) ≈ startBasis ± 0.5
             }
 
             it("should work for destination") {
                 let destBasis = normalize(float3x3([-4000000, 12000000, 4000000, -4000000, 4000000, 12000000, -40000, 40000, 40000]))
-                let result = basis(destination)
+                let result = destination.basisVector()
                 expect(result) ≈ destBasis ± 0.5
             }
         }

Pod/Classes/Quadrilateral+Transform.swift

@@ -10,10 +10,19 @@ import UIKit
 import simd
 
 public extension Quadrilateral {
+    func basisVector() -> float3x3 {
+        let m = first3(self)
+        let v4 = float3(p4)
+        let v = m.inverse * v4
+        let diag = float3x3(diagonal: v)
+        let result = m * diag
+        return result
+    }
+
     func general2DProjection(to:Quadrilateral) -> float3x3 {
-        var source = basis(self)
+        var source = basisVector()
         source = normalize(source)
-        var destination = basis(to)
+        var destination = to.basisVector()
         destination = normalize(destination)
         var result = destination * source.inverse
         result = normalize(result)
@@ -80,15 +89,6 @@ func first3(quad:Quadrilateral) -> float3x3 {
     return float3x3([v1, v2, v3])
 }
 
-func basis(quad:Quadrilateral) -> float3x3 {
-    let m = first3(quad)
-    let v4 = float3(quad.p4)
-    let v = m.inverse * v4
-    let diag = float3x3(diagonal: v)
-    let result = m * diag
-    return result
-}
-
 func normalize(input:float3x3) -> float3x3 {
     return (Float(1) / input[2,2]) * input
 }