From 4dd33aa4d5c57706c7f64f63391174954160a308 Mon Sep 17 00:00:00 2001
From: Krzysztof Kosi??ski <tweenk.pl@gmail.com>
Date: Sat, 6 Aug 2011 14:18:32 +0200
Subject: Rewrite NRArenaItem hierarchy into C++

(bzr r10347.1.21)
---
 src/2geom/affine.cpp | 12 ++++++++++++
 1 file changed, 12 insertions(+)

(limited to 'src/2geom/affine.cpp')

diff --git a/src/2geom/affine.cpp b/src/2geom/affine.cpp
index 2a1f18d77..c31b9ba90 100644
--- a/src/2geom/affine.cpp
+++ b/src/2geom/affine.cpp
@@ -410,6 +410,9 @@ Affine &Affine::operator*=(Affine const &o) {
 }
 
 //TODO: What's this!?!
+/** Given a matrix m such that unit_circle = m*x, this returns the
+ * quadratic form x*A*x = 1.
+ * @relates Affine */
 Affine elliptic_quadratic_form(Affine const &m) {
     double od = m[0] * m[1]  +  m[2] * m[3];
     Affine ret (m[0]*m[0] + m[1]*m[1], od,
@@ -469,6 +472,15 @@ Eigen::Eigen(double m[2][2]) {
         vectors[i] = Point(0,0);
 }
 
+/** @brief Nearness predicate for affine transforms
+ * @returns True if all entries of matrices are within eps of each other */
+bool are_near(Affine const &a, Affine const &b, Coord eps)
+{
+    return are_near(a[0], b[0], eps) && are_near(a[1], b[1], eps) &&
+           are_near(a[2], b[2], eps) && are_near(a[3], b[3], eps) &&
+           are_near(a[4], b[4], eps) && are_near(a[5], b[5], eps);
+}
+
 }  //namespace Geom
 
 /*
-- 
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