[gegl] matrix: add gegl_matrix2_determinant()

[N/A <ell src gnome org>]

commit ea05b209f116afa680bcafcf6164181f74800de9
Author: Ell <ell_se yahoo com>
Date:   Sat Mar 3 02:46:58 2018 -0500

    matrix: add gegl_matrix2_determinant()
    
    ... which calculates the determinant of a GeglMatrix2.

 gegl/gegl-matrix.c |    7 +++++++
 gegl/gegl-matrix.h |    8 ++++++++
 2 files changed, 15 insertions(+), 0 deletions(-)
---
diff --git a/gegl/gegl-matrix.c b/gegl/gegl-matrix.c
index 119f230..98a0864 100644
--- a/gegl/gegl-matrix.c
+++ b/gegl/gegl-matrix.c
@@ -24,6 +24,13 @@
 #include "gegl-matrix.h"
 
 
+gdouble
+gegl_matrix2_determinant (GeglMatrix2 *matrix)
+{
+  return matrix->coeff[0][0] * matrix->coeff[1][1] -
+         matrix->coeff[1][0] * matrix->coeff[0][1];
+}
+
 #if 0
 static void gegl_matrix3_debug (GeglMatrix3 *matrix)
 {
diff --git a/gegl/gegl-matrix.h b/gegl/gegl-matrix.h
index f1763ea..b080a1f 100644
--- a/gegl/gegl-matrix.h
+++ b/gegl/gegl-matrix.h
@@ -32,6 +32,14 @@ typedef struct {
     gdouble coeff[2][2];
 } GeglMatrix2;
 
+/**
+ * gegl_matrix2_determinant:
+ * @matrix: a #GeglMatrix2
+ *
+ * Returns the determinant of @matrix.
+ */
+gdouble    gegl_matrix2_determinant     (GeglMatrix2 *matrix);
+
 /***
  * GeglMatrix3:
  *