1 files changed, 85 insertions, 0 deletions
diff --git a/gsl-1.9/poly/solve_quadratic.c b/gsl-1.9/poly/solve_quadratic.c
new file mode 100644
index 0000000..8af69db
--- /dev/null
+++ b/gsl-1.9/poly/solve_quadratic.c
@@ -0,0 +1,85 @@
+/* poly/solve_quadratic.c
+ * 
+ * Copyright (C) 1996, 1997, 1998, 1999, 2000 Brian Gough
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or (at
+ * your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+/* solve_quadratic.c - finds the real roots of a x^2 + b x + c = 0 */
+
+#include <config.h>
+#include <math.h>
+
+#include <gsl/gsl_poly.h>
+
+int 
+gsl_poly_solve_quadratic (double a, double b, double c, 
+                          double *x0, double *x1)
+{
+  double disc = b * b - 4 * a * c;
+
+  if (a == 0) /* Handle linear case */
+    {
+      if (b == 0)
+        {
+          return 0;
+        }
+      else
+        {
+          *x0 = -c / b;
+          return 1;
+        };
+    }
+
+  if (disc > 0)
+    {
+      if (b == 0)
+        {
+          double r = fabs (0.5 * sqrt (disc) / a);
+          *x0 = -r;
+          *x1 =  r;
+        }
+      else
+        {
+          double sgnb = (b > 0 ? 1 : -1);
+          double temp = -0.5 * (b + sgnb * sqrt (disc));
+          double r1 = temp / a ;
+          double r2 = c / temp ;
+
+          if (r1 < r2) 
+            {
+              *x0 = r1 ;
+              *x1 = r2 ;
+            } 
+          else 
+            {
+              *x0 = r2 ;
+              *x1 = r1 ;
+            }
+        }
+      return 2;
+    }
+  else if (disc == 0) 
+    {
+      *x0 = -0.5 * b / a ;
+      *x1 = -0.5 * b / a ;
+      return 2 ;
+    }
+  else
+    {
+      return 0;
+    }
+}
+