1 files changed, 29 insertions, 0 deletions
diff --git a/lib/libF77/z_sqrt.c b/lib/libF77/z_sqrt.c
new file mode 100644
index 000000000000..eed38d0cef85
--- /dev/null
+++ b/lib/libF77/z_sqrt.c
@@ -0,0 +1,29 @@
+#include "f2c.h"
+
+#ifdef KR_headers
+double sqrt(), f__cabs();
+VOID z_sqrt(r, z) doublecomplex *r, *z;
+#else
+#undef abs
+#include "math.h"
+extern double f__cabs(double, double);
+void z_sqrt(doublecomplex *r, doublecomplex *z)
+#endif
+{
+double mag;
+
+if( (mag = f__cabs(z->r, z->i)) == 0.)
+	r->r = r->i = 0.;
+else if(z->r > 0)
+	{
+	r->r = sqrt(0.5 * (mag + z->r) );
+	r->i = z->i / r->r / 2;
+	}
+else
+	{
+	r->i = sqrt(0.5 * (mag - z->r) );
+	if(z->i < 0)
+		r->i = - r->i;
+	r->r = z->i / r->i / 2;
+	}
+}