1 files changed, 36 insertions, 0 deletions
diff --git a/Tests/Tutorial/Step4/MathFunctions/mysqrt.cxx b/Tests/Tutorial/Step4/MathFunctions/mysqrt.cxx
new file mode 100644
index 0000000..6ca264f
--- /dev/null
+++ b/Tests/Tutorial/Step4/MathFunctions/mysqrt.cxx
@@ -0,0 +1,36 @@
+#include "MathFunctions.h"
+#include "TutorialConfig.h"
+#include <stdio.h>
+
+#include <math.h>
+
+// a hack square root calculation using simple operations
+double mysqrt(double x)
+{
+  if (x <= 0) {
+    return 0;
+  }
+
+  double result;
+
+// if we have both log and exp then use them
+#if defined(HAVE_LOG) && defined(HAVE_EXP)
+  result = exp(log(x) * 0.5);
+  fprintf(stdout, "Computing sqrt of %g to be %g using log\n", x, result);
+#else
+  double delta;
+  result = x;
+
+  // do ten iterations
+  int i;
+  for (i = 0; i < 10; ++i) {
+    if (result <= 0) {
+      result = 0.1;
+    }
+    delta = x - (result * result);
+    result = result + 0.5 * delta / result;
+    fprintf(stdout, "Computing sqrt of %g to be %g\n", x, result);
+  }
+#endif
+  return result;
+}