ENH: step 4

1 files changed, 39 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..0cf7db4
--- /dev/null
+++ b/Tests/Tutorial/Step4/MathFunctions/mysqrt.cxx
@@ -0,0 +1,39 @@
+#include <stdio.h>
+#include "MathFunctions.h"
+#include "TutorialConfig.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;
+}