Help/guide/tutorial: Adopt tutorial code

1 files changed, 41 insertions, 0 deletions

diff --git a/Help/guide/tutorial/Step9/MathFunctions/mysqrt.cxx b/Help/guide/tutorial/Step9/MathFunctions/mysqrt.cxx
new file mode 100644
index 0000000..8b82141
--- /dev/null
+++ b/Help/guide/tutorial/Step9/MathFunctions/mysqrt.cxx
@@ -0,0 +1,41 @@
+#include "MathFunctions.h"
+#include <iostream>
+
+// include the generated table
+#include "Table.h"
+
+#include <cmath>
+
+// a hack square root calculation using simple operations
+double mysqrt(double x)
+{
+  if (x <= 0) {
+    return 0;
+  }
+
+  // if we have both log and exp then use them
+#if defined(HAVE_LOG) && defined(HAVE_EXP)
+  double result = exp(log(x) * 0.5);
+  std::cout << "Computing sqrt of " << x << " to be " << result << " using log"
+            << std::endl;
+#else
+  // use the table to help find an initial value
+  double result = x;
+  if (x >= 1 && x < 10) {
+    result = sqrtTable[static_cast<int>(x)];
+  }
+
+  // if we have both log and exp then use them
+
+  // do ten iterations
+  for (int i = 0; i < 10; ++i) {
+    if (result <= 0) {
+      result = 0.1;
+    }
+    double delta = x - (result * result);
+    result = result + 0.5 * delta / result;
+    std::cout << "Computing sqrt of " << x << " to be " << result << std::endl;
+  }
+#endif
+  return result;
+}