ENH: step 3

Tests/Tutorial/Step3/MathFunctions/CMakeLists.txt

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+add_library(MathFunctions mysqrt.cxx)
+
+install_targets (/bin MathFunctions)
+install_files (/include FILES MathFunctions.h)

Tests/Tutorial/Step3/MathFunctions/MathFunctions.h

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+double mysqrt(double x);

Tests/Tutorial/Step3/MathFunctions/mysqrt.cxx

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+#include <stdio.h>
+#include "MathFunctions.h"
+
+// a hack square root calculation using simple operations
+double mysqrt(double x)
+{
+  if (x <= 0)
+    {
+    return 0;
+    }
+  
+  double result;
+  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);
+    }
+  return result;
+}