Started a cmake tutorial

Step2/MathFunctions/CMakeLists.txt

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+# TODO 14: Remove mysqrt.cxx from the list of sources
+
+# TODO 1: Add a library called MathFunctions with sources MathFunctions.cxx
+# and mysqrt.cxx
+# Hint: You will need the add_library command
+
+# TODO 7: Create a variable USE_MYMATH using option and set default to ON
+
+# TODO 8: If USE_MYMATH is ON, use target_compile_definitions to pass
+# USE_MYMATH as a precompiled definition to our source files
+
+# TODO 12: When USE_MYMATH is ON, add a library for SqrtLibrary with
+# source mysqrt.cxx
+
+# TODO 13: When USE_MYMATH is ON, link SqrtLibrary to the MathFunctions Library

Step2/MathFunctions/MathFunctions.cxx

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+#include "MathFunctions.h"
+
+// TODO 11: include cmath
+
+// TODO 10: Wrap the mysqrt include in a precompiled ifdef based on USE_MYMATH
+#include "mysqrt.h"
+
+namespace mathfunctions {
+double sqrt(double x)
+{
+  // TODO 9: If USE_MYMATH is defined, use detail::mysqrt.
+  // Otherwise, use std::sqrt.
+  return detail::mysqrt(x);
+}
+}

Step2/MathFunctions/MathFunctions.h

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+#pragma once
+
+namespace mathfunctions {
+double sqrt(double x);
+}

Step2/MathFunctions/mysqrt.cxx

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

Step2/MathFunctions/mysqrt.h

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+#pragma once
+
+namespace mathfunctions {
+namespace detail {
+double mysqrt(double x);
+}
+}