title: Why does Stroustrup in "The C++ Programming Language 3rd Edition (online)" define the function sqrt?
body: <p>Bjarne Stroustrup, in 3rd edition (<a href="http://www.bogotobogo.com/cplusplus/files/Bjarne_Stroustrup_-_The_C++_Programming_Language_3rd_Ed.pdf">online</a>) of his book "The C++ Programming Language" chapter 2, page 23 (pdf page 34), in a snippet paradigm, defines the function <code>sqrt</code>. Why does he not just use the one already included in the standard library?</p>