I Haskell School of Expression&nbsp; (p172), it says:<br><br><blockquote style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;" class="gmail_quote">A newtype declaration is just like a data declaration, except that it can only be used to defined data types with single constructor.&nbsp; The new data type is different from the analogous one created by a data declaration, in that there is no computational overhead in having the constructor.... You can think of a newtype as defining&nbsp; a &quot;new type&quot; with exactly the same structure, behaviour, and performance as the underlying type.<br>
</blockquote><br><br>What is (or where do you see) the computational overhead of the &quot;data&quot; declrations? &nbsp;&nbsp;