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copied!<p>Pretty much all the standard ways to parse a string into a scalar value of some kind in Ada will produce an exception of some kind when/if an invalid string is read. There isn't anything wrong with that. Just handle the exception.</p> <p>Even if you wrote your own string parsing to integer routines, you'd have to somehow handle the situation where the user entered an invalid string. Right?</p> <p>I guess the only "technique" involved is that you can put exception handlers on subroutines, or even on <code>declare ... begin ... end</code> blocks that you put inline in your code. This way only the code within the block is aborted. Generally I prefer to see subroutines used. So you'd get something like:</p> <pre class="lang-ada prettyprint-override"><code>function User_Integer return Integer is begin loop begin ada.integer_text_io.get(integer_variable); return integer_variable; exception when ADA.IO_EXCEPTIONS.DATA_ERROR => Ada.Text_IO.Put_Line ("Try a number from 1 to 3, Sherlock"); Print_Menu; end; end loop; end User_Integer; </code></pre> <p>Now, this being the case, for quick-and-dirty Ada menus I generally don't do numeric menus like above. Instead, make an enumerated type. That way you can print the menu options using a <code>'image</code> in a loop through the menu type, and Ada will handle the text parsing when you use <code>'value</code> or <code>Ada.Text_IO.Enumeration_IO</code>.</p> <pre class="lang-ada prettyprint-override"><code>type Menu_Selection_Option is (Eat, Drink, Sleep); package Menu_IO is new Ada.Text_IO.Enumeration_IO (Menu_Selection_Option); function User_Selection return Integer is begin loop declare Selection : Menu_Selection_Option; begin Menu_IO.Get(Selection); return Selection; exception when ADA.IO_EXCEPTIONS.DATA_ERROR => Ada.Text_IO.Put_Line ("Unrecognized option. Try again Sherlock"); Print_Menu; end; end loop; end User_Selection; </code></pre> <p>The nice thing about this is that you don't have to change your menu-printing code or your parsing code when the list of menu options changes.</p>

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