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<h4 class="subsection">12.12.11 Example of Parsing a Template String</h4>

<p>Here is an example of decoding argument types for a format string.  We
assume this is part of an interpreter which contains arguments of type
<code>NUMBER</code>, <code>CHAR</code>, <code>STRING</code> and <code>STRUCTURE</code> (and
perhaps others which are not valid here).

<pre class="smallexample">     /* <span class="roman">Test whether the </span><var>nargs</var><span class="roman"> specified objects</span>
        <span class="roman">in the vector </span><var>args</var><span class="roman"> are valid</span>
        <span class="roman">for the format string </span><var>format</var><span class="roman">:</span>
        <span class="roman">if so, return 1.</span>
        <span class="roman">If not, return 0 after printing an error message.</span>  */
     
     int
     validate_args (char *format, int nargs, OBJECT *args)
     {
       int *argtypes;
       int nwanted;
     
       /* <span class="roman">Get the information about the arguments.</span>
          <span class="roman">Each conversion specification must be at least two characters</span>
          <span class="roman">long, so there cannot be more specifications than half the</span>
          <span class="roman">length of the string.</span>  */
     
       argtypes = (int *) alloca (strlen (format) / 2 * sizeof (int));
       nwanted = parse_printf_format (string, nelts, argtypes);
     
       /* <span class="roman">Check the number of arguments.</span>  */
       if (nwanted &gt; nargs)
         {
           error ("too few arguments (at least %d required)", nwanted);
           return 0;
         }
     
       /* <span class="roman">Check the C type wanted for each argument</span>
          <span class="roman">and see if the object given is suitable.</span>  */
       for (i = 0; i &lt; nwanted; i++)
         {
           int wanted;
     
           if (argtypes[i] &amp; PA_FLAG_PTR)
             wanted = STRUCTURE;
           else
             switch (argtypes[i] &amp; ~PA_FLAG_MASK)
               {
               case PA_INT:
               case PA_FLOAT:
               case PA_DOUBLE:
                 wanted = NUMBER;
                 break;
               case PA_CHAR:
                 wanted = CHAR;
                 break;
               case PA_STRING:
                 wanted = STRING;
                 break;
               case PA_POINTER:
                 wanted = STRUCTURE;
                 break;
               }
           if (TYPE (args[i]) != wanted)
             {
               error ("type mismatch for arg number %d", i);
               return 0;
             }
         }
       return 1;
     }
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