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<h5 class="subsubsection">2.7.15.4 Expedient Error Messages</h5>

<p><a name="index-error-messages-367"></a>Because there are so many ways to cause an invalid deconstruction, this
message is the most common in practice and therefore the least
informative. As a matter of convenience, <code>avram</code> takes the liberty
of a slight departure from the virtual machine specification as written
hitherto, and employs the following messages when invalid
deconstructions occur respectively in the cases of recursion,
transposition, and assignment.

     <ul>
<li><code>invalid recursion</code>
<li><code>invalid transpose</code>
<li><code>invalid assignment</code>
</ul>

<p class="noindent">That is, this section contradicts and supersedes what is stated at the
end of <a href="Error-Messages.html#Error-Messages">Error Messages</a> and implied by the operator properties
<em>P14</em>, <em>P16</em>, and <em>P42</em>. It is also possible that user
applications may modify the error messages by methods described in
<a href="Computable-Error-Messages.html#Computable-Error-Messages">Computable Error Messages</a>.

   <p>Whereas these three cases constitute an expedient variation on the
semantics, there is another sense in which no possible implementation
could conform faithfully to the specification. When an evaluation can
not be carried out because of insufficient space on the host machine,
one of the following error messages may be the result.

     <ul>
<li><code>memory overflow</code>
<li><code>counter overflow</code>
</ul>

<p class="noindent">These messages are treated in the same way as those that are caused by
programming errors, and propagate to the final result written to
standard error without any specific consideration by the application
developer. The latter occurs only in connection with the built in weight
function (<a href="Weight.html#Weight">Weight</a>). Other messages listed in
<a href="Application-Programming-Errors.html#Application-Programming-Errors">Application Programming Errors</a> are also of this ilk.

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