Sophie: sbcl-1.0.31-1mdv2010.0 i586

sbcl-1.0.31-1mdv2010.0.i586.rpm

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<h4 class="subsection">4.4.2 Errors During Macroexpansion</h4>

<p><a name="index-Macroexpansion_002c-errors-during-53"></a>
The compiler handles errors that happen during macroexpansion, turning
them into compiler errors. If you want to debug the error (to debug a
macro), you can set <code>*break-on-signals*</code> to <code>error</code>. For
example, this definition:

<pre class="lisp">     (defun foo (e l)
       (do ((current l (cdr current))
            ((atom current) nil))
           (when (eq (car current) e) (return current))))
</pre>
   <p>gives this error:

<pre class="example">     ; in: DEFUN FOO
     ;     (DO ((CURRENT L (CDR CURRENT))
     ;        ((ATOM CURRENT) NIL))
     ;       (WHEN (EQ (CAR CURRENT) E) (RETURN CURRENT)))
     ;
     ; caught ERROR:
     ;   (in macroexpansion of (DO # #))
     ;   (hint: For more precise location, try *BREAK-ON-SIGNALS*.)
     ;   DO step variable is not a symbol: (ATOM CURRENT)
</pre>
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