(lispref.info)Problems with Macros

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Common Problems Using Macros

   The basic facts of macro expansion have all been described above, but
there consequences are often counterintuitive.  This section describes
some important consequences that can lead to trouble, and rules to
follow to avoid trouble.

* Argument Evaluation
The expansion should evaluate each macro arg once.
* Surprising Local Vars
Local variable bindings in the expansion require special care.
* Eval During Expansion
Don't evaluate them; put them in the expansion.
* Repeated Expansion
Avoid depending on how many times expansion is done.

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