## Function: COMMON-LISP:MACROEXPAND-1
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> If form is a macro (or symbol macro), expand it once. Return two values,
> the expanded form and a T-or-NIL flag indicating whether the form was, in
> fact, a macro. ENV is the lexical environment to expand in, which defaults
> to the null environment.

### Lambda list
```cl
(sb-kernel:form &optional sb-impl::env)
```