special form and macro

[alin.s]

What difference exists between a macro and a user-defined special form?

In emacs the user cannot define special forms, maybe because the macros keep
the place of special forms?

A special form should be defined as

(special (var1 ... varn) (lambda () ... ))

During application, var1 ... varn should be initialized temporary inside the
environment with the unevaluated values of the call. (name val1 ... valn).

But this is exactly the definition of a macro. Is there a difference . Is
there a computation that one can do and the other not?





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