GBBopen 1.2 Reference -- defcm

defcm

defcm

name lambda-list [[declaration* | documentation]] form*=> name

[Macro]

Purpose
Define a read-time conditional compiler macro.

Package :gbbopen-tools

Module :gbbopen-tools

Arguments and values

name		A non-`nil`, non-keyword symbol that names a function or macro
lambda-list		A lambda-list
declaration		A declare expression (not evaluated)
documentation		A documentation string (not evaluated)
form		A form

Returns
The supplied name.

Description
Defcm is a read-time conditional version of Common Lisp's define-compiler-macro. As with define-compiler-macro:

The expander function is installed as a compiler macro function for name.
The &whole argument is bound to the form argument that is passed to defcm. The remaining lambda-list parameters are specified as if this form contained the function name in the car and the actual arguments in the cdr. However, if the car of the actual form is the symbol funcall, then the destructuring of the arguments is actually performed using its cddr instead.
Documentation is attached as a documentation string to name (as kind compiler-macro) and to the compiler macro function.
A compiler macro can decline to provide an expansion merely by returning the original form (which can be obtained by using &whole).

A compiler macro is not defined if the feature :disable-compiler-macros or the feature :full-safety is present when the expander function is executed on a form.

Example
Here is the compiler macro defined for ensure-list:

  > (defcm ensure-list (x)
      (with-once-only-bindings (x)
        `(if (listp ,x) ,x (list ,x))))
  ensure-list
  >

The GBBopen Project

defcm