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GNU macro processor

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4.5 Renaming macros

It is possible to rename an already defined macro. To do this, you need the builtin defn:

 
defn(name)

which expands to the quoted definition of name. If the argument is not a defined macro, the expansion is void.

If name is a user-defined macro, the quoted definition is simply the quoted expansion text. If, instead, name is a builtin, the expansion is a special token, which points to the builtin's internal definition. This token is only meaningful as the second argument to define (and pushdef), and is ignored in any other context.

Its normal use is best understood through an example, which shows how to rename undefine to zap:

 
define(`zap', defn(`undefine'))
=>
zap(`undefine')
=>
undefine(`zap')
=>undefine(zap)

In this way, defn can be used to copy macro definitions, and also definitions of builtin macros. Even if the original macro is removed, the other name can still be used to access the definition.

The macro defn is recognized only with parameters.


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