www.delorie.com/gnu/docs/autoconf/autoconf_92.html   search  
Buy the book!


[ < ] [ > ]   [ << ] [ Up ] [ >> ]         [Top] [Contents] [Index] [ ? ]

8.1.2 One Macro Call

Let's proceed on the interaction between active characters and macros with this small macro, which just returns its first argument:

define([car], [$1])

The two pairs of quotes above are not part of the arguments of define; rather, they are understood by the top level when it tries to find the arguments of define. Therefore, it is equivalent to write:

define(car, $1)

But, while it is acceptable for a `configure.ac' to avoid unnecessary quotes, it is bad practice for Autoconf macros which must both be more robust and also advocate perfect style.

At the top level, there are only two possibilities: either you quote or you don't:

car(foo, bar, baz)
[car(foo, bar, baz)]
=>car(foo, bar, baz)

Let's pay attention to the special characters:

error-->EOF in argument list

The closing parenthesis is hidden in the comment; with a hypothetical quoting, the top level understood it this way:


Proper quotation, of course, fixes the problem:


The reader will easily understand the following examples:

car(foo, bar)
car([foo, bar])
=>foo, bar
car((foo, bar))
=>(foo, bar)
car([(foo], [bar)])
car([], [])
car([[]], [[]])

With this in mind, we can explore the cases where macros invoke macros....

  webmaster     delorie software   privacy  
  Copyright 2003   by The Free Software Foundation     Updated Jun 2003