# m4_split(STRING, [REGEXP])
# --------------------------
+#
# Split STRING into an m4 list of quoted elements. The elements are
# quoted with [ and ]. Beginning spaces and end spaces *are kept*.
# Use m4_strip to remove them.
#
# REGEXP specifies where to split. Default is [\t ]+.
+#
# Pay attention to the changequotes. Inner changequotes exist for
# obvious reasons (we want to insert square brackets). Outer
# changequotes are needed because otherwise the m4 parser, when it
# sees the closing bracket we add to the result, believes it is the
-# end of the body of the macro we define.
+# end of the body of the macro we define. And since the active quote
+# when `define' is called are not the ones which were used in its
+# definition, we cannot use `define' as defined above. Therefore,
+# using m4's builtin `m4_define', which is indepedent from the
+# current quotes, to define `m4_split', and then register `m4_split'
+# in libm4.
#
-# Also, notice that $1 is quoted twice, since we want the result to be
-# quoted. Then you should understand that the argument of patsubst is
-# ``STRING'' (i.e., with additional `` and '').
+# Also, notice that $1 is quoted twice, since we want the result to
+# be quoted. Then you should understand that the argument of
+# patsubst is ``STRING'' (i.e., with additional `` and '').
#
# This macro is safe on active symbols, i.e.:
# define(active, ACTIVE)
# m4_split([active active ])end
# => [active], [active], []end
-#changequote(<<, >>)
-#define(m4_split,
-#<<changequote(``, '')dnl
-#[dnl Can't use m4_default here instead of ifelse, because m4_default uses
-#dnl [ and ] as quotes.
-#patsubst(````$1'''',
-# ifelse(``$2'',, ``[ ]+'', ``$2''),
-# ``], ['')]dnl
-#changequote([, ])>>)
-#changequote([, ])
-#changequote(<<, >>)
-
-define(m4_split,
-[patsubst([[$1]],
- ifelse([$2],, [[[ ]+]], [[$2]]),
- [,])])
+
+changequote(<<, >>)
+m4_define(m4_split,
+<<changequote(``, '')dnl
+[dnl Can't use m4_default here instead of ifelse, because m4_default uses
+dnl [ and ] as quotes.
+patsubst(````$1'''',
+ ifelse(``$2'',, ``[ ]+'', ``$2''),
+ ``], ['')]dnl
+changequote([, ])>>)
+changequote([, ])
+changequote(<<, >>)
+
+m4_namespace_register(m4_split, [libm4])
+
# m4_join(STRING)
projects / thirdparty / autoconf.git / commitdiff
