CVSROOT: /sources/m4
Module name: m4
Changes by: Eric Blake <ericb> 06/10/14 14:16:23
Index: doc/m4.texinfo
===================================================================
RCS file: /sources/m4/m4/doc/m4.texinfo,v
retrieving revision 1.64
retrieving revision 1.65
diff -u -b -r1.64 -r1.65
--- doc/m4.texinfo 13 Oct 2006 16:46:47 -0000 1.64
+++ doc/m4.texinfo 14 Oct 2006 14:16:23 -0000 1.65
@@ -268,6 +268,7 @@
Correct version of some examples
+* Improved exch:: Solution for @code{exch}
* Improved foreach:: Solution for @code{foreach}
* Improved cleardivert:: Solution for @code{cleardivert}
* Improved fatal_error:: Solution for @code{fatal_error}
@@ -5706,11 +5707,30 @@
presented here.
@menu
+* Improved exch:: Solution for @code{exch}
* Improved foreach:: Solution for @code{foreach}
* Improved cleardivert:: Solution for @code{cleardivert}
* Improved fatal_error:: Solution for @code{fatal_error}
@end menu
[EMAIL PROTECTED] Improved exch
[EMAIL PROTECTED] Solution for @code{exch}
+
+The @code{exch} macro (@pxref{Arguments}) as presented requires clients
+to double quote their arguments. A nicer definition, which lets
+clients follow the rule of thumb of one level of quoting per level of
+parentheses, involves adding quotes in the definition of @code{exch}, as
+follows:
+
[EMAIL PROTECTED]
+define(`exch', ``$2', `$1'')
[EMAIL PROTECTED]
+define(exch(`expansion text', `macro'))
[EMAIL PROTECTED]
+macro
[EMAIL PROTECTED] text
[EMAIL PROTECTED] example
+
@node Improved foreach
@section Solution for @code{foreach}
@@ -5795,20 +5815,36 @@
@section Solution for @code{cleardivert}
The @code{cleardivert} macro (@pxref{Cleardiv}) cannot, as it stands, be
-called without arguments to clear all pending diversions. A macro that
-achieves that as well is:
+called without arguments to clear all pending diversions. That is
+because using undivert with an empty string for an argument is different
+than using it with no arguments at all. Compare the earlier definition
+with one that takes the number of arguments into account:
[EMAIL PROTECTED] ignore
@example
define(`cleardivert',
-`pushdef(`_num', divnum)divert(-1)ifelse($#, 0,
+ `pushdef(`_n', divnum)divert(`-1')undivert($@@)divert(_n)popdef(`_n')')
[EMAIL PROTECTED]
+divert(`1')one
+divert
[EMAIL PROTECTED]
+cleardivert
[EMAIL PROTECTED]
+undivert
[EMAIL PROTECTED]
[EMAIL PROTECTED]
+define(`cleardivert',
+ `pushdef(`_num', divnum)divert(`-1')ifelse(`$#', `0',
`undivert`'', `undivert($@@)')divert(_num)popdef(`_num')')
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+divert(`2')two
+divert
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+cleardivert
[EMAIL PROTECTED]
+undivert
[EMAIL PROTECTED]
@end example
[EMAIL PROTECTED]
-If called without arguments, it will call undivert without argument,
-otherwise they will be passed to undivert().
-
@node Improved fatal_error
@section Solution for @code{fatal_error}
@@ -5823,7 +5859,7 @@
@comment status: 1
@example
define(`fatal_error',
- `errprint(ifdef(`__program', `__program__', ``m4'')'dnl
+ `errprint(ifdef(`__program__', `__program__', ``m4'')'dnl
`:ifelse(__line__, `0', `',
`__file__:__line__:')` fatal error: $*
')m4exit(`1')')
