From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Mon, 9 Dec 2019 14:49:43 +0000 (+0000)
Subject: Syntax: Use &\ for escaping; abolish \&
X-Git-Tag: subdirmk/0.3~110
X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ian/git?p=subdirmk.git;a=commitdiff_plain;h=ad2d261d58a7718898ef7146d37b9c4b8e9083ca;ds=sidebyside

Syntax: Use &\ for escaping; abolish \&

"\&" causes lots of trouble, including difficulty specifying certain
resulting strings.

Previously I proposed a scheme using &$@ but this is only useful to
provide a way to write &s.

The $-doubling regime which will come later wants a way to produce a
single literal $, so introduce that now using the same syntax.
And &\ feels quite natural to me.

Incompatible change.

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
---

diff --git a/README b/README
index 67ce6cc..d15a9f4 100644
--- a/README
+++ b/README
@@ -247,7 +247,9 @@ So pathname syntax is a subset of:
     '&' [ '^' | '~' ] [ lc | '/' | '.' | '=' ]
 
 &&		=>	&&		for convenience in shell runes
-\&		=>	&		general escaping mechanism
+
+&\&		=>	&		general escaping mechanism
+&\$		=>	$
 
 & thing thing... &
 &^ thing thing... &
@@ -285,7 +287,7 @@ So pathname syntax is a subset of:
 
 	Notably
 		STUFFSTUFF		=> STUFFSTUFF
-		\STUFF			=> STUFF
+		STUFF\STUFF		=> STUFF
 		STUFF:changequote &	=> set escape back to &
 
 &TARGETS_things
diff --git a/generate b/generate
index ba66f86..dd6df29 100755
--- a/generate
+++ b/generate
@@ -151,11 +151,11 @@ sub process_input_mk ($$$$$$$$$) {
 	    $buffering_output='';
 	}
 	for (;;) {
-	    unless (s{^(.*?)(\\)?(?=$esc)}{}) { o $_; last; }
+	    unless (s{^(.*?)$esc}{}) { o $_; last; }
 	    o $1;
-	    if ($2) { s#^$esc##; o $$esclitr; next; }
-	    s{^$esc}{} or die "$_ ?";
-	    if (s{^$esc}{}) { o "$$esclitr$$esclitr" }
+	    if (s{^\\$esc}{}) { o "$$esclitr" }
+	    elsif (s{^\\\$}{}) { o '$' }
+	    elsif (s{^$esc}{}) { o "$$esclitr$$esclitr" }
 	    elsif (s{^TARGETS(?:_([0-9a-zA-Z_]+))?(?=\W)}{}) {
 		my $t = $1 // 'all';
 		o target_varname($var_prefix, $t);