[SUBDIRMK RFC 6/7] README: v2: Draft - macro assistance facility

[Ian Jackson]

Not implemented yet.  Also no S-o-b at this time!

Very much RFC.

In particular I wonder if the author of a &:macro will ever want a way
to write (say) "$(dirname $3)".  If all $ not in front of digits are
doubled in &:macro, this is impossible.  Maybe we need a literal $.
"&$@" ?  "&\$" ?  "&$$" ?  Should we provide "&\&" rather than &@ ?

Maybe "&$(" should be special ?  "&$(dirname $3)" seems quite nice
compared to "&\$(dirname $3)" or something.  Even if we do that
logically we still need provide something that expands to just the $.

Do we need something to turn on and off $-doubling ?  &$ SPC or &$$ or
something maybe.  The &:macro commit proposes two kinds of $-doubling
which means we would need multiple ways to turn it on and off.  (I'm a
bit uncomfortable with burying this $-doubling feature in a cooked
thing like &:macro.)

Maybe macro arguments are &1..&9 which expand to $1..$9, which avoids
the need for two subtly different $-doubling modes.

---
 README | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/README b/README
index e87cb80..6dd1a05 100644
--- a/README
+++ b/README
@@ -322,6 +322,32 @@ So pathname syntax is a subset of:
 	`all' is extra special: every directory has an `all'
 	target, which corresponds to &TARGETS.
 
+DRAFT - MACRO ASSISTANCE FACILITY
+---------------------------------
+
+Thanks to Mark Wooding.
+
+        &:macro NAME
+        STUFF
+        &:endm
+
+expands to
+
+        define %NAME
+        STUFF (with `$'s doubled except before a digit)
+        endef
+        NAME = $(eval $(call %NAME,$1,$2,$3,$4,$5,$6,$7,$8,$9))
+
+and
+
+        &(NAME ARG,ARG,...)
+
+expands to
+
+        $(call NAME,ARG,ARG,...)
+
+with `$'s doubled.
+
 Subdirectory and variable naming
 --------------------------------
 
-- 
2.11.0