README: v2: Draft - Introduce &. and friends

[subdirmk.git] / README

diff --git a/README b/README
index bbec51884700b9776f8f9491f1b6375b0a9c1e0d..6ab45b9a3d2d80cbce38962b2fa009ed6ea3eaca 100644 (file)
--- a/README
+++ b/README
@@ -218,30 +218,44 @@ empty string).
        The assumption is that filenames are usually lowercase and
        variables usually uppercase.  Otherwise, use another syntax:
 
+&/             =>      sub/dir/                        or nothing
 &_             =>      sub_dir_                        or TOP_
-&=_            =>      sub_dir                         or TOP
+&.             =>      sub/dir                         or .
+       (This implies that `&./' works roughly like `&/', although
+       it can produce a needless `./')
 
-&/             =>      sub/dir/                        or nothing
-&=/            =>      sub/dir                         or .
+&=             =>      sub_dir                         or TOP
+^^^ rarely needed.  TBD, maybe one of
+       &._ &_. &\_ &% &$_
+       &<varnameprefix>  &[varnameprefix]
+       $(patsubst %_,&_,%)
 
 &^lc           =>      $(top_srcdir)/sub/dir/lc
 &^/            =>      $(top_srcdir)/sub/dir/
+&^.            =>      $(top_srcdir)/sub/dir
 
 &~lc           =>      $(top_srcdir)/lc
 &~/            =>      $(top_srcdir)/
+&~.            =>      $(top_srcdir)
 
 In general:
-    =  return subdir without delimiter (not allowed with `^' `~')
     ^   pathname of this subdirectory in source tree
     ~   pathname of top level of source tree
-    /  terminates the escape (needed if next is not lwsp or space)
+    /  terminates the path escape } needed if next is
+    _   terminates the var escape  } not lwsp or space)
+    .   terminates path escape giving dir name (excluding /)
+    =  terminates var escape giving only prefix part (rarely needed)
   lwsp  starts multi-word processing (see below)
 
 So pathname syntax is a subset of:
-    '&' [ '^' | '~' ] [ lc | '/' ]
+    '&' [ '^' | '~' ] [ lc | '/' | '.' | '=' ]
 
 &&             =>      &&              for convenience in shell runes
-\&             =>      &               general escaping mechanism
+&@             =>      &               general escaping mechanism
+&&@            =>      &&               @ after any number of & vanishes
+
+&$VARIABLE     $(sub/dir/VARIABLE)
+       VARIABLE is ASCII starting with a letter and matching \w+
 
 & thing thing... &
 &^ thing thing... &
@@ -261,16 +275,29 @@ So pathname syntax is a subset of:
 &:-include filename            tolerate nonexistent file
        filenames are relative to $(top_srcdir)
 
+&:section number [ident]
+       Sections will be read by make in order, first by number
+        and only then by input file (in order passed
+        to generate ie that specified in configure.ac).
+       Number is \d+; order is lexical.
+       Default section number is `5'.
+       Section numbers may not contain only `0'.
+       Section is local to &:include'd files (reset to `5'
+        on entry, restored on return).
+       Ident is [A-Za-z][A-Z0-9a-z/_-]+ and is currently unused,
+        other than appearing in output.  When used, will default
+        to source-relative input file name excluding .sd.mk.
+
 &!<lwsp>       disables & until EOL (and then disappears)
 
 &#     delete everything to end of line
        (useful if the RHS contains unrecognised & constructions)
 
-&!STUFF
+&:changequote STUFF
        changes the escape sequence from & to literally STUFF
        STUFF may be any series of of non-whitespace characters,
-       and is terminated by EOL or lwsp.  &!STUFF and the lwsp
-       are discarded.
+       and is terminated by EOL or lwsp.  The whole line is
+       discarded.
 
        After this, write STUFF instead of &, everywhere.
        The effect is global and lasts until the next setting.
@@ -278,12 +305,13 @@ So pathname syntax is a subset of:
        it back before using &:include.
 
        Notably
-               STUFFSTUFF      =>      STUFFSTUFF
-               \STUFF          =>      STUFF
-               STUFF!&         set escape back to &
+               STUFFSTUFF              => STUFFSTUFF
+               STUFF@                  => STUFF
+               STUFF:changequote &     => set escape back to &
 
 &TARGETS_things
-       Handled specially.  If mentioned, declares that this
+       Handled specially.  If mentioned at the start of a line
+       (possibly following whitespace), declares that this
        subdir ought to have a target `things'.  The rule will be
                &/things:: $(&TARGETS_things)
 
@@ -297,13 +325,39 @@ So pathname syntax is a subset of:
        which recursively implies this directory's `things'.
 
        Must be spelled exactly &TARGETS_things.  &_TARGETS_things,
-       for example, is not magic.  But mentioning &TARGETS_things in
-       a #-comment *does* work because the & filter does not care
-       about comments.
+       for example, is not magic.  To make the target exist
+       without providing any prerequisites for it, write a line
+       containing just `&TARGETS_things +='.
 
        `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
 --------------------------------