X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ian/git?a=blobdiff_plain;f=README;h=20658ae2adc3087e1f24db87cababc19aaa154b9;hb=143bb5d7dfa60aa0549d934a2e9356961d97895a;hp=130a1c7fbfc085dc9d2b5b8cf65a7d1b7f9c506b;hpb=3177fb7abb48479332cce56b02b6407968fb2d27;p=subdirmk.git

diff --git a/README b/README
index 130a1c7..20658ae 100644
--- a/README
+++ b/README
@@ -340,6 +340,19 @@ STUFF $ THINGS	..	STUFF $$ THINGS
 &:endm		..	endef
 	NAME is processed for &
 
+&${..$..} =>	${eval ${call ..$$..}}
+	(matches { } pairs to find the end)
+	content is $-doubled (unless it contains $- to turn that off)
+
+	Together &:macro and &${...} provide a more reasonable macro
+	facility than raw make.  They solve the problem that make
+	expansions cannot directly generate multiple rules, variable,
+	etc.; instead, `$(eval )' must be used, but that re-expands
+	the argument, meaning that all the literal text must be
+	$-doubled.  This applies to the macro text and to the
+	arguments.  Also `$(eval $(call ...))' is an unfortunate syntax.
+	Hence &:macro and &${...}.
+
 While dollar-doubling:
 - - - - - - - - - - -