继续翻译
A computed variable name need not consist entirely of a single variable reference. It can contain several variable references, as well as some invariant text. For example, a_dirs := dira dirb 1_dirs := dir1 dir2 a_files := filea fileb 1_files := file1 file2 ifeq "$(use_a)" "yes" a1 := a else a1 := 1 endif ifeq "$(use_dirs)" "yes" df := dirs else df := files endif dirs := $($(a1)_$(df)) will give `dirs' the same value as `a_dirs', `1_dirs', `a_files' or `1_files' depending on the settings of `use_a' and `use_dirs'. Computed variable names can also be used in substitution references: a_objects := a.o b.o c.o 1_objects := 1.o 2.o 3.o sources := $($(a1)_objects:.o=.c) defines `sources' as either `a.c b.c c.c' or `1.c 2.c 3.c', depending on the value of `a1'.
一个被计算的变量名不需要有一个单独的变量参照组成。它可以包含几个变量参照，也可以包含静态文本。例如，
a_dirs := dira dirb
1_dirs := dir1 dir2
a_files := filea fileb
1_files := file1 file2
ifeq "$(use_a)" "yes"
a1 := a
else
a1 := 1
endif
ifeq "$(use_dirs)" "yes"
df := dirs
else
df := files
endif
dirs := $($(a1)_$(df))
将要给出 `dirs' 的值为 `a_dirs', `1_dirs', `a_files' 或者
`1_files' ，这取决于 `use_a' 或者 `use_dirs'.
被计算的变量名字也可以用在替换参照中：
a_objects := a.o b.o c.o
1_objects := 1.o 2.o 3.o
sources := $($(a1)_objects:.o=.c)
定义 `sources' 为 `a.c b.c c.c' 或者 `1.c 2.c 3.c', 取决于`a1'的值。
后文待续
本文转自健哥的数据花园博客园博客，原文链接：http://www.cnblogs.com/gaojian/archive/2012/10/04/2711255.html，如需转载请自行联系原作者
