multi-wildcard pattern rules of GNU Make

Question

I want to write something like regex:

SRC:="a.dat.1 a.dat.2"    
$(SRC): %.dat.%: (\\1).rlt.(\\2)    
      dat2rlt $^ $@

so that a.dat.1 and a.dat.2 will give a.rlt.1 and a.rlt.2.

In GNU Make info page, it says "the % can be used only once".

Is there some trick to achieve this in GNU Make?

Answer 1

No, this is missing. A workaround is to add rules dynamically (with eval or include).

See e.g. this related question or this one.

Answer 2

For the limited example you gave, you can use a pattern with one %.

SRC := a.dat.1 a.dat.2
${SRC}: a.dat.%: a.rlt.%    
      dat2rlt $^ $@

1. $* in the recipe will expand to whatever the % matched.
2. Note that the "s around your original macro are definitely wrong.
3. Have a look at .SECONDEXPANSION in the manual for more complicated stuff (or over here).