Re: How to take union or intersection of two variables?

[Peng Yu]

On Thu, Dec 31, 2009 at 10:51 AM, David Boyce <address@hidden> wrote:
> On Thu, Dec 31, 2009 at 10:14 AM, Peng Yu <address@hidden> wrote:
>> On Wed, Dec 30, 2009 at 5:50 PM, Sam Ravnborg <address@hidden> wrote:
>>> union = $(sort $(A) $(B))
>>> intersection = $(filter $(A), $(B))
>>>
>>> I did not test this but I think this works.
>>
>> 'union' works, but 'intersection' should be
>>
>> intersection= $(filter $(A), $(B))
>
> Umm ... assuming there are no non-printing characters in use, this is
> absolutely identical to what Sam posted.

There are no non-printing characters in A and B. According to the
following example, ',' is required in filter, right?

$ make
Makefile:8: *** insufficient number of arguments (1) to function
`filter'.  Stop.
$ cat Makefile
.PHONY: all

A= a a b b c
B= b c d

union= $(sort $(A) $(B))
#intersection= $(filter $(A), $(B))
intersection= $(filter $(A) $(B))

intersection:
        echo $(intersection)

union:
        echo $(union)