How can I simplify this Makefile to make it less repetitive?

Question

Make is one of those technologies where I go back and forth between whether or not I understand it.

This is certainly one instance where I know I must be doing something wrong, since Make was developed to make these tasks less repetitive.

all: 24.1 24.2 24.3

24.1:
    evm install emacs-24.1-bin || true
    emacs --version
    emacs --batch -L . -l ert -l test/tests.el -f ert-run-tests-batch-and-exit
24.2:
    evm install emacs-24.2-bin || true
    emacs --version
    emacs --batch -L . -l ert -l test/tests.el -f ert-run-tests-batch-and-exit
24.3:
    evm install emacs-24.3-bin || true
    emacs --version
    emacs --batch -L . -l ert -l test/tests.el -f ert-run-tests-batch-and-exit

How can I edit this Makefile to only lay out the test sequence once but be able to test against multiple versions?

Answer 1

Try this:

VERSIONS = 24.1 24.2 24.3

all :: $(VERSIONS)

$(VERSIONS) ::
    evm install emacs-$@-bin || true
    emacs --version
    emacs --batch -L . -l ert -l test/tests.el -f ert-run-tests-batch-and-exit

The :: is a special kind of rule, that puts the target as phony (and has other properties, too).