# $(if-success,<command>,<then>,<else>)
# Return <then> if <command> exits with 0, <else> otherwise.
if-success = $(shell,{ $(1); } >/dev/null 2>&1 && echo "$(2)" || echo "$(3)")

# $(success,<command>)
# Return y if <command> exits with 0, n otherwise
success = $(if-success,$(1),y,n)