GRAPHS = $(wildcard *.dot)
PDFS = $(GRAPHS:.dot=.pdf)
PNGS = $(GRAPHS:.dot=.png)

DOT_ENGINE ?= dot

.PHONY: all
all: $(PDFS) $(PNGS)

%.pdf: %.dot
	$(DOT_ENGINE) $< -Tpdf -o $@

%.png: %.dot
	$(DOT_ENGINE) $< -Tpng -o $@

.PHONY: clean
clean:
	rm -f $(PDFS) $(PNGS)