#First, we define the MACRONAMES:
SLIB = libScalar_Product.a
APP=app.x
CC = gcc
CFLAGS = -O3
LIBPATH = .  

#Then we refer to them by $(MACRONAMES):
$(APP): main.o $(SLIB) 
        $(CC) $(CFLAGS) -o $(APP) main.o -L$(LIBPATH) -lScalar_Product

main.o: main.c Scalar_Product.h
        $(CC) $(CFLAGS) -c main.c

Scalar_Product.o: Scalar_Product.c
        $(CC) $(CFLAGS) -c Scalar_Product.c

$(SLIB): Scalar_Product.o
        ar -cru $(SLIB) Scalar_Product.o
        ranlib $(SLIB)