diff --git a/parser/calc/Makefile b/parser/calc/Makefile
--- a/parser/calc/Makefile
+++ b/parser/calc/Makefile
@@ -2,21 +2,21 @@
 LD=ld
 YACC=bison -y
 FLEX=flex
-CFLAGS=-Wall -O2 -ansi 
+CFLAGS=-Wall -O2 -ansi -D_XOPEN_SOURCE=500
 LDFLAGS=
 INCLUDE=include
 OBJECTS=main.o parser.o lexer.o
-TARGET=parser
+TARGET=calc
 
-.SUFFIXES: .c .yy .ll
+.SUFFIXES: .c .y .l
 
 .c.o: 
 	$(CC) -c $(CFLAGS) -I$(INCLUDE) $(CONFIG) $<
 
-.yy.c:
+.y.c:
 	$(YACC) -d $< -o $@
 
-.ll.c:
+.l.c:
 	$(FLEX) -o $@ $<
 
 all: $(TARGET)
@@ -30,6 +30,7 @@
 clean:
 	rm -f *.[oae];
 	rm -f *~;
+	rm -f parser.h
 
 distclean:
 	make clean