Index: .gitignore
===================================================================
--- .gitignore	(revision 6e7e2b36dcaa528c1778f81efe7654e171fb2197)
+++ .gitignore	(revision c3a438560523e77e6d19c2dc3cc32605a6c1e41a)
@@ -20,9 +20,9 @@
 
 # src executables, for lib and bin
-driver/cc1
-driver/cfa
+src/driver/cc1
+src/driver/cfa
 src/cfa-cpp
-libcfa/libcfa-prelude.c
+src/libcfa/libcfa-prelude.c
 
-# generated by bison and lex from cfa.y and lex.l, respectively
+# generated by bison and lex from cfa.yy and lex.ll, respectively
 src/Parser/parser.output
Index: configure
===================================================================
--- configure	(revision 6e7e2b36dcaa528c1778f81efe7654e171fb2197)
+++ configure	(revision c3a438560523e77e6d19c2dc3cc32605a6c1e41a)
@@ -4528,4 +4528,5 @@
 
 	# deprecated
+# These are often not installed and people miss seeing the "no", so stop the configure.
 for ac_prog in 'bison -y' byacc
 do
@@ -4571,4 +4572,5 @@
 test -n "$YACC" || YACC="yacc"
 
+if test "${YACC}" = "yacc" ; then echo "Error: bison required." ; exit 1 ; fi
 
 for ac_prog in flex lex
@@ -4730,4 +4732,5 @@
 
 fi
+if test "${LEX}" = "lex" ; then echo "Error: flex required." ; exit 1 ; fi
 
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether ${MAKE-make} sets \$(MAKE)" >&5
Index: configure.ac
===================================================================
--- configure.ac	(revision 6e7e2b36dcaa528c1778f81efe7654e171fb2197)
+++ configure.ac	(revision c3a438560523e77e6d19c2dc3cc32605a6c1e41a)
@@ -66,6 +66,9 @@
 AC_PROG_CC
 AM_PROG_CC_C_O	# deprecated
+# These are often not installed and people miss seeing the "no", so stop the configure.
 AC_PROG_YACC
+if test "${YACC}" = "yacc" ; then echo "Error: bison required." ; exit 1 ; fi
 AC_PROG_LEX
+if test "${LEX}" = "lex" ; then echo "Error: flex required." ; exit 1 ; fi
 AC_PROG_INSTALL
 AC_PROG_MAKE_SET