Build: Check for Flex and Yacc

configure.ac

@@ -5,6 +5,7 @@ AC_INIT([Harriman-Peikoff Project], [0.00.000],
 
 AC_CONFIG_SRCDIR([hcore/mind.cpp])
 AC_CONFIG_AUX_DIR([autotools-aux])
+AC_CONFIG_MACRO_DIR([m4])
 
 AM_INIT_AUTOMAKE([foreign -Wall -Werror])
 
@@ -30,14 +31,23 @@ AC_DEFINE_UNQUOTED([CONFIG_MIND_VOSCILLATOR_FREQ_MS],
     [${MIND_VOSCILLATOR_FREQ_MS}],
     [Frequency of the mind virtual oscillator in milliseconds])
 
+m4_include([m4/ac_prog_flex.m4])
+m4_include([m4/ac_prog_bison.m4])
 AC_PROG_CC
 AC_PROG_CXX
 AC_PROG_RANLIB
 AM_PROG_AR
+AC_PROG_LEX(noyywrap)
+AC_PROG_YACC
+AS_IF([test -z "${LEX}" || test -z "${YACC}"], [
+    AC_MSG_ERROR([LEX and YACC must both be available in PATH.])
+])
 
 AM_CPPFLAGS=m4_normalize(["-I\"\$(top_srcdir)/include\""])
 
 AC_SUBST([AM_CPPFLAGS])
+AC_SUBST([YACC])
+AC_SUBST([LEX])
 
 AC_CONFIG_HEADERS([include/config.h])
 AC_CONFIG_FILES([