to generate antlr4 java files and classes from grammar HM.g4

• $ cd /usr/local/lib

• $ sudo curl -O http://www.antlr.org/download/antlr-4.5-complete.jar

• $ export CLASSPATH=".:/usr/local/lib/antlr-4.5-complete.jar:$CLASSPATH"

• $ alias antlr4='java -jar /usr/local/lib/antlr-4.5-complete.jar'

• $ antlr4 HM.g4

• $ javac HM*.java

• Then put expression in hw8/00.in file and run TestWalk.java. see console