more setup :D

.idea/vcs.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="VcsDirectoryMappings">
+    <mapping directory="$PROJECT_DIR$" vcs="Git" />
+  </component>
+</project>

README.md

@@ -0,0 +1,3 @@
+# parse with antlr
+`antlr4 -package parser.grammar  -o main/java/parser -no-listener -visitor grammar/Loop.g4`
+

grammar/Loop.g4

@@ -1 +0,0 @@
-grammar Loop;

src/grammar/Loop.g4

@@ -0,0 +1,17 @@
+grammar Loop;
+start: prog EOF;
+INT: [0-9]+ ;
+VAR: ('x'|'y'|'z') INT;
+expr: var=VAR '+' num=INT #Plus
+    | var=VAR '-' num=INT #Minus
+    ;
+asrt: var=VAR '=' ex=expr ';' #Ex
+    | var=VAR '=' var=VAR ';' #Va
+    | var=VAR '=' num=INT ';' #Num
+    ;
+prog: asrt #Asert
+    | 'LOOP' var=VAR 'DO' p=prog #Loop
+    | p1=prog p2=prog #ProgProg
+    ;
+NEWLINE : [\r\n]+ -> skip;
+LEER: ' ' -> skip;

src/main/java/compiler/grammar/Main.java

@@ -0,0 +1,22 @@
+package compiler.grammar;
+
+import org.antlr.v4.runtime.ANTLRFileStream;
+import org.antlr.v4.runtime.ANTLRInputStream;
+import org.antlr.v4.runtime.CommonTokenStream;
+import org.antlr.v4.runtime.tree.ParseTree;
+import parser.grammar.LoopLexer;
+import parser.grammar.LoopParser;
+
+import java.io.IOException;
+
+public class Main {
+    public static void main(String[] args) throws IOException {
+        ANTLRInputStream input = new ANTLRFileStream("src/main/java/compiler/grammar/test.txt");
+        LoopLexer lexer = new LoopLexer(input);
+        CommonTokenStream tokens = new CommonTokenStream(lexer);
+        LoopParser parser = new LoopParser(tokens);
+
+        ParseTree tree = parser.start();
+        new MyVisitor().visit(tree);
+    }
+}

src/main/java/compiler/grammar/MyVisitor.java

@@ -0,0 +1,14 @@
+package compiler.grammar;
+
+import parser.grammar.LoopBaseVisitor;
+import parser.grammar.LoopParser;
+
+public class MyVisitor extends LoopBaseVisitor<String> {
+    @Override
+    public String visitPlus(LoopParser.PlusContext ctx) {
+        String var = ctx.var.getText();
+        int varVal = 0; //get real value in future;
+        int num = Integer.parseInt(ctx.num.getText());
+        return Integer.valueOf(varVal + num).toString();
+    }
+}

src/main/java/compiler/grammar/test.txt

@@ -0,0 +1,4 @@
+x0 = 5;
+y0 = 10;
+LOOP y0 DO
+    x0 = x0 + 1;