add Decaf.g4

src/main/antlr/Decaf.g4

@@ -0,0 +1,69 @@
+grammar Decaf;
+
+program : (class)+;
+
+class : PUBLIC? 'class' id '{' (var | meth)* '}';
+
+var : type id ';' | type id '=' expr';';
+returntype : type | VOID;
+type : INT | BOOL;
+
+meth : PUBLIC? 'static'? returntype id '(' params? ')' block;
+params : param (',' param)*;
+param : type id;
+
+block : '{' (var | stmt)* '}';
+
+stmt : 'if' '(' expr ')' block ('else' block)?  #If
+    | 'for' '(' expr? ';' expr? ';' expr? ')' block  #For
+    | 'while' '(' expr ')' block                #While
+    | 'do' block 'while' '(' expr ')'           #DoWhile
+    | 'return' expr ';'                         #Return
+    | 'return' ';'                              #ReturnVoid
+    | 'break' ';'                               #Break
+    | 'continue' ';'                            #Continue
+    | stmtexpr                                  #StatementExpressionstmt
+    ;
+
+stmtexpr : id '=' expr ';'                      #Assign
+    | methCall ';'                              #MethodCall
+    | NEW type '(' params* ')'                  #New
+    ;
+
+expr : expr binaryOp expr   #BinaryOperation
+    | literal               #Constant
+    | '(' expr ')'          #Expression
+    | methCall              #MethodCallExpression
+    | id                    #Identifier
+    | stmtexpr              #StatementExpressionexpr
+;
+
+binaryOp : ADD | SUB | MUL;
+
+
+methCall : id '(' args? ')';
+args : expr (',' expr)*;
+
+literal : NUMBER | boolean;
+
+boolean : 'true' | 'false' ;
+
+id : IDENTIFIER;
+
+
+PUBLIC : 'public';
+NEW : 'new';
+
+SUB : '-';
+ADD : '+';
+MUL : '*';
+
+INT : 'int';
+BOOL : 'bool';
+VOID : 'void';
+
+IDENTIFIER : [a-zA-Z]+;
+NUMBER : [0-9]+;
+WS : [ \t\r\n] -> skip;
+
+