Merge pull request #33 from bliutech/17-parser-write-a-visitor-to-tra…

…verse-the-ast

feat: Update visitor.py

parser/ast.py

@@ -2,6 +2,8 @@
     Abstract Syntax Tree (AST) for boolean expressions.
 """
 
+from visitor import Visitor
+
 
 class Var:
     """
@@ -19,6 +21,9 @@ def __init__(self, name: str):
     def __str__(self) -> str:
         return self.name
 
+    def accept(self, v: Visitor):
+        v.visitVar(self)
+
 
 class Expr:
     """
@@ -52,6 +57,9 @@ def __init__(self, first: Expr):
     def __str__(self) -> str:
         return f"& {self.first}"
 
+    def accept(self, v: Visitor):
+        v.visitAndExpr(self)
+
 
 class OrExpr(ExprPrime):
     """
@@ -69,6 +77,9 @@ def __init__(self, first: Expr):
     def __str__(self) -> str:
         return f"| {self.first}"
 
+    def accept(self, v: Visitor):
+        v.visitOrExpr(self)
+
 
 class VarExpr(Expr):
     """
@@ -93,6 +104,9 @@ def __str__(self) -> str:
 
         return f"{self.first} {self.second}"
 
+    def accept(self, v: Visitor):
+        v.visitVarExpr(self)
+
 
 class NotExpr(Expr):
     """
@@ -110,6 +124,9 @@ def __init__(self, first: Expr):
     def __str__(self) -> str:
         return f"!{self.first}"
 
+    def accept(self, v: Visitor):
+        v.visitNotExpr(self)
+
 
 class ParenExpr(Expr):
     """
@@ -126,3 +143,6 @@ def __init__(self, first: Expr):
 
     def __str__(self) -> str:
         return f"({self.first})"
+
+    def accept(self, v: Visitor):
+        v.visitParenExpr(self)

parser/visitor.py

@@ -0,0 +1,21 @@
+from parser.ast import *
+
+
+class Visitor:
+    def visitVarExpr(self, vex: VarExpr):
+        vex.first.accept(self)
+
+    def visitNotExpr(self, nex: NotExpr):
+        nex.first.accept(self)
+
+    def visitParenExpr(self, pex: ParenExpr):
+        pex.first.accept(self)
+
+    def visitAndExpr(self, aex: AndExpr):
+        aex.first.accept(self)
+
+    def visitOrExpr(self, oex: OrExpr):
+        oex.first.accept(self)
+
+    def visitVar():
+        pass