ExpressionSample - use Visitor pattern for BasicExpression.ToString

brian-dot-net · Apr 15, 2018 · 8ce466c · 8ce466c
1 parent 2f84030
commit 8ce466c
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Showing 8 changed files with 108 additions and 18 deletions.
diff --git a/projects/ExpressionSample/GWExpr.Test/GWExpr.Test.csproj b/projects/ExpressionSample/GWExpr.Test/GWExpr.Test.csproj
@@ -4,9 +4,6 @@
     <TargetFramework>netcoreapp2.0</TargetFramework>
     <IsPackable>false</IsPackable>
   </PropertyGroup>
-  <ItemGroup>
-    <None Remove="ve-BF3F.tmp" />
-  </ItemGroup>
   <ItemGroup>
     <PackageReference Include="FluentAssertions" Version="5.2.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.6.2" />

diff --git a/projects/ExpressionSample/GWExpr/BasicArray.cs b/projects/ExpressionSample/GWExpr/BasicArray.cs
@@ -30,10 +30,9 @@ public static BasicArray Str(string name, IEnumerable<BasicExpression> subs)
             return new BasicArray(BasicType.Str, name, subs);
         }
 
-        public override string ToString()
+        public override void Accept(IVisitor visit)
         {
-            var list = string.Join<BasicExpression>(", ", this.subs);
-            return this.type + "Arr(" + this.name + ", " + list + ")";
+            visit.Array(this.type, this.name, this.subs);
         }
     }
 }
diff --git a/projects/ExpressionSample/GWExpr/BasicExpression.cs b/projects/ExpressionSample/GWExpr/BasicExpression.cs
@@ -4,12 +4,92 @@
 
 namespace GWExpr
 {
+    using System.Text;
+
     public abstract class BasicExpression
     {
         protected BasicExpression()
         {
         }
 
         public static BasicExpression FromString(string input) => Expr.FromString(input);
+
+        public abstract void Accept(IVisitor visit);
+
+        public override string ToString()
+        {
+            ExpressionString str = new ExpressionString();
+            this.Accept(str);
+            return str.ToString();
+        }
+
+        private sealed class ExpressionString : IVisitor
+        {
+            private readonly StringBuilder sb;
+
+            public ExpressionString()
+            {
+                this.sb = new StringBuilder();
+            }
+
+            public void Literal(BasicType type, object o)
+            {
+                this.sb.Append(type.ToString()).Append("L(");
+
+                string s = o.ToString();
+                if (type == BasicType.Str)
+                {
+                    s = "\"" + s + "\"";
+                }
+
+                this.sb.Append(s);
+
+                this.sb.Append(")");
+            }
+
+            public void Variable(BasicType type, string name)
+            {
+                this.sb.Append(type.ToString()).Append("V(");
+
+                this.sb.Append(name);
+
+                this.sb.Append(")");
+            }
+
+            public void Array(BasicType type, string name, BasicExpression[] subs)
+            {
+                this.sb.Append(type.ToString()).Append("Arr(");
+
+                this.sb.Append(name);
+
+                foreach (BasicExpression sub in subs)
+                {
+                    this.sb.Append(", ");
+                    sub.Accept(this);
+                }
+
+                this.sb.Append(")");
+            }
+
+            public void Operator(string name, BasicExpression[] operands)
+            {
+                this.sb.Append(name).Append("(");
+
+                foreach (BasicExpression op in operands)
+                {
+                    op.Accept(this);
+                    this.sb.Append(", ");
+                }
+
+                this.sb.Remove(this.sb.Length - 2, 2);
+
+                this.sb.Append(")");
+            }
+
+            public override string ToString()
+            {
+                return this.sb.ToString();
+            }
+        }
     }
 }
diff --git a/projects/ExpressionSample/GWExpr/BasicLiteral.cs b/projects/ExpressionSample/GWExpr/BasicLiteral.cs
@@ -19,15 +19,9 @@ private BasicLiteral(BasicType type, object o)
 
         public static BasicLiteral Str(string s) => new BasicLiteral(BasicType.Str, s);
 
-        public override string ToString()
+        public override void Accept(IVisitor visit)
         {
-            string s = this.o.ToString();
-            if (this.type == BasicType.Str)
-            {
-                s = "\"" + s + "\"";
-            }
-
-            return this.type + "L(" + s + ")";
+            visit.Literal(this.type, this.o);
         }
     }
 }
diff --git a/projects/ExpressionSample/GWExpr/BasicType.cs b/projects/ExpressionSample/GWExpr/BasicType.cs
@@ -4,7 +4,7 @@
 
 namespace GWExpr
 {
-    internal enum BasicType
+    public enum BasicType
     {
         None = 0,
         Num,

diff --git a/projects/ExpressionSample/GWExpr/BasicVariable.cs b/projects/ExpressionSample/GWExpr/BasicVariable.cs
@@ -19,6 +19,9 @@ private BasicVariable(BasicType type, string name)
 
         public static BasicVariable Str(string name) => new BasicVariable(BasicType.Str, name);
 
-        public override string ToString() => this.type + "V(" + this.name + ")";
+        public override void Accept(IVisitor visit)
+        {
+            visit.Variable(this.type, this.name);
+        }
     }
 }
diff --git a/projects/ExpressionSample/GWExpr/IVisitor.cs b/projects/ExpressionSample/GWExpr/IVisitor.cs
@@ -0,0 +1,17 @@
+// <copyright file="IVisitor.cs" company="Brian Rogers">
+// Copyright (c) Brian Rogers. All rights reserved.
+// </copyright>
+
+namespace GWExpr
+{
+    public interface IVisitor
+    {
+        void Literal(BasicType type, object o);
+
+        void Variable(BasicType type, string name);
+
+        void Array(BasicType type, string name, BasicExpression[] subs);
+
+        void Operator(string name, BasicExpression[] operands);
+    }
+}
diff --git a/projects/ExpressionSample/GWExpr/OperatorExpression.cs b/projects/ExpressionSample/GWExpr/OperatorExpression.cs
@@ -30,9 +30,9 @@ public static OperatorExpression Ternary(string name, BasicExpression x, BasicEx
             return new OperatorExpression(name, new BasicExpression[] { x, y, z });
         }
 
-        public override string ToString()
+        public override void Accept(IVisitor visit)
         {
-            return this.name + "(" + string.Join<BasicExpression>(", ", this.operands) + ")";
+            visit.Operator(this.name, this.operands);
         }
     }
 }