Add Defaults For All Types

Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

Sources/Common/ProgramTypes.swift

@@ -158,6 +158,10 @@ public struct P4Struct: P4Type {
       false
     }
   }
+
+  public func def() -> any P4Value {
+    return P4StructValue(withType: self)
+  }
 }
 
 /// An instance of a P4 struct
@@ -231,6 +235,9 @@ public struct P4Boolean: P4Type {
     default: false
     }
   }
+  public func def() -> any P4Value {
+    return P4BooleanValue(withValue: false)
+  }
 }
 
 /// An instance of a P4 boolean
@@ -269,6 +276,9 @@ public struct P4Int: P4Type {
     default: false
     }
   }
+  public func def() -> any P4Value {
+    return P4IntValue(withValue: 0)
+  }
 }
 
 /// An instance of a P4 integer
@@ -309,6 +319,9 @@ public struct P4String: P4Type {
     default: false
     }
   }
+  public func def() -> any P4Value {
+    return P4StringValue(withValue: "")
+  }
 }
 /// An instance of a P4 string
 public class P4StringValue: P4Value {
@@ -358,6 +371,10 @@ public struct P4Array: P4Type {
     default: false
     }
   }
+
+  public func def() -> P4Value {
+    return P4ArrayValue(withType: self, withValue: [])
+  }
 }
 
 /// An instance of a P4 array