uCalc API Version: 2.1.3-preview.2 Released: 6/17/2026

Warning

uCalc API Preview Release Notice:The documentation describes the intended behavior of the API. The current preview build contains incomplete features, unoptimized performance, and is subject to breaking changes.

ParentTransformer = [Transformer]

Property

Product: 

Transformer Library

Class: 

Rule

Retrieves the parent Transformer instance that owns this rule, providing a navigational link back to the rule's execution context.

Remarks

🧭 Navigating the Hierarchy: ParentTransformer

Every Rule object exists within the context of a parent Transformer that owns it. The ParentTransformer property provides the crucial link back to this owner, allowing you to navigate "up" the object hierarchy from a specific rule to its container.

This is essential for introspection and for writing context-aware transformation logic, especially when dealing with nested transformers.

🎯 Primary Use Cases

  1. Contextual Introspection: When you retrieve a Rule from a Match object, you can use ParentTransformer to access the state of the Transformer that found the match. This allows you to read its Description, check its other rules, or inspect its token set.

  2. Distinguishing Local vs. Global Context: When using a LocalTransformer for nested parsing, this property is the primary way to determine which level of the hierarchy a rule belongs to. A rule inside a LocalTransformer will have that LocalTransformer as its parent, not the main, top-level Transformer.

💡 Why uCalc? (Comparative Analysis)

This parent-child relationship is a common design pattern for creating navigable object trees.

  • vs. DOM (Document Object Model): The relationship between a Rule and its ParentTransformer is analogous to an HTML element and its parentElement in the DOM. It provides a structured, predictable way to traverse the hierarchy of your parsing logic. Just as you might walk up the DOM tree from a specific <div> to find its container, you can walk up from a Rule to its owning Transformer.

  • vs. Ad-Hoc Rule Management: Without this built-in link, you would need to manually track which Transformer owns which Rule, likely using external dictionaries or wrapper classes. This is complex and error-prone. By making ParentTransformer a first-class property, uCalc provides a clean, reliable, and integrated solution for managing the relationship between rules and their execution context.

Examples

Verifies the direct parent-child relationship between a Transformer and its Rule.
				
					using uCalcSoftware;

var uc = new uCalc();
var t = new uCalc.Transformer();
var myRule = t.FromTo("A", "B");

// Get the parent from the rule
var parent = myRule.ParentTransformer;

// Check if the parent is the original transformer using its unique memory index
Console.WriteLine(parent.MemoryIndex == t.MemoryIndex);
				
			
True
				
					#include <iostream>
#include "uCalc.h"

using namespace std;
using namespace uCalcSoftware;

#define tf(IsTrue) ((IsTrue) ? "True" : "False")

int main() {
   uCalc uc;
   uCalc::Transformer t;
   auto myRule = t.FromTo("A", "B");

   // Get the parent from the rule
   auto parent = myRule.ParentTransformer();

   // Check if the parent is the original transformer using its unique memory index
   cout << tf(parent.MemoryIndex() == t.MemoryIndex()) << endl;
}
				
			
True
				
					Imports System
Imports uCalcSoftware
Public Module Program
   Public Sub Main()
      Dim uc As New uCalc()
      Dim t As New uCalc.Transformer()
      Dim myRule = t.FromTo("A", "B")
      
      '// Get the parent from the rule
      Dim parent = myRule.ParentTransformer
      
      '// Check if the parent is the original transformer using its unique memory index
      Console.WriteLine(parent.MemoryIndex = t.MemoryIndex)
   End Sub
End Module
				
			
True
Iterates through matches, retrieves the rule for each, and uses ParentTransformer to get the transformer's description for context.
				
					using uCalcSoftware;

var uc = new uCalc();
var t = new uCalc.Transformer();
t.Description = "My Main Transformer";
t.Text = "apple banana apple";

var appleRule = t.FromTo("apple", "APPLE");
var bananaRule = t.FromTo("banana", "BANANA");

t.Find();

foreach(var match in t.Matches) {
   var rule = match.Rule;
   var parent = rule.ParentTransformer;
   Console.WriteLine($"Match '{match.Text}' found by rule '{rule.Name}' in transformer '{parent.Description}'");
}
				
			
Match 'apple' found by rule 'apple' in transformer 'My Main Transformer'
Match 'banana' found by rule 'banana' in transformer 'My Main Transformer'
Match 'apple' found by rule 'apple' in transformer 'My Main Transformer'
				
					#include <iostream>
#include "uCalc.h"

using namespace std;
using namespace uCalcSoftware;

int main() {
   uCalc uc;
   uCalc::Transformer t;
   t.Description("My Main Transformer");
   t.Text("apple banana apple");

   auto appleRule = t.FromTo("apple", "APPLE");
   auto bananaRule = t.FromTo("banana", "BANANA");

   t.Find();

   for(auto match : t.Matches()) {
      auto rule = match.Rule();
      auto parent = rule.ParentTransformer();
      cout << "Match '" << match.Text() << "' found by rule '" << rule.Name() << "' in transformer '" << parent.Description() << "'" << endl;
   }
}
				
			
Match 'apple' found by rule 'apple' in transformer 'My Main Transformer'
Match 'banana' found by rule 'banana' in transformer 'My Main Transformer'
Match 'apple' found by rule 'apple' in transformer 'My Main Transformer'
				
					Imports System
Imports uCalcSoftware
Public Module Program
   Public Sub Main()
      Dim uc As New uCalc()
      Dim t As New uCalc.Transformer()
      t.Description = "My Main Transformer"
      t.Text = "apple banana apple"
      
      Dim appleRule = t.FromTo("apple", "APPLE")
      Dim bananaRule = t.FromTo("banana", "BANANA")
      
      t.Find()
      
      For Each match In t.Matches
         Dim rule = match.Rule
         Dim parent = rule.ParentTransformer
         Console.WriteLine($"Match '{match.Text}' found by rule '{rule.Name}' in transformer '{parent.Description}'")
      Next
   End Sub
End Module
				
			
Match 'apple' found by rule 'apple' in transformer 'My Main Transformer'
Match 'banana' found by rule 'banana' in transformer 'My Main Transformer'
Match 'apple' found by rule 'apple' in transformer 'My Main Transformer'
Internal Test: Verifies that the correct parent is returned when using a nested LocalTransformer, confirming hierarchical integrity.
				
					using uCalcSoftware;

var uc = new uCalc();
var main_t = new uCalc.Transformer();
main_t.Description = "Main Transformer";

// Create an outer rule in the main transformer
var outerRule = main_t.Pattern("OUTER({body})");

// Get a local transformer for the outer rule
var local_t = outerRule.LocalTransformer;
local_t.Description = "Local Transformer";

// Create an inner rule inside the local transformer
var innerRule = local_t.FromTo("INNER", "inner_match");

// Verify the parent of the outer rule is the main transformer
Console.WriteLine($"Outer rule's parent: {outerRule.ParentTransformer.Description}");

// Verify the parent of the inner rule is the local transformer
Console.WriteLine($"Inner rule's parent: {innerRule.ParentTransformer.Description}");
				
			
Outer rule's parent: Main Transformer
Inner rule's parent: Local Transformer
				
					#include <iostream>
#include "uCalc.h"

using namespace std;
using namespace uCalcSoftware;

int main() {
   uCalc uc;
   uCalc::Transformer main_t;
   main_t.Description("Main Transformer");

   // Create an outer rule in the main transformer
   auto outerRule = main_t.Pattern("OUTER({body})");

   // Get a local transformer for the outer rule
   auto local_t = outerRule.LocalTransformer();
   local_t.Description("Local Transformer");

   // Create an inner rule inside the local transformer
   auto innerRule = local_t.FromTo("INNER", "inner_match");

   // Verify the parent of the outer rule is the main transformer
   cout << "Outer rule's parent: " << outerRule.ParentTransformer().Description() << endl;

   // Verify the parent of the inner rule is the local transformer
   cout << "Inner rule's parent: " << innerRule.ParentTransformer().Description() << endl;
}
				
			
Outer rule's parent: Main Transformer
Inner rule's parent: Local Transformer
				
					Imports System
Imports uCalcSoftware
Public Module Program
   Public Sub Main()
      Dim uc As New uCalc()
      Dim main_t As New uCalc.Transformer()
      main_t.Description = "Main Transformer"
      
      '// Create an outer rule in the main transformer
      Dim outerRule = main_t.Pattern("OUTER({body})")
      
      '// Get a local transformer for the outer rule
      Dim local_t = outerRule.LocalTransformer
      local_t.Description = "Local Transformer"
      
      '// Create an inner rule inside the local transformer
      Dim innerRule = local_t.FromTo("INNER", "inner_match")
      
      '// Verify the parent of the outer rule is the main transformer
      Console.WriteLine($"Outer rule's parent: {outerRule.ParentTransformer.Description}")
      
      '// Verify the parent of the inner rule is the local transformer
      Console.WriteLine($"Inner rule's parent: {innerRule.ParentTransformer.Description}")
   End Sub
End Module
				
			
Outer rule's parent: Main Transformer
Inner rule's parent: Local Transformer
ParentTransformer
				
					using uCalcSoftware;

var uc = new uCalc();
var Txt = "Test a b c. x y z";

var FirstTransform = uc.NewTransformer().SetText(Txt).SetDescription("First Transformer");
var aaa = FirstTransform.FromTo("Test {etc}.", "[{etc}]");

var SecondTransform = uc.NewTransformer().SetDescription("Second Transformer");
var bbb = SecondTransform.FromTo("Test {etc}.", "({etc})");

Console.WriteLine(aaa.ParentTransformer.Description);
Console.WriteLine(FirstTransform.Transform().Text);
Console.WriteLine("");

Console.WriteLine(SecondTransform.Description);
Console.WriteLine(bbb.ParentTransformer.Transform(Txt).Text);
				
			
First Transformer
[a b c] x y z

Second Transformer
(a b c) x y z
				
					#include <iostream>
#include "uCalc.h"

using namespace std;
using namespace uCalcSoftware;

int main() {
   uCalc uc;
   auto Txt = "Test a b c. x y z";

   auto FirstTransform = uc.NewTransformer().SetText(Txt).SetDescription("First Transformer");
   auto aaa = FirstTransform.FromTo("Test {etc}.", "[{etc}]");

   auto SecondTransform = uc.NewTransformer().SetDescription("Second Transformer");
   auto bbb = SecondTransform.FromTo("Test {etc}.", "({etc})");

   cout << aaa.ParentTransformer().Description() << endl;
   cout << FirstTransform.Transform().Text() << endl;
   cout << "" << endl;

   cout << SecondTransform.Description() << endl;
   cout << bbb.ParentTransformer().Transform(Txt).Text() << endl;
}
				
			
First Transformer
[a b c] x y z

Second Transformer
(a b c) x y z
				
					Imports System
Imports uCalcSoftware
Public Module Program
   Public Sub Main()
      Dim uc As New uCalc()
      Dim Txt = "Test a b c. x y z"
      
      Dim FirstTransform = uc.NewTransformer().SetText(Txt).SetDescription("First Transformer")
      Dim aaa = FirstTransform.FromTo("Test {etc}.", "[{etc}]")
      
      Dim SecondTransform = uc.NewTransformer().SetDescription("Second Transformer")
      Dim bbb = SecondTransform.FromTo("Test {etc}.", "({etc})")
      
      Console.WriteLine(aaa.ParentTransformer.Description)
      Console.WriteLine(FirstTransform.Transform().Text)
      Console.WriteLine("")
      
      Console.WriteLine(SecondTransform.Description)
      Console.WriteLine(bbb.ParentTransformer.Transform(Txt).Text)
   End Sub
End Module
				
			
First Transformer
[a b c] x y z

Second Transformer
(a b c) x y z
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