uCalc API Version: 2.1.3-preview.2 Released: 6/16/2026

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.

Rename

Method

Product: 

Fast Math Parser

Class: 

Item

Changes the name of an existing symbol, such as a variable, function, or operator, at runtime.

Syntax

Rename(string)

Parameters

newName
string
The new name to assign to the item.

Return

Item

Returns the current Item instance to allow for method chaining.

Remarks

The Rename method provides a direct, efficient way to change the identifier of any named Item within the uCalc engine at runtime. This is a destructive operation: the original name is removed from the symbol table and is no longer valid.

This is commonly used for refactoring, adapting syntax, or wrapping existing functions with new behavior.

Impact on Dependencies

By default, uCalc expressions are statically bound when parsed. If you rename a function f to g, any existing expression that was already parsed to call f will not be automatically updated and will fail if evaluated. Renaming only affects expressions that are parsed after the rename operation has occurred.

To create dynamically-updating (reactive) expressions, you must define functions and operators with the overwrite: true flag. See DefineFunction() for more details.

⚖️ Comparative Analysis

It's important to choose the right tool for modifying symbols. Rename should be compared with Alias and text-based transformers.

  • vs. Alias()

    • Rename: A -> B (A is no longer valid).
    • Alias: A -> B (Both A and B are valid, pointing to the same underlying item).
    • Use Case: Use Rename for permanent changes or to free up a name for reuse. Use Alias to provide synonyms or for backward compatibility.

  • vs. ExpressionTransformer()

    • Rename: Operates directly on the symbol table. It is extremely fast and efficient.
    • Transformer: Performs textual search-and-replace on the raw expression string before parsing. It is much slower and can have unintended side effects if the pattern is not specific enough.
    • Use Case: Use Rename for simple name changes. Use a Transformer for complex structural changes that involve more than just a name (e.g., reordering parameters, changing operators).

Examples

Renames the Cos function (which is in Radian) to CosR and defines Cos in Degrees
				
					using uCalcSoftware;

var uc = new uCalc();
uc.DefineConstant("pi = Atan(1) * 4");

// Original Cosine behavior with Radian
Console.WriteLine(uc.EvalStr("Cos(pi)"));
Console.WriteLine(uc.EvalStr("Cos(180)"));

// Cos is renamed to CosR so that Cos can now be defined in Degree
uc.ItemOf("Cos").Rename("CosR");
uc.DefineFunction("Cos(x) = CosR(x*pi/180)");

// Now Cos is in Degree
Console.WriteLine(uc.EvalStr("Cos(pi)"));
Console.WriteLine(uc.EvalStr("Cos(180)"));

// This is the original function now named CosR
Console.WriteLine(uc.EvalStr("CosR(pi)"));
Console.WriteLine(uc.EvalStr("CosR(180)"));
// Note: Some functions may be overloaded, such as the Cos function in
// this example, which has a definition for Double and another for Complex.
// This example renames only the Double precision version.
// You can use NextOverload() and DataType() to pinpoint the one you want
				
			
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					#include <iostream>
#include "uCalc.h"

using namespace std;
using namespace uCalcSoftware;

int main() {
   uCalc uc;
   uc.DefineConstant("pi = Atan(1) * 4");

   // Original Cosine behavior with Radian
   cout << uc.EvalStr("Cos(pi)") << endl;
   cout << uc.EvalStr("Cos(180)") << endl;

   // Cos is renamed to CosR so that Cos can now be defined in Degree
   uc.ItemOf("Cos").Rename("CosR");
   uc.DefineFunction("Cos(x) = CosR(x*pi/180)");

   // Now Cos is in Degree
   cout << uc.EvalStr("Cos(pi)") << endl;
   cout << uc.EvalStr("Cos(180)") << endl;

   // This is the original function now named CosR
   cout << uc.EvalStr("CosR(pi)") << endl;
   cout << uc.EvalStr("CosR(180)") << endl;
   // Note: Some functions may be overloaded, such as the Cos function in
   // this example, which has a definition for Double and another for Complex.
   // This example renames only the Double precision version.
   // You can use NextOverload() and DataType() to pinpoint the one you want
}
				
			
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0.99849714986386
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-0.59846006905785
				
					Imports System
Imports uCalcSoftware
Public Module Program
   Public Sub Main()
      Dim uc As New uCalc()
      uc.DefineConstant("pi = Atan(1) * 4")
      
      '// Original Cosine behavior with Radian
      Console.WriteLine(uc.EvalStr("Cos(pi)"))
      Console.WriteLine(uc.EvalStr("Cos(180)"))
      
      '// Cos is renamed to CosR so that Cos can now be defined in Degree
      uc.ItemOf("Cos").Rename("CosR")
      uc.DefineFunction("Cos(x) = CosR(x*pi/180)")
      
      '// Now Cos is in Degree
      Console.WriteLine(uc.EvalStr("Cos(pi)"))
      Console.WriteLine(uc.EvalStr("Cos(180)"))
      
      '// This is the original function now named CosR
      Console.WriteLine(uc.EvalStr("CosR(pi)"))
      Console.WriteLine(uc.EvalStr("CosR(180)"))
      '// Note: Some functions may be overloaded, such as the Cos function in
      '// this example, which has a definition for Double and another for Complex.
      '// This example renames only the Double precision version.
      '// You can use NextOverload() and DataType() to pinpoint the one you want
   End Sub
End Module
				
			
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-0.59846006905785
0.99849714986386
-1
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-0.59846006905785
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