uCalc API Version: 5.7.0-preview.1 Released: 7/30/2026

Warning

uCalc API Preview Release Notice:This preview documentation describes the intended behavior of the API. It is not fully accurate or complete.The current preview build contains incomplete features, unoptimized performance, and is subject to breaking changes.Use of the preview version in your production code is not recommended.

Clear

Method

Product: 

Transformer Library

Class: 

Tokens

Removes all token definitions from the collection, restoring it to an empty state.

Syntax

Clear()

Parameters

[None]

Return

void

This method does not return a value.

Remarks

The Clear() method erases all token definitions from a Tokens collection. This is a powerful tool for completely resetting the lexical rules of a Transformer before defining a new, custom set of tokens from scratch.

🎯 Primary Use Case: Custom Language Definition

This method is the first step in creating a parser for a completely new syntax. By default, a Transformer inherits a rich set of tokens for parsing general-purpose expressions. Clear() allows you to wipe this default set and build a new tokenizer tailored to a specific format, such as a simplified configuration language, a data format, or a Domain-Specific Language (DSL).

⚠️ Warning: The Need for a Catch-All Token

A Transformer cannot function with a completely empty token list. If no patterns match a character, the tokenizer will not advance, leading to an infinite loop or failure. After clearing the tokens, you must add at least one "catch-all" token that can match any single character to ensure the tokenizer can always make progress.

csharp
// After clearing, always add a fallback token.
t.Tokens().Clear();
t.Tokens().Add("."); // Matches any single character.

⚖️ Comparative Analysis

  • vs. Manual Remove(): While you could iterate through a Tokens collection and call Remove() on each item, Clear() is a single, optimized operation that is both faster and more direct.

  • vs. New Transformer Instance: Creating a New(uCalc::Transformer, t) also gives you a fresh start, but it begins with uCalc's default token set. Clear() is used when you want to modify the lexical rules of an existing transformer instance in-place, rather than creating a new one.

This method is the key to unlocking uCalc's full potential for dynamic language creation, allowing you to move beyond expression evaluation and into full-custom parsing.

Examples

Demonstrates the basic functionality of clearing default tokens and adding a single new one.

ID: 1021

See: Clear 
				
					using uCalcSoftware;

var uc = new uCalc();
var t = uc.NewTransformer();
t.FromTo("is", "<IS>");

Console.WriteLine("--- With Default Tokens ---");
// By default, 'is' is a whole word (token)
Console.WriteLine(t.Transform("This is a test"));

// Clear all default token definitions
t.Tokens.Clear();

// Add a new, simple token that matches any single character
t.Tokens.Add(".");

Console.WriteLine("");
Console.WriteLine("--- After Clearing and Adding '.' Token ---");
// Now, 'i' and 's' are matched as separate characters
t.FromTo("is", "<IS>"); // The rule must be redefined
Console.WriteLine(t.Transform("This is a test"));
				
			
--- With Default Tokens ---
This <IS> a test

--- After Clearing and Adding '.' Token ---
Th<IS> <IS> a test
Explore 600+ other examples
				
					#include <iostream>
#include "uCalc.h"

using namespace std;
using namespace uCalcSoftware;

int main() {
   uCalc uc;
   auto t = uc.NewTransformer();
   t.FromTo("is", "<IS>");

   cout << "--- With Default Tokens ---" << endl;
   // By default, 'is' is a whole word (token)
   cout << t.Transform("This is a test") << endl;

   // Clear all default token definitions
   t.Tokens().Clear();

   // Add a new, simple token that matches any single character
   t.Tokens().Add(".");

   cout << "" << endl;
   cout << "--- After Clearing and Adding '.' Token ---" << endl;
   // Now, 'i' and 's' are matched as separate characters
   t.FromTo("is", "<IS>"); // The rule must be redefined
   cout << t.Transform("This is a test") << endl;
}
				
			
--- With Default Tokens ---
This <IS> a test

--- After Clearing and Adding '.' Token ---
Th<IS> <IS> a test
Explore 600+ other examples
				
					Imports System
Imports uCalcSoftware
Public Module Program
   Public Sub Main()
      Dim uc As New uCalc()
      Dim t = uc.NewTransformer()
      t.FromTo("is", "<IS>")
      
      Console.WriteLine("--- With Default Tokens ---")
      '// By default, 'is' is a whole word (token)
      Console.WriteLine(t.Transform("This is a test"))
      
      '// Clear all default token definitions
      t.Tokens.Clear()
      
      '// Add a new, simple token that matches any single character
      t.Tokens.Add(".")
      
      Console.WriteLine("")
      Console.WriteLine("--- After Clearing and Adding '.' Token ---")
      '// Now, 'i' and 's' are matched as separate characters
      t.FromTo("is", "<IS>") '// The rule must be redefined
      Console.WriteLine(t.Transform("This is a test"))
   End Sub
End Module
				
			
--- With Default Tokens ---
This <IS> a test

--- After Clearing and Adding '.' Token ---
Th<IS> <IS> a test
Explore 600+ other examples
Importing a list of tokens from one transformer to another

ID: 167

See: Add(Tokens), Clear 
				
					using uCalcSoftware;

var uc = new uCalc();
var t = uc.NewTransformer();

// This creates a simpler (not very useful) set of tokens for sake of example
var MyTokens = t.Tokens;
MyTokens.Clear(); // removes the default list of tokens
MyTokens.Add("."); // Should always have a fallback token like this one
MyTokens.Add(";", TokenType.StatementSep);
MyTokens.Add("<", TokenType.Generic, ">");
MyTokens.Add("[0-9]+", TokenType.Literal);
MyTokens.Add(" +", TokenType.Whitespace);
MyTokens.Add("[a-z]+", TokenType.AlphaNumeric);

t.FromTo("{ This | That} {etc}", "[{@Self}]"); // {etc} stops at the semicolon ";" TokenType.StatementSep

Console.WriteLine(t.Transform("This is a test; That < 123.456; abc >; ABC"));
Console.WriteLine("");

var OtherTransform = new uCalc.Transformer(uc); // This is an alternative way of constructing a new transformer
OtherTransform.Tokens.Add(MyTokens); // Imports the entire token list from the other transformer
OtherTransform.Pattern("{word:1}");

Console.WriteLine(OtherTransform.Filter("This is a test; That < 123.456; abc >; ABC").Matches.Text);

				
			
[This is a test]; [That < 123.456; abc >]; ABC

This
is
a
test
;
That
<
123
.
456
;
abc
>
;
ABC
Explore 600+ other examples
				
					#include <iostream>
#include "uCalc.h"

using namespace std;
using namespace uCalcSoftware;

int main() {
   uCalc uc;
   auto t = uc.NewTransformer();

   // This creates a simpler (not very useful) set of tokens for sake of example
   auto MyTokens = t.Tokens();
   MyTokens.Clear(); // removes the default list of tokens
   MyTokens.Add("."); // Should always have a fallback token like this one
   MyTokens.Add(";", TokenType::StatementSep);
   MyTokens.Add("<", TokenType::Generic, ">");
   MyTokens.Add("[0-9]+", TokenType::Literal);
   MyTokens.Add(" +", TokenType::Whitespace);
   MyTokens.Add("[a-z]+", TokenType::AlphaNumeric);

   t.FromTo("{ This | That} {etc}", "[{@Self}]"); // {etc} stops at the semicolon ";" TokenType.StatementSep

   cout << t.Transform("This is a test; That < 123.456; abc >; ABC") << endl;
   cout << "" << endl;

   uCalc::Transformer OtherTransform(uc); // This is an alternative way of constructing a new transformer
   OtherTransform.Tokens().Add(MyTokens); // Imports the entire token list from the other transformer
   OtherTransform.Pattern("{word:1}");

   cout << OtherTransform.Filter("This is a test; That < 123.456; abc >; ABC").Matches().Text() << endl;

}
				
			
[This is a test]; [That < 123.456; abc >]; ABC

This
is
a
test
;
That
<
123
.
456
;
abc
>
;
ABC
Explore 600+ other examples
				
					Imports System
Imports uCalcSoftware
Public Module Program
   Public Sub Main()
      Dim uc As New uCalc()
      Dim t = uc.NewTransformer()
      
      '// This creates a simpler (not very useful) set of tokens for sake of example
      Dim MyTokens = t.Tokens
      MyTokens.Clear() '// removes the default list of tokens
      MyTokens.Add(".") '// Should always have a fallback token like this one
      MyTokens.Add(";", TokenType.StatementSep)
      MyTokens.Add("<", TokenType.Generic, ">")
      MyTokens.Add("[0-9]+", TokenType.Literal)
      MyTokens.Add(" +", TokenType.Whitespace)
      MyTokens.Add("[a-z]+", TokenType.AlphaNumeric)
      
      t.FromTo("{ This | That} {etc}", "[{@Self}]") '// {etc} stops at the semicolon ";" TokenType.StatementSep
      
      Console.WriteLine(t.Transform("This is a test; That < 123.456; abc >; ABC"))
      Console.WriteLine("")
      
      Dim OtherTransform As New uCalc.Transformer(uc) '// This is an alternative way of constructing a new transformer
      OtherTransform.Tokens.Add(MyTokens) '// Imports the entire token list from the other transformer
      OtherTransform.Pattern("{word:1}")
      
      Console.WriteLine(OtherTransform.Filter("This is a test; That < 123.456; abc >; ABC").Matches.Text)
      
   End Sub
End Module
				
			
[This is a test]; [That < 123.456; abc >]; ABC

This
is
a
test
;
That
<
123
.
456
;
abc
>
;
ABC
Explore 600+ other examples