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.

{@@...}

Product: 

Class: 

Remarks

Description: The syntax used to trigger engine-level logic dynamically at the moment a pattern match occurs, allowing the directive to use data captured during the match.

The @@ prefix is a modifier that shifts the execution of a directive from Rule Creation Time to Match Time. While a single-@ directive (like {@File}) is resolved once when the rule is defined, a double-@@ directive is resolved every single time the pattern finds a match in the source text.

Dynamic Resolution

Match-time directives are the key to building "intelligent" transformers. Because they execute during the transformation process, they have access to the local variables captured by the pattern match.

Common Match-Time Directives

  • {@@Eval:expr}: Evaluates an expression using captured data.
  • {@@File:var}: Loads a file whose name is determined by a captured variable.
  • {@@Define:var}: Dynamically sets a variable or function in the evaluator space based on the match.
  • {@@Exec:code}: Runs a procedure during the match without returning text.

Variable Syntax

When using variables captured in a pattern (e.g., {@Number:n}) within a {@@...} directive, do not use curly braces. The variable is already resident in the evaluator space for the duration of that specific match.

  • Correct: {@@Eval:n * 10}
  • Incorrect: {@@Eval:{n} * 10}

Examples

{@Eval}, {@@Eval}, and escaping special characters in a pattern

ID: 201

See: {@@...}, {@Eval}, Escapes 
				
					using uCalcSoftware;

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

t.FromTo("'['{word}']'", "{@Eval: UCase(word)}");
t.FromTo("'{'{expr}'}'", "{@@Eval: expr}");

Console.WriteLine(t.Transform("Words like [this] and [that]."));
Console.WriteLine(t.Transform("Is {5*3} bigger than {5^3}?"));
				
			
Words like THIS and THAT.
Is 15 bigger than 125?
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("'['{word}']'", "{@Eval: UCase(word)}");
   t.FromTo("'{'{expr}'}'", "{@@Eval: expr}");

   cout << t.Transform("Words like [this] and [that].") << endl;
   cout << t.Transform("Is {5*3} bigger than {5^3}?") << endl;
}
				
			
Words like THIS and THAT.
Is 15 bigger than 125?
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("'['{word}']'", "{@Eval: UCase(word)}")
      t.FromTo("'{'{expr}'}'", "{@@Eval: expr}")
      
      Console.WriteLine(t.Transform("Words like [this] and [that]."))
      Console.WriteLine(t.Transform("Is {5*3} bigger than {5^3}?"))
   End Sub
End Module
				
			
Words like THIS and THAT.
Is 15 bigger than 125?
Explore 600+ other examples
A practical, real-world example of integration: using the Transformer and Expression Parser together to create a simple template engine that replaces placeholders with evaluated data.

ID: 1359

See: {@@...}, {@Eval}, uCalc SDK 
				
					using uCalcSoftware;

var uc = new uCalc();
// Define the data context for our template
uc.DefineVariable("user = 'Alice'");
uc.DefineVariable("score = 95");

// Define the template with placeholders
var myTemplate = "User: {user}, Score: {score * 10}, Status: {IIf(score > 90, 'Excellent', 'Good')}";

var t = uc.NewTransformer();
// This single rule finds placeholders like {...}
// and uses the Expression Parser ({@@Eval}) to evaluate the content inside.
t.FromTo("'{' {expr} '}'", "{@@Eval: expr}");

Console.WriteLine(t.Transform(myTemplate));

				
			
User: Alice, Score: 950, Status: Excellent
Explore 600+ other examples
				
					#include <iostream>
#include "uCalc.h"

using namespace std;
using namespace uCalcSoftware;

int main() {
   uCalc uc;
   // Define the data context for our template
   uc.DefineVariable("user = 'Alice'");
   uc.DefineVariable("score = 95");

   // Define the template with placeholders
   auto myTemplate = "User: {user}, Score: {score * 10}, Status: {IIf(score > 90, 'Excellent', 'Good')}";

   auto t = uc.NewTransformer();
   // This single rule finds placeholders like {...}
   // and uses the Expression Parser ({@@Eval}) to evaluate the content inside.
   t.FromTo("'{' {expr} '}'", "{@@Eval: expr}");

   cout << t.Transform(myTemplate) << endl;

}
				
			
User: Alice, Score: 950, Status: Excellent
Explore 600+ other examples
				
					Imports System
Imports uCalcSoftware
Public Module Program
   Public Sub Main()
      Dim uc As New uCalc()
      '// Define the data context for our template
      uc.DefineVariable("user = 'Alice'")
      uc.DefineVariable("score = 95")
      
      '// Define the template with placeholders
      Dim myTemplate = "User: {user}, Score: {score * 10}, Status: {IIf(score > 90, 'Excellent', 'Good')}"
      
      Dim t = uc.NewTransformer()
      '// This single rule finds placeholders like {...}
      '// and uses the Expression Parser ({@@Eval}) to evaluate the content inside.
      t.FromTo("'{' {expr} '}'", "{@@Eval: expr}")
      
      Console.WriteLine(t.Transform(myTemplate))
      
   End Sub
End Module
				
			
User: Alice, Score: 950, Status: Excellent
Explore 600+ other examples