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.

EvaluateDbl

Method

Product: 

Fast Math Parser

Class: 

Expression

Rapidly evaluates a pre-parsed expression, optimized specifically for double-precision floating-point results.

Syntax

EvaluateDbl()

Parameters

[None]

Return

double

The double-precision floating-point result of the expression. Returns an undefined value if the expression does not yield a double.

Remarks

The EvaluateDbl method evaluates a pre-parsed expression, optimized specifically for performance-critical scenarios that return a double-precision floating-point value. It is the type-strict counterpart to the more flexible Evaluate method.

This method is a key component of uCalc's two-step evaluation model:

  1. Parse Once: Call uCalc.Parse() to convert an expression string into a compiled Expression object.
  2. Evaluate Many: Call EvaluateDbl() repeatedly on the Expression object, which is significantly faster than re-parsing the string each time with Eval().

🎯 Strict Type Enforcement

EvaluateDbl is designed for speed and requires that the parsed expression's result is a double.

  • Success: Works correctly for expressions like 3.14 * r^2.
  • Failure: Returns an undefined or incorrect value if the expression yields another numeric type (like Int32 or Boolean) or a non-numeric type (String, Complex). No conversion is attempted, and no error is raised.

Use the general-purpose Evaluate() method if your expression might return other numeric types, as it will handle the conversion to double automatically.

EvaluateDbl vs. Evaluate

FeatureEvaluateDbl()Evaluate()
Performance🟢 Highest. Optimized for direct double evaluation.🟡 High. Slightly slower due to type-checking and potential conversion logic.
Type Safety🔴 Strict. Only works for expressions returning double.🟢 Flexible. Handles any numeric type by converting it to double.
Use CaseIdeal for high-speed loops in scientific or financial calculations where the return type is known to be double.General-purpose numeric evaluation where flexibility is more important than maximum performance.

💡 Comparative Analysis: Why Use a Two-Step Process?

In many programming environments, evaluating a string expression is a single, monolithic operation. uCalc separates parsing from evaluation, which mirrors how compilers work and offers significant performance advantages.

  • vs. eval() in Scripting Languages: Functions like JavaScript's eval() re-parse the string on every call, making them inefficient for loops.
  • vs. C# DataTable.Compute: This common .NET workaround is notoriously slow because it involves significant overhead for each calculation.
  • vs. Compiled Code: The Parse step is analogous to a just-in-time (JIT) compilation. Once the Expression object is created, calls to EvaluateDbl are nearly as fast as calling a native, compiled function, but with the full dynamic flexibility of a runtime engine.

This model allows uCalc to achieve performance levels suitable for real-time simulations and data processing tasks that would be too slow for traditional script evaluators.

Examples

Evaluate() auto-conversion
				
					using uCalcSoftware;

var uc = new uCalc();
// The int return value type in MyExprB is converted to
// Double with .Evaluate(), but not with .EvaluateDbl()
var MyExprA = uc.Parse("3.2 + 5.2");
var MyExprB = uc.Parse("int(3.2 + 5.2)");

Console.WriteLine(MyExprA.Evaluate());
Console.WriteLine(MyExprA.EvaluateDbl() == 8.4);
Console.WriteLine(MyExprB.Evaluate());
Console.WriteLine(MyExprB.EvaluateDbl() == 8);
				
			
8.4
True
8
False
				
					#include <iostream>
#include "uCalc.h"

using namespace std;
using namespace uCalcSoftware;

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

int main() {
   uCalc uc;
   // The int return value type in MyExprB is converted to
   // Double with .Evaluate(), but not with .EvaluateDbl()
   auto MyExprA = uc.Parse("3.2 + 5.2");
   auto MyExprB = uc.Parse("int(3.2 + 5.2)");

   cout << MyExprA.Evaluate() << endl;
   cout << tf(MyExprA.EvaluateDbl() == 8.4) << endl;
   cout << MyExprB.Evaluate() << endl;
   cout << tf(MyExprB.EvaluateDbl() == 8) << endl;
}
				
			
8.4
True
8
False
				
					Imports System
Imports uCalcSoftware
Public Module Program
   Public Sub Main()
      Dim uc As New uCalc()
      '// The int return value type in MyExprB is converted to
      '// Double with .Evaluate(), but not with .EvaluateDbl()
      Dim MyExprA = uc.Parse("3.2 + 5.2")
      Dim MyExprB = uc.Parse("int(3.2 + 5.2)")
      
      Console.WriteLine(MyExprA.Evaluate())
      Console.WriteLine(MyExprA.EvaluateDbl() = 8.4)
      Console.WriteLine(MyExprB.Evaluate())
      Console.WriteLine(MyExprB.EvaluateDbl() = 8)
   End Sub
End Module
				
			
8.4
True
8
False
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