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.

Value(double)

Method

Product: 

Fast Math Parser

Class: 

Item

Assigns a double-precision floating-point value to a uCalc variable.

Syntax

Value(double)

Parameters

value
double
The double-precision floating-point value to assign to the variable.

Return

void

This method does not return a value.

Remarks

⚙️ Overview

This method provides the primary mechanism for setting the value of a uCalc variable from the host application. It is the most common way to update variables that will be used in subsequent expression evaluations.

When a variable is created using DefineVariable, this method can be called on the returned Item object to change its stored value. This overload specifically handles double (64-bit floating-point) values.

For other data types, use their corresponding methods:

💡 Performance Note: Memory Binding

While Value() is convenient, for performance-critical applications where a variable is updated frequently inside a loop, it is more efficient to bind the uCalc variable directly to a host variable's memory address. This can be done by passing a pointer to the host variable in the variableAddress parameter of DefineVariable. This direct memory link avoids the overhead of a method call for each update.

🆚 Comparative Analysis

vs. Native Variable Assignment (C#/C++)

In a language like C#, you would assign a value directly: myVariable = 123.45;. This happens at compile time with static type checking.

uCalc's Value() method operates at runtime. This provides a powerful layer of abstraction for scripting and dynamic environments. It allows your application to control the state of a separate, sandboxed evaluation engine, which is a fundamentally different and more flexible paradigm than native variable assignment.

vs. Memory Binding

  • item.Value(123.45): Pushes a value from the host application into the uCalc engine's memory space. Involves a function call.
  • Memory Binding: The uCalc variable becomes a direct window into the host application's memory. No function call is needed to update the value; changes are reflected automatically. This is the preferred method for high-performance scenarios.

Examples

Passing arg ByExpr (delayed lazy eval) and ByHandle

ID: 14

See: (Constructor), Arg, ArgExpr, ArgItem, DefineFunction, Evaluate, Introduction, Value(double) 
				
					using uCalcSoftware;

var uc = new uCalc();

static void MySum(uCalc.Callback cb) {
   var Total = 0.0;
   var Expr = cb.ArgExpr(1);
   var Start = cb.Arg(2);
   var Finish = cb.Arg(3);
   var Variable = cb.ArgItem(4);

   for (double x = Start; x <= Finish; x++) {
      Variable.Value(x);
      Total += Expr.Evaluate();
   }
   cb.Return(Total);
}

uc.DefineVariable("x");
uc.DefineFunction("Sum(ByExpr Expr, Start, Finish, ByHandle Var)", MySum);
Console.WriteLine(uc.Eval("Sum(x ^ 2, 1, 10, x)"));

				
			
385
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					#include <iostream>
#include "uCalc.h"

using namespace std;
using namespace uCalcSoftware;

void ucalc_call MySum(uCalcBase::Callback cb) {
   auto Total = 0.0;
   auto Expr = cb.ArgExpr(1);
   auto Start = cb.Arg(2);
   auto Finish = cb.Arg(3);
   auto Variable = cb.ArgItem(4);

   for (double x = Start; x <= Finish; x++) {
      Variable.Value(x);
      Total += Expr.Evaluate();
   }
   cb.Return(Total);
}
int main() {
   uCalc uc;
   uc.DefineVariable("x");
   uc.DefineFunction("Sum(ByExpr Expr, Start, Finish, ByHandle Var)", MySum);
   cout << uc.Eval("Sum(x ^ 2, 1, 10, x)") << endl;

}
				
			
385
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					Imports System
Imports uCalcSoftware
Public Module Program
   
   Public Sub MySum(ByVal cb As uCalc.Callback)
      Dim Total = 0.0
      Dim Expr = cb.ArgExpr(1)
      Dim Start = cb.Arg(2)
      Dim Finish = cb.Arg(3)
      Dim Variable = cb.ArgItem(4)
      
      For x  As Double = Start To Finish
         Variable.Value(x)
         Total += Expr.Evaluate()
      Next
      cb.Return(Total)
   End Sub
   Public Sub Main()
      Dim uc As New uCalc()
      uc.DefineVariable("x")
      uc.DefineFunction("Sum(ByExpr Expr, Start, Finish, ByHandle Var)", AddressOf MySum)
      Console.WriteLine(uc.Eval("Sum(x ^ 2, 1, 10, x)"))
      
   End Sub
End Module
				
			
385
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Illustrates the core relationship between the uCalc engine, an Item (variable), and a compiled Expression.

ID: 31

See: Evaluate, Introduction, Memory Management, Parse, Release, Release, The uCalc Object Model - A High-Level Overview, uCalc Fast Math Parser, Value(double) 
				
					using uCalcSoftware;

var uc = new uCalc();
var VariableX = uc.DefineVariable("x");
var Expression = "x^2 * 10"; // Replace this with your expression

Console.WriteLine("--- Efficient: Parse() once, then Evaluate() in a loop ---");
var ParsedExpr = uc.Parse(Expression);
for (double x = 1; x <= 10; x++) {
   VariableX.Value(x);
   Console.WriteLine(ParsedExpr.Evaluate());
}

ParsedExpr.Release();
VariableX.Release();
				
			
--- Efficient: Parse() once, then Evaluate() in a loop ---
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					#include <iostream>
#include "uCalc.h"

using namespace std;
using namespace uCalcSoftware;

int main() {
   uCalc uc;
   auto VariableX = uc.DefineVariable("x");
   auto Expression = "x^2 * 10"; // Replace this with your expression

   cout << "--- Efficient: Parse() once, then Evaluate() in a loop ---" << endl;
   auto ParsedExpr = uc.Parse(Expression);
   for (double x = 1; x <= 10; x++) {
      VariableX.Value(x);
      cout << ParsedExpr.Evaluate() << endl;
   }

   ParsedExpr.Release();
   VariableX.Release();
}
				
			
--- Efficient: Parse() once, then Evaluate() in a loop ---
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Explore 600+ other examples
				
					Imports System
Imports uCalcSoftware
Public Module Program
   Public Sub Main()
      Dim uc As New uCalc()
      Dim VariableX = uc.DefineVariable("x")
      Dim Expression = "x^2 * 10" '// Replace this with your expression
      
      Console.WriteLine("--- Efficient: Parse() once, then Evaluate() in a loop ---")
      Dim ParsedExpr = uc.Parse(Expression)
      For x  As Double = 1 To 10
         VariableX.Value(x)
         Console.WriteLine(ParsedExpr.Evaluate())
      Next
      
      ParsedExpr.Release()
      VariableX.Release()
   End Sub
End Module
				
			
--- Efficient: Parse() once, then Evaluate() in a loop ---
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DefineVariable examples

ID: 17

See: DataType = [DataType], DefineVariable, EvaluateStr, ItemOf(string, int64, int), Name = [string], Value(), Value(double), ValueInt32(), ValueInt32(int32), ValueStr(bool), ValueStr(string) 
				
					using uCalcSoftware;

var uc = new uCalc();
var MyVar = uc.DefineVariable("MyVar");
var MyInt = uc.DefineVariable("MyInt As Int");
var MyStr = uc.DefineVariable("MyStr As String");
uc.DefineVariable("OtherStr = 'string type inferred'");
uc.DefineVariable("MyInt16 = Int16(100/3)"); // type inferred
uc.DefineVariable("MyBool = True"); // type inferred
uc.DefineVariable("MyComplex = 3 + 4*#i"); // type inferred

MyVar.Value(123);
MyInt.ValueInt32(456);
MyStr.ValueStr("This is a test");

Console.WriteLine("MyVar = " + uc.EvalStr("MyVar"));
Console.WriteLine("MyInt = " + uc.EvalStr("MyInt"));
Console.WriteLine("MyStr = " + uc.EvalStr("MyStr"));
Console.WriteLine("OtherStr = " + uc.EvalStr("OtherStr"));
Console.WriteLine("MyInt16 = " + uc.EvalStr("MyInt16"));
Console.WriteLine("MyBool = " + uc.EvalStr("MyBool"));
Console.WriteLine("MyComplex = " + uc.EvalStr("MyComplex"));
Console.WriteLine("---");
Console.WriteLine(MyVar.Value());
Console.WriteLine(MyInt.ValueInt32());
Console.WriteLine(MyStr.ValueStr());
Console.WriteLine("---");
Console.WriteLine(uc.ItemOf("MyVar").DataType.Name);
Console.WriteLine(uc.ItemOf("MyInt").DataType.Name);
Console.WriteLine(uc.ItemOf("MyStr").DataType.Name);
Console.WriteLine(uc.ItemOf("OtherStr").DataType.Name);
Console.WriteLine(uc.ItemOf("MyInt16").DataType.Name);
Console.WriteLine(uc.ItemOf("MyBool").DataType.Name);
Console.WriteLine("---");

var Expression = "x^2 * 10";
var VarX = uc.DefineVariable("x");
var ParsedExpr = uc.Parse(Expression);

Console.Write("Expression = ");
Console.WriteLine(Expression);
for (int x = 1; x <= 10; x++) {
   VarX.Value(x); // In C++ you can skip this by passing &x to DefineVariable
   Console.WriteLine("x = " + VarX.ValueStr() + "  Result = " + ParsedExpr.EvaluateStr());
}

ParsedExpr.Release();
VarX.Release();
				
			
MyVar = 123
MyInt = 456
MyStr = This is a test
OtherStr = string type inferred
MyInt16 = 33
MyBool = true
MyComplex = 3+4i
---
123
456
This is a test
---
double
int
string
string
int16
bool
---
Expression = x^2 * 10
x = 1  Result = 10
x = 2  Result = 40
x = 3  Result = 90
x = 4  Result = 160
x = 5  Result = 250
x = 6  Result = 360
x = 7  Result = 490
x = 8  Result = 640
x = 9  Result = 810
x = 10  Result = 1000
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					#include <iostream>
#include "uCalc.h"

using namespace std;
using namespace uCalcSoftware;

int main() {
   uCalc uc;
   auto MyVar = uc.DefineVariable("MyVar");
   auto MyInt = uc.DefineVariable("MyInt As Int");
   auto MyStr = uc.DefineVariable("MyStr As String");
   uc.DefineVariable("OtherStr = 'string type inferred'");
   uc.DefineVariable("MyInt16 = Int16(100/3)"); // type inferred
   uc.DefineVariable("MyBool = True"); // type inferred
   uc.DefineVariable("MyComplex = 3 + 4*#i"); // type inferred

   MyVar.Value(123);
   MyInt.ValueInt32(456);
   MyStr.ValueStr("This is a test");

   cout << "MyVar = " + uc.EvalStr("MyVar") << endl;
   cout << "MyInt = " + uc.EvalStr("MyInt") << endl;
   cout << "MyStr = " + uc.EvalStr("MyStr") << endl;
   cout << "OtherStr = " + uc.EvalStr("OtherStr") << endl;
   cout << "MyInt16 = " + uc.EvalStr("MyInt16") << endl;
   cout << "MyBool = " + uc.EvalStr("MyBool") << endl;
   cout << "MyComplex = " + uc.EvalStr("MyComplex") << endl;
   cout << "---" << endl;
   cout << MyVar.Value() << endl;
   cout << MyInt.ValueInt32() << endl;
   cout << MyStr.ValueStr() << endl;
   cout << "---" << endl;
   cout << uc.ItemOf("MyVar").DataType().Name() << endl;
   cout << uc.ItemOf("MyInt").DataType().Name() << endl;
   cout << uc.ItemOf("MyStr").DataType().Name() << endl;
   cout << uc.ItemOf("OtherStr").DataType().Name() << endl;
   cout << uc.ItemOf("MyInt16").DataType().Name() << endl;
   cout << uc.ItemOf("MyBool").DataType().Name() << endl;
   cout << "---" << endl;

   auto Expression = "x^2 * 10";
   auto VarX = uc.DefineVariable("x");
   auto ParsedExpr = uc.Parse(Expression);

   cout << "Expression = ";
   cout << Expression << endl;
   for (int x = 1; x <= 10; x++) {
      VarX.Value(x); // In C++ you can skip this by passing &x to DefineVariable
      cout << "x = " + VarX.ValueStr() + "  Result = " + ParsedExpr.EvaluateStr() << endl;
   }

   ParsedExpr.Release();
   VarX.Release();
}
				
			
MyVar = 123
MyInt = 456
MyStr = This is a test
OtherStr = string type inferred
MyInt16 = 33
MyBool = true
MyComplex = 3+4i
---
123
456
This is a test
---
double
int
string
string
int16
bool
---
Expression = x^2 * 10
x = 1  Result = 10
x = 2  Result = 40
x = 3  Result = 90
x = 4  Result = 160
x = 5  Result = 250
x = 6  Result = 360
x = 7  Result = 490
x = 8  Result = 640
x = 9  Result = 810
x = 10  Result = 1000
Explore 600+ other examples
				
					Imports System
Imports uCalcSoftware
Public Module Program
   Public Sub Main()
      Dim uc As New uCalc()
      Dim MyVar = uc.DefineVariable("MyVar")
      Dim MyInt = uc.DefineVariable("MyInt As Int")
      Dim MyStr = uc.DefineVariable("MyStr As String")
      uc.DefineVariable("OtherStr = 'string type inferred'")
      uc.DefineVariable("MyInt16 = Int16(100/3)") '// type inferred
      uc.DefineVariable("MyBool = True") '// type inferred
      uc.DefineVariable("MyComplex = 3 + 4*#i") '// type inferred
      
      MyVar.Value(123)
      MyInt.ValueInt32(456)
      MyStr.ValueStr("This is a test")
      
      Console.WriteLine("MyVar = " + uc.EvalStr("MyVar"))
      Console.WriteLine("MyInt = " + uc.EvalStr("MyInt"))
      Console.WriteLine("MyStr = " + uc.EvalStr("MyStr"))
      Console.WriteLine("OtherStr = " + uc.EvalStr("OtherStr"))
      Console.WriteLine("MyInt16 = " + uc.EvalStr("MyInt16"))
      Console.WriteLine("MyBool = " + uc.EvalStr("MyBool"))
      Console.WriteLine("MyComplex = " + uc.EvalStr("MyComplex"))
      Console.WriteLine("---")
      Console.WriteLine(MyVar.Value())
      Console.WriteLine(MyInt.ValueInt32())
      Console.WriteLine(MyStr.ValueStr())
      Console.WriteLine("---")
      Console.WriteLine(uc.ItemOf("MyVar").DataType.Name)
      Console.WriteLine(uc.ItemOf("MyInt").DataType.Name)
      Console.WriteLine(uc.ItemOf("MyStr").DataType.Name)
      Console.WriteLine(uc.ItemOf("OtherStr").DataType.Name)
      Console.WriteLine(uc.ItemOf("MyInt16").DataType.Name)
      Console.WriteLine(uc.ItemOf("MyBool").DataType.Name)
      Console.WriteLine("---")
      
      Dim Expression = "x^2 * 10"
      Dim VarX = uc.DefineVariable("x")
      Dim ParsedExpr = uc.Parse(Expression)
      
      Console.Write("Expression = ")
      Console.WriteLine(Expression)
      For x  As Integer = 1 To 10
         VarX.Value(x) '// In C++ you can skip this by passing &x to DefineVariable
         Console.WriteLine("x = " + VarX.ValueStr() + "  Result = " + ParsedExpr.EvaluateStr())
      Next
      
      ParsedExpr.Release()
      VarX.Release()
   End Sub
End Module
				
			
MyVar = 123
MyInt = 456
MyStr = This is a test
OtherStr = string type inferred
MyInt16 = 33
MyBool = true
MyComplex = 3+4i
---
123
456
This is a test
---
double
int
string
string
int16
bool
---
Expression = x^2 * 10
x = 1  Result = 10
x = 2  Result = 40
x = 3  Result = 90
x = 4  Result = 160
x = 5  Result = 250
x = 6  Result = 360
x = 7  Result = 490
x = 8  Result = 640
x = 9  Result = 810
x = 10  Result = 1000
Explore 600+ other examples
Using the parse-evaluate pattern for high-performance calculations in a loop with a changing variable w/ stopwatch.

ID: 1460

See: DefineVariable, Evaluate, Optimizing Performance in Loops, Parse, Value(double) 
				
					using uCalcSoftware;

var uc = new uCalc();
var variableX = uc.DefineVariable("x");
var userExpression = "x * 2 + 5";
var Total = 0.0;
var UpperBound = 1000000; // One million

// Parse the expression just once before the loop begins.
var parsedExpr = uc.Parse(userExpression);

var stopwatch = System.Diagnostics.Stopwatch.StartNew();
for (double x = 1; x <= UpperBound; x++) {
   variableX.Value(x);
   Total = Total + parsedExpr.Evaluate();
}
stopwatch.Stop();
//Uncomment the following line to reveal the actual speed:
//Console.WriteLine($"Elapsed Milliseconds: {stopwatch.ElapsedMilliseconds} ms");

Console.Write("Sum(1, "); Console.Write(UpperBound); Console.Write(", "); Console.Write(userExpression); Console.Write(") = "); Console.Write(Total);
				
			
Sum(1, 1000000, x * 2 + 5) = 1000006000000
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					#include <iostream>
#include "uCalc.h"

using namespace std;
using namespace uCalcSoftware;

int main() {
   uCalc uc;
   auto variableX = uc.DefineVariable("x");
   auto userExpression = "x * 2 + 5";
   auto Total = 0.0;
   auto UpperBound = 1000000; // One million

   // Parse the expression just once before the loop begins.
   auto parsedExpr = uc.Parse(userExpression);


   for (double x = 1; x <= UpperBound; x++) {
      variableX.Value(x);
      Total = Total + parsedExpr.Evaluate();
   }

   cout << "Sum(1, " << UpperBound << ", " << userExpression << ") = " << (long long)Total;
}
				
			
Sum(1, 1000000, x * 2 + 5) = 1000006000000
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					Imports System
Imports uCalcSoftware
Public Module Program
   Public Sub Main()
      Dim uc As New uCalc()
      Dim variableX = uc.DefineVariable("x")
      Dim userExpression = "x * 2 + 5"
      Dim Total = 0.0
      Dim UpperBound = 1000000 '// One million
      
      '// Parse the expression just once before the loop begins.
      Dim parsedExpr = uc.Parse(userExpression)
      
      Dim stopwatch = System.Diagnostics.Stopwatch.StartNew()
      For x  As Double = 1 To UpperBound
         variableX.Value(x)
         Total = Total + parsedExpr.Evaluate()
      Next
      stopwatch.Stop()
      '//Uncomment the following line to reveal the actual speed:
      '//Console.WriteLine($"Elapsed Milliseconds: {stopwatch.ElapsedMilliseconds} ms");
      
      Console.Write("Sum(1, ")
      Console.Write(UpperBound)
      Console.Write(", ")
      Console.Write(userExpression)
      Console.Write(") = ")
      Console.Write(Total)
   End Sub
End Module
				
			
Sum(1, 1000000, x * 2 + 5) = 1000006000000
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