Binding a uCalc variable to a host variable in your C++ code
ID: 1465
See: DefineVariable
using uCalcSoftware;
var uc = new uCalc();
// This example is mainly meant for C++ where it works with ordinary scalar variables
// See the other example where we work with a uCalc array
// 1. Use an array so the data lives on the heap as a reference type
// Boxing is used for scalar variables; a boxed copy of the scalar disconnected from the uCalc
// variable would prevent the example from working as expected.
// You technically can get around this with the C# "unsafe" directive, but it's not recommended
double[] myHostVar = new double[] { 1234.5 };
// 2. Pin the array
var myHostVarHandle = System.Runtime.InteropServices.GCHandle.Alloc(myHostVar, System.Runtime.InteropServices.GCHandleType.Pinned);
// 3. Bind the uCalc variable to the pinned memory address
uc.DefineVariable("myVar", myHostVarHandle.AddrOfPinnedObject());
Console.WriteLine(uc.Eval("myVar")); // Output: 1234.5
// Changing the uCalc variable updates the pinned array
uc.Eval("myVar = 456");
// The change is reflected in the C# array
Console.WriteLine(myHostVar[0]); // Output: 456
// Changing the C# array updates uCalc
myHostVar[0] = 9876;
Console.WriteLine(uc.Eval("myVar")); // Output: 9876
// Fast Parse & Evaluate loop
var expr = uc.Parse("myVar * 10");
for (myHostVar[0] = 1; myHostVar[0] <= 5; myHostVar[0]++) {
Console.WriteLine(expr.Evaluate());
}
// Don't forget to free the handle when you are completely done with the parser instance
myHostVarHandle.Free();
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#include <iostream>
#include "uCalc.h"
using namespace std;
using namespace uCalcSoftware;
int main() {
uCalc uc;
double myHostVar = 1234.5;
// Bind your C++ host variable to the uCalc variable like this:
uc.DefineVariable("myVar", &myHostVar);
cout << uc.Eval("myVar") << endl; // The value of the uCalc variable reflects that of the host variable
uc.Eval("myVar = 456"); // Changing the uCalc variable updates the host variable since they're linked
cout << myHostVar << endl; // The change is reflected in the C++ host variable
myHostVar = 9876; // The uCalc variable will reflect this host variable change
cout << uc.Eval("myVar") << endl;
auto expr = uc.Parse("myVar * 10");
for (myHostVar = 1; myHostVar <= 5; myHostVar++) {
cout << expr.Evaluate() << endl;
}
}
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Imports System
Imports uCalcSoftware
Public Module Program
Public Sub Main()
Dim uc As New uCalc()
'// This example is mainly meant for C++ where it works with ordinary scalar variables
'// See the other example where we work with a uCalc array
'// 1. Use an array so the data lives on the heap as a reference type
'// Boxing is used for scalar variables; a boxed copy of the scalar disconnected from the uCalc
'// variable would prevent the example from working as expected.
'// You technically can get around this with the C# "unsafe" directive, but it's not recommended
Dim myHostVar() As Double = { 1234.5 }
'// 2. Pin the array
Dim myHostVarHandle = System.Runtime.InteropServices.GCHandle.Alloc(myHostVar, System.Runtime.InteropServices.GCHandleType.Pinned)
'// 3. Bind the uCalc variable to the pinned memory address
uc.DefineVariable("myVar", myHostVarHandle.AddrOfPinnedObject())
Console.WriteLine(uc.Eval("myVar")) '// Output: 1234.5
'// Changing the uCalc variable updates the pinned array
uc.Eval("myVar = 456")
'// The change is reflected in the C# array
Console.WriteLine(myHostVar(0)) '// Output: 456
'// Changing the C# array updates uCalc
myHostVar(0) = 9876
Console.WriteLine(uc.Eval("myVar")) '// Output: 9876
'// Fast Parse & Evaluate loop
Dim expr = uc.Parse("myVar * 10")
For myHostVar(0) = 1 To 5
Console.WriteLine(expr.Evaluate())
Next
'// Don't forget to free the handle when you are completely done with the parser instance
myHostVarHandle.Free()
End Sub
End Module
1234.5
456
9876
10
20
30
40
50