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This page demonstrates how to quickly get started in creating and evaluating expressions. You'll need to add a reference to Ciloci.Flee.dll and import the Ciloci.Flee namespace to be able to compile the code.

// Define the context of our expression ExpressionContext context = new ExpressionContext(); // Allow the expression to use all static public methods of System.Math context.Imports.AddType(typeof(Math)); // Define an int variable context.Variables["a"] = 100; // Create a dynamic expression that evaluates to an Object IDynamicExpression eDynamic = context.CompileDynamic("sqrt(a) + pi"); // Create a generic expression that evaluates to a double IGenericExpression<double> eGeneric = context.CompileGeneric<double>("sqrt(a) + pi"); // Evaluate the expressions double result = (double)eDynamic.Evaluate(); result = eGeneric.Evaluate(); // Update the value of our variable context.Variables["a"] = 144; // Evaluate again to get the updated result result = eGeneric.Evaluate();

The ExpressionContext holds all the information required for an expression (besides the expression text). We use its Imports property to make all the static members of the System.Math class available to the expression and the Variables property to dynamically define some variables. With the context defined, we compile the expression text to create a dynamic expression (evaluates to Object) or a generic expression (type-safe and fast) and finally call the Evaluate method on either expression to get its result.

Expressions can fail to compile if, for example, the syntax of the text is invalid. An ExpressionCompileExpression will be thrown whenever an expression cannot be compiled.

try { ExpressionContext context = new ExpressionContext(); IDynamicExpression e = context.CompileDynamic("100 +* 200"); } catch (ExpressionCompileException ex) { // Handle expression compile error if (ex.Reason == CompileExceptionReason.SyntaxError) Console.WriteLine("Check your expression syntax"); }

Last edited Nov 9, 2008 at 10:05 PM by ECiloci, version 22

@bhrnjica

For that you need custom functions and a bit of black magic:

public static class CustomFunctions{

public static double isZero(double x) {

return (x == 0.0) ? 1.0 : 0.0;

}

}

class Program {

static void Main(string[] args) {

ExpressionContext context = new ExpressionContext();

IDynamicExpression eDynamic;

double r1, r2;

context.Imports.AddType(typeof(CustomFunctions));

context.Variables.Add("a1", 0.0);

context.Variables.Add("a2", 0.0);

eDynamic = context.CompileDynamic("isZero(a2)*1.0 + (1.0-isZero(a2))*(a1/(a2+isZero(a2)))");

context.Variables["a1"] = 1.0;

// a2 zero

context.Variables["a2"] = 0.0;

r1 = (double)eDynamic.Evaluate();

// a2 not zero

context.Variables["a2"] = 10.0;

r2 = (double)eDynamic.Evaluate();

Console.WriteLine("{0}\n{1}", r1, r2);

}

}

For that you need custom functions and a bit of black magic:

public static class CustomFunctions{

public static double isZero(double x) {

return (x == 0.0) ? 1.0 : 0.0;

}

}

class Program {

static void Main(string[] args) {

ExpressionContext context = new ExpressionContext();

IDynamicExpression eDynamic;

double r1, r2;

context.Imports.AddType(typeof

context.Variables.Add("a1", 0.0);

context.Variables.Add("a2", 0.0);

eDynamic = context.CompileDynamic("isZero

context.Variables["a1"] = 1.0;

// a2 zero

context.Variables["a2"] = 0.0;

r1 = (double)eDynamic.Evaluate();

// a2 not zero

context.Variables["a2"] = 10.0;

r2 = (double)eDynamic.Evaluate();

Console.WriteLine("{0}\n{1}", r1, r2);

}

}

Hi, your lib is great, but i have one quest,

I need division with check for arg2: if(a2==0, 1,a1/a2)

how can i achieve this

I need division with check for arg2: if(a2==0, 1,a1/a2)

how can i achieve this