USPExpress: getting started

You should take the following two steps when applying USPExpress to an expression:

• Parse the expression.
  Parsing results in producing an expression tree. Once the tree is built, the expression can be evaluated many times against various variable values. 
• Evaluate the expression.
  Since the expression tree is already built, evaluation of the expression is performed with maximum possible speed - no additional overhead is involved.

Below is a step-by-step guide to USPExpress usage (in C# syntax). You may also refer to the Sample projects and the Class Reference document, which are enclosed with the installation package.

USPExpress .NET Pro

1. Declare and create USP.Express.Pro.Parser object:
   

   using USP.Express.Pro; ... Parser m_cParser = new Parser();

2. Specify variables which you intend to use in your expression.
   Four variables named X1, X2, X3, X4 are specified in the example below:

   m_cParser.Variables.Add(new Variable("x1", typeof(Double))); m_cParser.Variables.Add(new Variable("x2", typeof(DateTime))); m_cParser.Variables.Add(new Variable("x3", typeof(String))); m_cParser.Variables.Add(new Variable("x4", typeof(Boolean)));

   Optionally, you may add aliases to your variables. Each variable can have one or more aliases:

   m_cParser.Variables.Item(2).Aliases.Add("OrderDate");

3. Parse the expression and obtain an expression tree: 

   ExpressionTree m_oExpressionTree = null; try { m_oExpressionTree = m_cParser.Parse("Your Expression"); } catch(Exceptions.ParseException ex) { ... } catch(Exception ex) { ... }

   ParseException is raised, if the expression is not parsed successfully.
    
4. Assign actual values to the variables that you specified on step 2: 

   object[] m_aValues = new object[4]; m_aValues[0] = 1.0; m_aValues[1] = DateTime.Now; m_aValues[2] = "test string"; m_aValues[3] = true;

5. Evaluate the expression: 

   string sResult; try { sResult = m_oExpressionTree.Evaluate(m_aValues).ToString(); } catch(Exceptions.EvaluateException ex) { MessageBox.Show(ex.Message); } catch(Exception ex) { MessageBox.Show(ex.Message); }

   EvaluateException is raised, if the expression is not evaluated successfully.

USPExpress Math Parser .NET 

1. Declare and create USPExpress.USPExpression object: 

   USPExpress.USPExpression cParser; cParser = new USPExpress.USPExpression();

2. Specify variables, which you intend to use in your expression. Three variables named X1, X2, X3 are specified in the example below: 

   string[] sVariables = new string[]{"X1", "X2", "X3"};

3. Parse the expression: 

   try { cParser.Parse(sExpression, sVariables); } catch(USPExpress.ParseException ex) { // ... }

   ParseException is raised, if the expression is not parsed successfully.
    
4. Assign actual values to the variables that you specified on step 2: 

   double[] dValues = new double[]{35, 2, 3};

   Or, if you want to evaluate an expression containing DateTime variables: 

   object[] oValues = new object[3]; oValues[0]= 35; oValues[1] = 2; oValues[2] = Convert.ToDateTime("12.12.2003");

5. Calculate: 

   double dExpValue; try { dExpValue = cParser.Evaluate(dValues); } catch(UXPExpress.EvaluateException ex) { // ... }

   Or, if you want to evaluate an expression containing DateTime variables: 

   string sExpValue; try { sExpValue = cParser.EvaluateEx(oValues); } catch(UXPExpress.EvaluateException ex) { // ... }

   EvaluateException is raised, if the expression is not evaluated successfully.