Eval for VB/VBCE

Power up your apps with math skills!

Eval is an expression evaluator library. It evaluates almost any Visual Basic expression. You can accept expressions from the users and calculate the result with a simple call. A few examples of what you application might do:

Calculate a simple mathematical formula like "1+2+3".
Accept any formula like "x + y^2", substitute variable values and get the result.
Draw curves from user-defined formulas.
Build your own calculator.
Add expressions to your own programming language or macro system.

Eval is simple to use. Here is an example.

Formula = Textbox.Text   ' Accept input from the user, example: "1+2+3"
Result = Eval(Formula)   ' Result will be 6

No run-times required

We all know the problems with distribution of run-time files: missing files, wrong versions... Eval doesn't suffer from these problems. Eval is just a normal .bas module, or maybe two.

Just one function call is required. Evaluate(Expression). Use it to add calculation capabilities to your programs. For example, Evaluate("7+2^3") returns 15.

Supported expressions

Eval can handle all Visual Basic constant expressions:

Numbers (decimal, octal, hexa) and string literals
Numeric operators: all arithmetic, comparison and logical operators (+ - * / \ ^ Mod, etc.)
String concatenation and Like
The keywords Empty and Null
Basic single-argument functions like CInt(), Abs() or Sgn()

Eval contains an easy interface to support variables. You can also extend the module by adding more functions.

Module information

Eval comes as an ordinary source code module (Eval.bas) for Visual Basic 5.0 and 6.0. There is also a version for VBCE 6.0. It doesn't require any specific Windows version or run-time files.

VB.NET support is currently not available. Eval is written in a way that is not easily upgraded to VB.NET.

Try Eval now

Download a demo to try Eval's capabilities. The demo is a compiled program that lets you type in expressions and view the results. The demo requires VB6 run-times.

Eval is being used in several commercial applications, including Project Analyzer and VB Watch.

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