## Example code

If you put all this together, you get the source code for a small application. The application defines a parser variables ("`a`") and adds a user defined functions named "`MyFunc`". When using the parser make sure that you don't forget to catch the `Parser::exception_type` in your application. It contains detailed information helping you to find syntax errors in your formula.

    #include "muParser.h"

    // Function callback
    double MyFunction(double a_fVal)
    {
      return a_fVal*a_fVal;
    }

    // main program
    int main(int argc, char* argv[])
    {
      using namespace mu;

      try
      {
        double fVal = 1;
        Parser p;
        p.DefineVar("a", &fVal);
        p.DefineFun("MyFunc", MyFunction);
        p.SetExpr("MyFunc(a)*pi+min(10,a)");
        std::cout << p.Eval() << endl;
      }
      catch (Parser::exception_type &e)
      {
        std::cout << e.GetMsg() << endl;
      }
      return 0;
    }

## Benchmarks

Finally, I'd like to give you some benchmarks. The benchmarking was done on an Intel Pentium P-4 with 2.6 GHz, with a version compiled by using MSVC++ 7.1 (Standard edition). The diagram shows number of evaluations per seconds vs. expression length. I compared both the static lib and the dll version with two other parsers that are freely available on the net, very fast and have a similar set of features. One of them is a commercial product.

A higher curve means better performance. Expressions were created randomly. They used only `sin` and `cos` functions and contained multiple variables and constants. In order to smoothen the curves each point represents the value of a running average over 10 sample expressions.

## Release Notes

#### Rev 1.2: 14/04/2005

First of all the interface has changed so this version is not backwards compatible. After receiving a couple of questions about it, this version features support for user defined binary operators. Consequently the built in operators can now be turned off, thus you can deactivate them and write complete customized parser subclasses that only contain the functionality you want. Other new feature is the introduction of callback functions taking string arguments, implicit generation of variables and the Assignement operator.

- Functionality
  - New built in operator: `xor`; Logical xor.
  - New built in operator: Assignement operator; Defining variables in terms of other variables/constants
  - New feature: Strings as arguments for callback functions
  - New feature: User defined binary operators
  - New feature: `ParserInt` a class with a sample implementation for integer numbers.
  - New feature: Callbacks to value regognition functions.
  - Removed: all predefined postfix operators have been removed.
  - New project file: Now comes with a ready to use windows DLL.
  - New project file: Makefile for cygwin now included.
  - New example: Example3 shows usage of the DLL.
- Interface changes
  - New member function: `DefineOprt` For adding user defined binary operators.
  - New member function: `EnableBuiltInOprt(bool)` Enables/Disables built in binary operators.
  - New member function: `AddValIdent(...)` to add callbacks for custom value recognition functions.
  - Removed: `SetVar()`, `SetConst()`.
  - Renamed: Most interface functions have been renamed
  - Changed: The type for multiargument callbacks `multfun_type` has changed. It no longer takes a std::vector as input.
- Internal changes
  - new class muParserTokenReader.h encapsulates the token identification and token assignement.
  - Internal handling of function callbacks unified as a result the performance of the bytecode evaluation increased.