LIBEXPRESSION - library that provides a mechanism for solving math expressions

Overview

Libexpression library provides a mechanism for solving valid math and logical expressions for other programs. It is intended to allow programmers to integrate a user-frielndly calculators/expressions into their programs.

Libexpression is based on RPN algorithm with several powerful modifications, such as trinary operators, variable arguments functions and user defined callbacks.

Almost all functions in the library are thread-safe. All non thread-safe functions have their thread-safe analogs. Please, refer to the example below to see how to use this library.

Requirements

This library does not require any extra packages.

Installation Instructions

The simplest way to compile this package is:

1. cd to the directory containing the package's source code and type ./configure to configure the package for your system. While running, configure prints some messages telling which features it is checking for. There are many options which you may provide to configure (which you can discover by running configure with the --help option).

2. Type make to compile the package.

3. Type make install to install the programs, libraries and any data files and documentation.

Documentation

The library is distributed with detailed documentation. The documentation in HTML format is stored in sub-folder named doc.

Example

This example creates an `expression_t' structure and calls solving routine exp_solve(). After the expression is solved, this routine prints the result and cleans up all previously allocated data.

#include <libexpression.h>

int main( int argc, char *argv[]){
	expression_t *exp;     //A structure that stores libexpression private data.
	char error[EXP_ERLEN]; //A buffer where solving routine may store error messages. This buffer must be large enough.
	int error_pos;         //Solving routine will store error position (if error occurs) in this variable.
	exp_error_t ercode;    //Solving routine will store error code (if error occurs) in this variable.
	exp_value_t *v;        //Pointer to a structure containing result.
	char *result;          //Pointer to a buffer with the result converted to a string
	int ret=0;

	//Create expression object
	if(NULL==( exp=exp_create( "4/1-4/3+4/5-4/7+4/9-4/11+4/13-4/15+4/17-4/19+4/21", 
			&ercode, error, &error_pos))){
		ret=1;

	}else{
		//Pass expression object to a solving routive ang get result
		if(NULL ==(v=exp_solve( exp, &ercode, error, &error_pos))){
			ret=1;

		}else{
			//Solving routine returned result. That means, no error occured.
			//Display the result to the user.
			result=exp_value_to_string( v);

			if( result){
				printf("%s\n", result);

			}else{
				printf( error, 
					"Result is invalid (e.g. result type is invalid or memory error)\n");
				error_pos=-1;
				ret=1;
			}
			//Free result structure
			exp_value_free( v);
		}
		//Free expression private data
		exp_free( exp);
	}

	//If any error occured while expression object was created
	//or expression was solved, then `ret' variable is set to 1
	//in this module. We check this variable and if it is set,
	//then we display error message to the user
	if( ret){
		fprintf( stderr, "%s\n", error);
	}
	return ret;
}

See file expression.c for more complicated example. To build this file, run gcc -o expression expression.c -lexpression in console.

Author

Sergey Kolotsey kolotsey@gmail.com

Copyright Notice

Libexpression is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

Libexpression is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public Licenise along with libexpression. If not, see http://www.gnu.org/licenses/.