Crate xxcalc [] [src]

xxcalc is a crate which provides an embeddable floating-point polynomial calculator and linear solver.

You can use xxcalc to embed mathematical expression evaluator in your own programs. By default the calculator provides addition +, subtraction -, multiplication *, division / and exponentation ^ operators. Some functions such as log and log10 are implemented, as well as pi and e constants. This is a polynomial calculator, so you can perform arithmetic operations on polynomials (using x symbol by default) - a simple floating-point number is just a special case of a polynomial (the constant polynomial, polynomial of degree zero).

Furthermore the crate is well structurized and documented - you can use pieces it provides to create your own custom solutions (you can use or change a tokenizer, parser and evaluator however you want). Look at implementations of PolynomialParser, LinearSolverParser, PolynomialEvaluator or LinearSolverEvaluator to see how to extend default implementations.

With the crate a xxcalc binary is provided which can be used as a standalone CLI calculator (which can be replacement for bc command). If the crate is installed with a feature "interactive" enabled, a history of commands is enabled.

Whole library is meticulously tested, use cargo test to run unit tests (including doc examples), cargo bench will run simple benchmarks, while cargo bench -- --ignored will run more computation-heavy benchmarks.


You can easily take a LinearSolver or PolynomialCalculator to embed mathematical engine inside your programs.

use xxcalc::linear_solver::LinearSolver;
use xxcalc::calculator::Calculator;
use xxcalc::polynomial::Polynomial;

assert_eq!(LinearSolver.process("2x + 1 = 2(1-x)"), Ok(Polynomial::constant(0.25)));
assert_eq!(LinearSolver.process("0.1*-2+4"), Ok(Polynomial::constant(3.8)));

Please see documentation for PolynomialCalculator for more examples.



Calculator is an easy to use generic method of evaluating string expressions.


Evaluator is a TokensReducer, it takes token in RPN form and evaluates its Polynomial value.


Defines a LinearSolver which extends a PolynomialCalculator with ability of solving single linear equation.


Parser is a TokensProcessor, it takes Tokens in a classical infix form and transforms them into Reverse Polish Notation form for further evaluation.


Defines Polynomial expression with basic operators on it.


Defines a PolynomialCalculator with common arithmetic operations, functions and constants already defined.


Tokenizer is a StringProcessor, it takes string expression and converts it into Tokens for further processing.



Tokens is a compound storage for list of tokens with their identifiers.



An error that occurs during token reduction, usually by an evaluator.


An error that occurs during token processing, usually by a parser.


Token is a basic unit returned after tokenization using a StringProcessor.



Transforms text expression into list of tokens.


Transforms list of tokens into another list of tokens.


Evaluates list of tokens into a single Polynomial value.

Type Definitions


Vector of unique identifiers.


List of tokens with their position.