Crate taschenrechner[−][src]

`Taschenrechner` – Computer-Algebra-System

A CAS is an advanced symbolic calculator. It can evaluate, simplify, differentiate, integrate and solve algebraic expressions.

use cas::prelude::*;

fn main() {
    REPL::start();
}

Features

Warning: This is not yet feature-complete. See libqalculate for a better alternative.

REPL interface
Lex operators, functions, symbols, deciaml numbers
Parse expressions of infix notation into a expressions tree
Define variables and functions
Simplify expressions
Evaluate expressions to single numbers
Comprehensive notation-error messages

TODO

Arbitrary-precision arithmetic
Integrate, differentiate expressions
Solve single- and multi-variable equations / inequalities

Eval

The current eval is not very sophisticated. It is functional, but can’t simplify any expressions, if a subexpression remains unresolved.

REPL

This crate comes with an interactive comand-line-interface: Read-Eval-Print-Loop.

Built-in functions and constants

(for a full complete list see default_env.txt)

π (pi), τ (tau), e (eurler’s number), inf (infinity), nan (not a number)
trigonometric functions: sin, cos, tan, their inverse and hyperbole
abs, ceil, floor, trunc, fract

How to build see Cargo for Rust

4.3 - π^2 = sin y is an algebraic expression. It consists of atoms (4.3, π, 2, y) and operators (-, ^, =, sin). Operators manipulate atoms. We normally write such expressions in infix-notaion, where one has to know the precedence and associativity of an operator. The exponent (^) must be evaluated before the the substraction (-), evon though it appears later. To evaluate the expression linearly, it has to be converted into polish noation, which is basicly a single function call of function calls (= - 4.3 ^ π 2 sin y).

Lexer and parser

To evaluate the string of an expression, it undergoes 3 steps:

Lexer the string is split up into tokens (4.3, -, π, ^, 2, =, sin, y)
Parser the stream of tokens will be ordered into polish notation
Eval the expression tree can now be evaluated recursively

Modules

prelude

The prelude module contains all the types to get you started.