#calculator #evaluator #math-parser #math

kalk

A math evaluator library that supports user-defined functions, variables and units, and can handle fairly ambiguous syntax

43 releases (27 stable)

3.2.0 Apr 3, 2024
3.1.0 Mar 23, 2024
3.0.4 Jul 20, 2023
3.0.3 Jan 24, 2023
0.2.0 Jun 18, 2020

#549 in Parser implementations

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68 downloads per month
Used in 2 crates

MIT and LGPL-3.0+

320KB
8K SLoC

kalk

Kalk is a math parser library that supports user-defined variables and functions. An example of what it can parse:

f(x, y) = sum(1, 3, (2sin4/x!)^y) + cos(n deg)
a = 3
f(a, 2)

>> 1.1899401098014355

Features

  • Operators: +, -, *, /, !
  • Groups: (), [], ⌈ceil⌉, ⌊floor⌋
  • Vectors: (x, y, z, ...)
  • Matrices: [x, y, z; a, b, c; ...]
  • Pre-defined functions and constants
  • User-defined functions and variables. f(x, y) = xy, x = 5
  • Root finding using Newton's method (eg. x^2 = 64). Note: estimation and limited to one root
  • Derivative of functions (derivatives of noisy functions or of higher order can be a bit inaccurate). f'(2), sin'(-pi)
  • Integration. (0, pi, sin(x) dx) or (0, π, sin(x) dx), maybe sometimes be slightly off
  • Understands fairly ambiguous syntax. Eg. 2sin50 + 2xy
  • Sum function: sum(start, to, expression) Eg. sum(1, 3, 2n+1) is the same as 2*1+1 + 2*2+1 + 2*3+1 = 15
  • Piecewise functions: f(x) = { f(x + 1) if x <= 1; x otherwise }, pressing enter before typing the final } will make a new line without submitting
  • Different number bases: Either with a format like 0b1101, 0o5.3, 0xff or a format like 1101_2. The latter does not support letters, as they would be interpreted as variables
  • Misc: separate expressions by a semicolon to write them on the same line, use the ans variable to get the value of the previously calculated expression

Rust Usage

use kalk::parser;
let mut parser_context = parser::Context::new();
let precision = 53;
let result = parser::eval(&mut parser_context, "5*3", precision).unwrap().unwrap();
assert_eq!(result.to_f64(), 15f64);

Using f64 instead of rug::Float

The cargo feature rug enables rug, and is used by default. If you disable this, kalk will use f64 instead, making it more portable.

Compiling

Make sure you have diffutils gcc make and m4 installed.

JavaScript Usage

const kalk = await import("@paddim8/kalk");
const context = new kalk.Context();
console.log(context.evaluate("2pi + 3").toScientificNotation().toString());

Dependencies

~4MB
~75K SLoC