sci-calc

An easy to use, fully functional scientific calculator library with command line interface.

$ sci-calc
2 + 2
 = 4
a = ans * pi
 = 12.566370614359172
cos(a)
 = 1
exit
$

Features

• Variable assignment and recall
• Comprehensive built-in functions and constants
• Command line interface with line-editing and history recall
• Elegant, verbose error handling

Library

Add this crate to your project using cargo:

cargo add sci-calc

Below is a quick program implementing the sci-calc crate, see the full documentation for details.

use std::io::stdin;
use sci_calc::{calculate, context::Context};

fn main() {
	let mut ctx = Context::new();
	loop {
		let mut input = String::new();
		std::io::stdin().read_line(&mut input).unwrap();
		match calculate(input.as_str(), &mut ctx) {
			Ok(result) => println!(" = {result}"),
			Err(e) => println!("{e}"),
		}
	}
}

Command Line Interface

To compile from source:

cargo build --release --bin sci-calc

This will compile the binary to target/release/sci-calc. Run the binary with an equation as an argument to evaluate that expression as a one-off, or run it with no arguments to use the calculator as a REPL. Use ctrl-C or the exit keyword to exit the program.

$ sci-calc 5 + 5
 = 10
$ sci-calc
5 + 5
 = 10
ans * 2
 = 20
exit
$

Content

Basic Arithmetic

5 + 5 * 2^3
 = 45
1.23e5 * 4.56e-6
 = 0.56088
20!
 = 2432902008176640000

Implemented operators in reverse order of precedence:

• Additive: +, -
• Multiplicative: *, /, % (modulus), // (floored divide)
• Exponentiation: ^
• Factorial: !

Variable recall

a = 1 + 1
 = 2
b = 2 * 2
 = 4
a + b
 = 6
ans + 4
 = 10

Builtins

Vars:

e
 = 2.718281828459045
2 * pi
 = 6.283185307179586
ans / 2
 = 3.141592653589793

Functions:

sqrt(2)
 = 1.4142135623730951
ln(e)
 = 1
2 * asin(1)
 = 3.141592653589793
stddev(1, 2, 3)
 = 0.816496580927726

All implemented functions:

• Square root sqrt(x) and n-root root(x, root)
• Factorial fac(x), same as ! operator
• Mean mean(x, y, ...) and standard deviation stddev(x, y, ...)
• Trig functions: sin(x), cos(x), and tan(x)
  • Inverse variants: asin(x), ...
  • Hyperbolic variants: sinh(x), ...
  • Inverse hyperbolic variants: asinh(x), ...
• Mininum min(x, y) and maximum max(x, y)
• Natural log ln(x), log base-10 log10(x), and log base-n log(x, base)
• Absolute value abs(), round round(), floor floor(), and ceiling ceil()

Errors

Parsing error examples

5 +
Parser error: Unexpected EOI

5 + + 5
Parser error: Unexpected token
| 5 + + 5
|     └── here

5@ + 5
Parser error: Invalid token
| 5@ + 5
|  └── here

Variable error examples

ans * 2
Calculation error: Cannot use 'ans' without a previous evaluated equation

pi = 3
Assignment error: Can't assign value to constant 'pi'

a + 5
Undefined identifier: Unknown variable 'a'