CrabCulator

A terminal-based calculator with a text-editor experience

Features • Installation • Usage • Syntax • License

---

Overview

Crabculator is a terminal-based calculator application that provides a text-editor-like experience for writing and evaluating math expressions. Write multiple lines of calculations, define variables, and see results update live as you type.

Features

• TUI — terminal-based user interface
• Real-time evaluation — Results update instantly as you type
• Variable support — Define variables (e.g., a = 5 + 3)
• Math functions — Built-in functions like sqrt, sin, cos, tan, log, ln, abs, floor, ceil
• Constants — Access pi and e directly in expressions
• Inline error display — Red underlined tokens with clear error explanations
• Full editor navigation — Cursor movement and editing anywhere in the document
• Session persistence — Variables persist across sessions

Installation

From source

Requires Rust 2024 edition.

git clone https://github.com/marconae/crabculator.git
cd crabculator
cargo install --path .

The binary will be available at target/release/crabculator.

Usage

Launch the application:

crabculator

Keyboard shortcuts

Key	Action
Arrow keys	Move cursor
Home / End	Jump to line start/end
Ctrl+H	Toggle help overlay
Ctrl+R	Clear buffer
Ctrl+C / Ctrl+Q	Exit

Expression Syntax

Basic arithmetic

5 + 3          → 8
10 - 4         → 6
6 * 7          → 42
15 / 3         → 5
17 % 5         → 2
(5 + 3) * 2    → 16

Variables

a = 5 + 3      → 8
b = a * 2      → 16
total = a + b  → 24

Variables persist across sessions and are stored in ~/.crabculator/state.json.

Built-in functions

Category	Function	Description
Basic	sqrt(x)	Square root
	cbrt(x)	Cube root
	abs(x)	Absolute value
	pow(base, exp)	Power
Trig	sin(x), cos(x), tan(x)	Trigonometric (radians)
	asin(x), acos(x), atan(x)	Inverse trigonometric
	atan2(y, x)	Two-argument arctangent
Hyperbolic	sinh(x), cosh(x), tanh(x)	Hyperbolic functions
	asinh(x), acosh(x), atanh(x)	Inverse hyperbolic
Log/Exp	ln(x)	Natural logarithm
	log(x), log10(x)	Base-10 logarithm
	log2(x)	Base-2 logarithm
	exp(x)	Exponential (e^x)
	exp2(x)	Power of 2 (2^x)
Rounding	floor(x), ceil(x)	Round down/up
	round(x)	Round to nearest
Utility	min(a, b), max(a, b)	Minimum/maximum
	hypot(a, b)	Hypotenuse (sqrt(a² + b²))

Constants

Constant	Value
pi	3.14159...
e	2.71828...

Example session

radius = 5
area = pi * radius^2    → 78.5398...
circumference = 2 * pi * radius    → 31.4159...

a = 3
b = 4
hypotenuse = sqrt(a^2 + b^2)    → 5

License

Free and open-source under MIT.

---

Build with 🦀 Rust and made with ❤️ by marconae – blogging on deliberate.codes.