Spread

A Calca-inspired TUI calculator/editor that combines vim-style text editing with live mathematical evaluation. Built in Rust using ratatui and powered by the Monkey programming language interpreter.

Features

Vim-style modal editing: Full vim modal editing support including normal, insert, visual, and command modes
Live mathematical evaluation: Write expressions and see results update in real-time using the => operator
Unit conversions: Convert between common units (km to miles, kg to lbs, celsius to fahrenheit, etc.)
Time functions: Built-in now() and utc() functions for current time calculations
Variable support: Define and use variables throughout your document
Function definitions: Create reusable functions using Monkey language syntax
Persistent evaluation: Variables maintain their values throughout the document
Split-pane interface: Editor on the left, calculation results on the right

Installation

Prerequisites

Rust (nightly toolchain recommended)
Nix with flakes enabled (optional, for development environment)
direnv (optional but recommended)

Building from source

git clone https://github.com/JonnyWalker81/spread.git
cd spread
cargo build --release

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

With Nix

If you have Nix with flakes enabled:

git clone https://github.com/JonnyWalker81/spread.git
cd spread
direnv allow  # If using direnv
just build    # Or: cargo build --release

Usage

Interactive Mode (TUI)

spread [file.spread]

Evaluation Mode (CLI)

spread --eval file.spread

Key Bindings

Normal Mode

i - Enter insert mode
v - Enter visual mode
: - Enter command mode
h/j/k/l - Navigate (vim motions)
w/b - Word navigation
0/$ - Line start/end
gg/G - Document start/end
dd - Delete line
yy - Yank line
p - Paste
u - Undo
Ctrl+r - Redo

Command Mode

:w - Save file
:q - Quit
:wq - Save and quit
:q! - Quit without saving

Examples

Basic Calculations

5 + 3 => 8
10 * 20 => 200
100 / 4 => 25
2^8 => 256

Variables

distance = 150
time = 2.5
speed = distance / time => 60

Unit Conversions

2km to miles => 1.242742
70kg to lbs => 154.3234
32f to c => 0
100c to f => 212
5 liters to gallons => 1.32086

Functions

# Define a function
calculate_tip = fn(bill, percent) { bill * percent / 100 }
bill_amount = 85.50
tip = calculate_tip(bill_amount, 20) => 17.1
total = bill_amount + tip => 102.6

# Using arrays
numbers = [1, 2, 3, 4, 5]
sum = fn(arr) { 
    if (len(arr) == 0) { 
        0 
    } else { 
        arr[0] + sum(rest(arr)) 
    }
}
total = sum(numbers) => 15

Time Functions

current_time = now() => 2025-07-20 17:21:12
utc_time = utc() => 2025-07-21 00:21:12 UTC

# Time-based calculations
start_hour = 9
current_hour = 17
hours_worked = current_hour - start_hour => 8
hourly_rate = 25
pay = hours_worked * hourly_rate => 200

Percentage Calculations

price = 150
discount = 20%
discount_amount = price * discount => 30
final_price = price - discount_amount => 120

Configuration

Configuration is stored in ~/.config/spread/config.toml:

[editor]
tab_size = 4
use_spaces = true  
line_numbers = true
wrap_lines = false

[ui]
theme = "default"
split_ratio = 0.6
show_line_numbers = true

[evaluator]
auto_evaluate = true
evaluation_delay_ms = 500
max_iterations = 1000
precision = 10

Development

This project uses a Nix flake for reproducible development environments.

Common Development Commands

# With just (task runner)
just build               # Development build
just build-release       # Release build  
just run                 # Run application
just test               # Run tests
just fmt                # Format code
just lint               # Run clippy
just watch              # Watch for changes

# With cargo directly
cargo build
cargo run -- file.spread
cargo test
RUST_LOG=spread=debug cargo run  # With debug logging

Debug Logging

In eval mode: RUST_LOG=spread=debug spread --eval file.spread
In TUI mode: RUST_LOG=spread=debug spread (logs written to spread.log)

Project Structure

spread/
├── src/
│   ├── main.rs         # Application entry point
│   ├── app.rs          # Main application state and event loop
│   ├── editor/         # Vim-style editor implementation
│   ├── evaluator/      # Mathematical expression evaluation
│   ├── interpreter/    # Monkey language interpreter
│   ├── document/       # Document model and persistence
│   ├── ui/             # Terminal UI components
│   └── config.rs       # Configuration management
├── flake.nix           # Nix development environment
├── Cargo.toml          # Rust dependencies
├── justfile            # Development task automation
└── CLAUDE.md           # AI assistant instructions

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

MIT License

JonnyWalker81/spread

README