Calculator Plugin

Help query: "What does the calculator plugin do?" / "How do I use the calculator?" / "How do I evaluate expressions in Volt?"

The calculator plugin (user/calculator.rs) provides an expression evaluator buffer. You write assignments and math expressions in an Input pane, evaluate them, and read results in an Output pane — without leaving the editor.

Package name	calculator
Module	user/calculator.rs
Buffer name	*calculator*
Buffer kind	calculator

What it does

1. Opens a split buffer with Input (writable) and Output (results) sections
2. Parses lines as comments (# …), assignments (name = expr), or expressions
3. Evaluates with a recursive-descent math engine (functions + constants)
4. Replaces the Output section with results when you evaluate
5. Supplies calculator-scoped autocomplete and hover for built-in functions/constants

Open the calculator

Action	How
Command	calculator.open (command palette)
Typical leader path	via picker / command palette (F3)

calculator.open

Evaluate and switch panes

Command	Description	Default chord
calculator.evaluate	Evaluate Input → write results to Output	Ctrl+c Ctrl+c
calculator.switch-pane	Focus Input ↔ Output	Ctrl+Tab

Bindings apply in the Workspace scope while the calculator buffer is active. Evaluate emits the host hook plugin.evaluate; the user library handler id is calculator.evaluate-buffer.

Example session

Initial Input content looks like:

# Write expressions below. Press Ctrl+c Ctrl+c to evaluate…
a = 1
b = 2
sqrt(a + b)

Press Ctrl+c Ctrl+c. Output shows the evaluated results. Change values, evaluate again.

Language surface

Supported ideas (see user/calculator.rs for the full implementation):

• Arithmetic operators and parentheses
• Assignments reused by later lines
• Functions such as sqrt, trig, logs, pow, and related helpers
• Constants such as pi, e, tau, inf, nan
• # line comments

Autocomplete and hover providers are limited to calculator buffers so they do not compete with LSP elsewhere.

Commands reference

Command	Description
calculator.open	Open the calculator buffer in the active pane
calculator.evaluate	Evaluate input and replace the Output section
calculator.switch-pane	Switch focus between Input and Output

Related pages

• Builtin plugin catalog
• Create a plugin — calculator is the reference buffer+evaluator pattern
• Autocomplete providers