Interactive Profile

This page covers the maintained prompt-facing and tool-facing interactive surface.

Prompt and Evaluation

REPL (interactive profile)

Layer: core
Behavior: Reads top-level forms, evaluates complete input, prints the result of top-level expression evaluation, and keeps the prompt alive on recoverable errors.
Example:

1 + 1

multiline forms (interactive profile)

Layer: core
Behavior: The board reads one line at a time, and one line holds one form. The editor, frothy send, and frothy connect send a form with line breaks as one line, so a block can span lines. In another serial terminal, write the whole form on one line, and separate its expressions with ;.
Example:

to pulse with pin [ gpio.high: pin; wait: 75; gpio.low: pin ]

Interrupts and Recovery

Ctrl-C (interactive profile)

Layer: core
Behavior: Interrupts the running evaluation and returns the prompt to a usable state. The evaluator checks for interrupts at safe points.
Example:

Press Ctrl-C during a loop.

safe boot (interactive profile)

Layer: core
Behavior: On an ESP32 board, Ctrl-C or the BOOT button in the 600 ms after start skips restore and boot, so a bad saved program cannot keep the prompt closed. An RP2040 board has no such window; Ctrl-C stops a boot that runs.
Example:

Press Ctrl-C in the safe-boot window. Then run `restore` and `see boot`, or run `dangerous.wipe`.

Inspection Commands

words, see, status (interactive profile)

Layer: core
Behavior: Inspect the live image through prompt-facing built-ins. words lists the names that exist, see renders a binding’s source form, and status reports the session and runtime.
Example:

words
see boot
see blink

Structured Tooling Sessions

frothy session --records (tooling session)

Layer: host tool
Behavior: Tools use the same prompt as a person; the device has no separate control mode. frothy session --records sends source to the prompt and writes one NDJSON record for each event: a send, a response, a refused form, an interrupt.
Example:

frothy session --records

extension-owned helper session (editor path)

Layer: host tool
Behavior: The VS Code extension starts one frothy session --records child process, and that process owns the serial port. There is no daemon and no second owner of the port in the maintained Frothy editor path. Example:

VS Code connect, send line, send file, interrupt, and simple inspection all go through that one session.

Capability Layers

The interactive surface is only one part of Frothy:

• the core language: values, names, calls, blocks, control flow, Cells, and Code
• the prompt: evaluation, multiline input, interrupts, inspection, save, and restore
• tooling sessions: editor and CLI control paths over the same device-owned image
• board words: GPIO, ADC, I2C, UART, PWM, and other hardware words when the current board firmware exposes them

For day-one work, you do not need to memorize those layers. You need the prompt, words, see, led.on:, led.off:, and a willingness to try one small line at a time.