01. What Froth Is

Froth is easiest to learn if you start with three laws from the accepted language spec:

1. The top level is a board of stable named slots.
2. Code only does a small number of things: read, bind, set, call, choose, and repeat.
3. Persistence remembers the overlay image, not the current execution.

That is the center of the language. Froth is not organized around a user-visible stack. It is organized around values, places, and a live image you can inspect and recover.

A Tiny Example

unit is 75

to pulse with pin [
  gpio.high: pin;
  ms: unit;
  gpio.low: pin
]

to blink with pin [
  repeat 3 [
    pulse: pin;
    ms: unit
  ]
]

blink: LED_BUILTIN

Read that as ordinary named code:

• unit is a top-level slot
• pulse and blink are top-level Code values
• repeat is a loop expression
• gpio.high and ms are base-image board bindings

If you redefine blink, old callers see the new definition because they still resolve through the same stable top-level slot.

What Makes It Different

Froth is built around a few current priorities:

• live interaction on the device
• coherent redefinition
• persistence and recovery
• transparent inspection

It deliberately keeps the public model named and lexical. In Froth, values are read by name, locals are lexical, and code is just another value.

The First Things To Keep In Your Head

• name is expr creates or rebinds a stable top-level slot.
• to name [...] is just sugar for binding a Code value.
• fn [...] creates anonymous Code.
• save, restore, and dangerous.wipe operate on the overlay image.
• The device is the real environment. Host tools help you get there faster.

Next: Getting started .