03. Values and Expressions

You can learn a surprising amount about Frothy from one line:

2 * 3 + 4

This expression evaluates to 10. Frothy uses conventional operator precedence: *, /, and % bind tighter than + and -; comparisons come next; then and; then or. Operators in the same group associate from left to right.

2 * 3 + 4
(2 + 3) * 4
1 < 2 and 3 < 4

Those expressions yield 10, 20, and true. Parentheses are still welcome whenever they make the intended grouping easier to see.

The Value Set

A full Frothy profile can carry:

• Int, Bool, and Nil for small immediate values
• Text for immutable, byte-oriented text
• Cells for fixed-size indexed storage
• record values for data with named fields
• Code for executable behavior
• Bytes for transient working bytes
• Handle for a live platform resource such as PWM, UART, I2C, or TCP

Smaller profiles can leave out value families they cannot afford. The ESP32 plain profile exposes the full documented set.

Text, cells, records, and code can be part of a saved overlay. Bytes and Handle are deliberately live values: pack bytes into Text when you need a persistent copy, and reopen hardware resources from boot after restore. A handle is a tagged Frothy value, not a raw pointer or a disguised integer.

Names Hold The Conversation Together

At top level, a name refers to a stable slot:

speed is 75
speed is 120

That is a rebind, not a fresh variable floating in space. The top-level slot named speed is the same slot before and after the second line. What changed is the value currently stored there.

That matters for live work. If one piece of code calls pulse, and you later rebind pulse, callers that resolve through that top-level slot see the new behavior.

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

pulse: $led_builtin

to pulse with pin [
  gpio.high: pin;
  ms: 20;
  gpio.low: pin
]

The name is stable. The value changed. The image remains inspectable.

Calls Read Like Calls

Foreign bindings and Frothy definitions use the same call surface:

gpio.write: $led_builtin, 1
ms: 100
blink: $led_builtin, 3, 75

The callee appears before the colon. Arguments follow after the colon, separated by commas. A zero-argument call still uses the colon when you are asking for the code to run:

led.on:
millis:

Without the call, a name is a value lookup. That distinction lets you inspect or pass a Code value without running it.

Lookup Order

When Frothy sees a name, it searches:

1. the current local scope
2. enclosing local scopes
3. top-level slots

A local can shadow a top-level name:

speed is 75

demo is fn [
  here speed is 10;
  speed
]

Inside demo, speed means the local. Outside it, speed still means the top-level slot.

The reading habit is simple: name state you intend to keep, group expressions when it helps the story, and remember that a colon turns a name lookup into a call.

Next: Words and definitions .