Struct Placed 

pub struct Placed {
    pub program: Program,
    pub roles: Roles,
    pub wire_id: String,
    pub placement: Solution,
    pub graph: Graph,
    pub render: Decision,
    pub kind: Kind,
}

A program with its signal graph sliced into the roles the runtime drives.

Fields

program: Program

roles: Roles

wire_id: String

A content-derived id for the command channel, per §4.3: “a stable, content-derived operation id (sha256(module, name, signature)[..16]) — not a URL a human maintains, and stable across refactors that don’t change the signature.”

placement: Solution

How stage 7 placed the program, kept so that beck explain place prints the derivation rather than re-deriving it from a second, drifting copy.

graph: Graph

The signal graph itself, kept so that beck explain flow, the incremental analysis and any later view engine read what the slicer read rather than re-deriving it.

render: Decision

Where this program’s component renders, and what follows (crate::render). Decided here because the fact it turns on — whether the sliced view reads the session — is this module’s to know.

kind: Kind

Whether this is an application or a library — a module with no merge point, whose Placed::roles are placeholders rather than a slice of anything.

A library used to have no Placed at all, which meant it had no way to run its own tests (docs/22 §22.6, docs/25 §25.6 item 1): every SICP exercise is a library, and so is every domain module a real project would most want unit tests for. It has one now — but a placeholder role is a lie a caller must not be able to tell by accident, so the flag is on the struct and Placed::is_application is what the paths that drive a program ask.

Implementations

impl Placed

pub fn is_application(&self) -> bool

pub fn library(program: Program, graph: Graph, wire_id: String) -> Placed

A module with no merge point, wrapped so that the parts of the toolchain that do not need one can still reach it.

The four roles are placeholders and they are chosen to be inert rather than plausible: the fold returns its accumulator unchanged, validate refuses everything, the view renders nothing and the initial state is unit. Nothing should ever call them — Kind::Library is the flag that says so, and beck test refuses a given, a when or a page expectation against a library by name rather than running one of these and reporting a confusing pass.

Trait Implementations

impl Clone for Placed

fn clone(&self) -> Placed

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Placed

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.