Struct ListShape 

pub struct ListShape { /* private fields */ }

A shape that matches a list positionally, with an optional rest shape.

The leading items shapes must match the list elements in order. Without a rest shape the list length must match exactly (a tuple); with one, every trailing element must match the rest shape (a variadic list).

Examples

use sim_kernel::{Cx, DefaultFactory, Expr, NoopEvalPolicy};
use sim_shape::{ExprKind, ExprKindShape, ListShape, Shape};

let mut cx = Cx::new(Arc::new(NoopEvalPolicy), Arc::new(DefaultFactory));
let shape = ListShape::new(vec![Arc::new(ExprKindShape::new(ExprKind::String))]);
let expr = Expr::List(vec![Expr::String("hi".to_owned())]);
assert!(shape.check_expr(&mut cx, &expr).unwrap().accepted);
// an empty list rejects: the single positional item shape is unmatched.
assert!(!shape.check_expr(&mut cx, &Expr::List(vec![])).unwrap().accepted);

Implementations

impl ListShape

pub fn new(items: Vec<Arc<dyn Shape>>) -> Self

Build a fixed-length list shape over the given positional item shapes.

pub fn tuple(items: Vec<Arc<dyn Shape>>) -> Self

Build a fixed-length tuple shape; an alias for ListShape::new.

pub fn with_rest(items: Vec<Arc<dyn Shape>>, rest: Arc<dyn Shape>) -> Self

Build a list shape with leading items and a rest shape for the tail.

pub fn variadic(prefix: Vec<Arc<dyn Shape>>, rest: Arc<dyn Shape>) -> Self

Build a variadic list shape; an alias for ListShape::with_rest.

pub fn items(&self) -> &[Arc<dyn Shape>]

The positional item shapes.

pub fn rest(&self) -> Option<&Arc<dyn Shape>>

The rest shape applied to trailing elements, if this list is variadic.

Trait Implementations

impl Shape for ListShape

fn is_subshape_of( &self, cx: &mut Cx, parent: &dyn Shape, ) -> Result<Option<bool>>

Return a concrete implication answer when this shape owns the semantics.

fn check_value(&self, cx: &mut Cx, value: Value) -> Result<ShapeMatch>

Check a Value against this shape, yielding a ShapeMatch.

fn check_expr(&self, cx: &mut Cx, expr: &Expr) -> Result<ShapeMatch>

Check an Expr against this shape, yielding a ShapeMatch.

fn describe(&self, cx: &mut Cx) -> Result<ShapeDoc>

Produce the human-facing ShapeDoc for this shape.

fn id(&self) -> Option<ShapeId>

Stable ShapeId when this shape has runtime identity, else None.

fn symbol(&self) -> Option<Symbol>

Symbol naming this shape when it has one, else None.

fn parents(&self, _cx: &mut Cx) -> Result<Vec<Value>, Error>

Parent shapes for the subshape walk; empty by default.

fn is_effectful(&self) -> bool

Whether matching this shape may run effects; false by default.

fn is_total(&self) -> bool

Whether this shape accepts every input in its domain; false by default.