Struct CompiledPredicate 

pub struct CompiledPredicate { /* private fields */ }

A predicate parsed once, testing tuples.

Implementations

impl CompiledPredicate

pub fn new(text: &str) -> Self

Parse text.

pub fn text(&self) -> &str

The predicate as written.

pub fn keeps( &self, tuple: &RuntimeTuple, scope: &dyn Lookup, ) -> Result<bool, RuntimeError>

Whether tuple, drawn in scope, passes: the predicate’s value is true. A predicate whose value is None keeps no tuple.

impl CompiledPredicate

pub fn is_total(&self, kind_of: &dyn Fn(&str) -> Option<ValueKind>) -> bool

Whether no evaluation of the predicate can fail over tuples whose elements have the kinds kind_of gives, None for an element of unknown or mixed kind (comprehension_forms.md §10.2 R5).

The answer is read off the predicate’s tree. ||, &&, and ! are total over operands that are total and have a truth value (a boolean or a number, never a string). ==, !=, and membership are total over total operands, since values of different kinds are unequal; an ordering comparison is total only when both sides are numbers, both strings, or both booleans. Arithmetic is total over numeric operands, dividing only by a non-zero constant. An element is total when its kind is known, a literal always is, and any other expression (a function call, a cast, a bitwise operator) can fail.

Trait Implementations

impl Clone for CompiledPredicate

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for CompiledPredicate

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

Formats the value using the given formatter.