Module resolver 

Reference resolution (P1.3, issue #525).

Core is the language: it parses formulas and evaluates them, but it has no notion of a sheet, a grid, or a named range. Resolver is the seam through which an embedding application (the workbook crate, a host app, a test harness) supplies the value a Ref points at.

The evaluator calls Resolver::resolve every time a formula reads a reference that is not already bound as a local variable (e.g. a LAMBDA parameter). The resolver owns all workbook semantics:

• a cross-sheet cell ref to a missing sheet -> ErrorKind::Ref (#REF!),
• a bare name that is not a defined name -> ErrorKind::Name (#NAME?),
• an empty cell -> Value::Empty,
• a range -> Value::Array of the cells in reading order.

Core never invents these; it simply forwards the Ref and returns whatever the resolver decides.

use std::collections::HashMap;
use truecalc_core::{Engine, Ref, Resolver, Value};

/// A resolver backed by a flat map keyed by canonical reference text.
struct MapResolver(HashMap<String, Value>);

impl Resolver for MapResolver {
    fn resolve(&mut self, r: &Ref) -> Value {
        self.0.get(&r.to_string()).cloned().unwrap_or(Value::Empty)
    }
}

let mut cells = HashMap::new();
cells.insert("Data!A1".to_string(), Value::Number(10.0));
cells.insert("Data!B1".to_string(), Value::Number(5.0));
let mut resolver = MapResolver(cells);

let engine = Engine::sheets();
let result = engine.evaluate_with_resolver("=Data!A1+Data!B1", &mut resolver);
assert_eq!(result, Value::Number(15.0));

Traits

Resolver

Resolves a Ref to the Value it points at.

Functions

extract_refs

Collect every Ref a formula reads, in left-to-right source order, without re-parsing – the input that lets the workbook build a dependency graph (plan section 3.2).