Struct Context 

pub struct Context {
    pub vars: HashMap<String, Value>,
    pub now_serial: Option<f64>,
    pub now_utc_nanos: Option<i64>,
    pub rng_cell: Option<(u64, u32, u32, u32)>,
}

Holds the named variable bindings for a formula evaluation.

All keys are stored and looked up in uppercase, so variable names are case-insensitive (A1, a1, and A1 all refer to the same binding).

Fields

vars: HashMap<String, Value>

now_serial: Option<f64>

Pinned “now” for volatile date functions (NOW, TODAY), as a local-time spreadsheet serial datetime (integer part = day serial, fraction = time of day). None ⇒ the functions read the ambient local clock. Set via crate::Engine::evaluate_at (P1.4, issue #526).

now_utc_nanos: Option<i64>

Pinned “now” as an absolute UTC instant (nanoseconds since the Unix epoch), for the zone-aware TZNOW. None ⇒ TZNOW reads the ambient UTC clock. Set from the workbook’s timestamp_ms during recalc; distinct from now_serial (a tz-naive local serial for NOW/TODAY).

rng_cell: Option<(u64, u32, u32, u32)>

Per-cell RNG key for deterministic draws: (seed, sheet_index, row, col). Set by the workbook recalc loop; None for bare Engine::evaluate calls.

Implementations

impl Context

pub fn new(vars: HashMap<String, Value>) -> Self

Create a Context from a map of variable name → value. Keys are normalised to uppercase on insertion.

pub fn empty() -> Self

Create an empty Context with no variable bindings.

pub fn get(&self, name: &str) -> Value

Look up a variable by name (case-insensitive). Returns Value::Empty if not found.

pub fn lookup(&self, name: &str) -> Option<Value>

Look up a binding by name (case-insensitive), distinguishing an absent binding (None) from one explicitly bound to Value::Empty (Some(Value::Empty)). Used by the evaluator to decide whether a reference should fall through to the resolver.

pub fn set(&mut self, name: String, value: Value) -> Option<Value>

Insert or overwrite a binding. Returns the previous value if one existed.

pub fn remove(&mut self, name: &str)

Remove a binding. Used to restore context after lambda/let evaluation.

pub fn draw_rand(&self, draw_index: u32) -> f64

SplitMix64-based PRF: draw a value in [0,1) for the given draw index. Uses the per-cell key when available; falls back to SystemTime for bare Engine::evaluate calls (non-deterministic).

pub fn draw_rand_n(&self, count: usize) -> Vec<f64>

Draw count values in [0,1), each using its own draw_index.