Struct LetFn 

pub struct LetFn;

Trait Implementations

impl Debug for LetFn

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

Formats the value using the given formatter.

impl Function for LetFn

Binds local names to values and evaluates a final expression with those bindings.

LET introduces lexical variables using name/value pairs, then returns the last expression.

Remarks

• Arguments must be provided as name, value pairs followed by one final calculation expression.
• Names are resolved as local identifiers and can shadow workbook-level names.
• Bindings are evaluated left-to-right, so later values can reference earlier bindings.
• Invalid names or malformed arity return #VALUE!.

Examples

title: "Bind intermediate values"
formula: "=LET(rate,0.08,price,125,price*(1+rate))"
expected: 135

title: "Use LET with range calculations"
grid:
  A1: 10
  A2: 4
formula: "=LET(total,SUM(A1:A2),total*2)"
expected: 28

title: "Nested LET supports shadowing"
formula: "=LET(x,2,LET(x,5,x)+x)"
expected: 7

related:
  - LAMBDA
  - IF
  - SUM
  - INDEX
faq:
  - q: "Can a LET binding reference a name defined later in the same LET?"
    a: "No. LET evaluates name/value pairs left-to-right, so each binding can only use earlier bindings."
  - q: "Does LET overwrite workbook or worksheet names permanently?"
    a: "No. LET names are lexical and local to that formula evaluation; they only shadow outer names inside the LET expression."
  - q: "Is LET itself volatile?"
    a: "No. LET is deterministic unless one of its bound expressions calls a volatile function such as RAND."

[formualizer-docgen:schema:start] Name: LET Type: LetFn Min args: 3 Max args: variadic Variadic: true Signature: LET() Arg schema: <unavailable: arg_schema panicked> Caps: PURE, SHORT_CIRCUIT [formualizer-docgen:schema:end]

fn caps(&self) -> FnCaps

Capability flags for this function

fn name(&self) -> &'static str

fn min_args(&self) -> usize

fn variadic(&self) -> bool

fn dispatch<'a, 'b, 'c>( &self, args: &'c [ArgumentHandle<'a, 'b>], ctx: &dyn FunctionContext<'b>, ) -> Result<CalcValue<'b>, ExcelError>

Dispatch to the unified evaluation path with automatic argument validation.

fn eval<'a, 'b, 'c>( &self, args: &'c [ArgumentHandle<'a, 'b>], _ctx: &dyn FunctionContext<'b>, ) -> Result<CalcValue<'b>, ExcelError>

The unified evaluation path.

fn namespace(&self) -> &'static str

fn volatile(&self) -> bool

fn arg_schema(&self) -> &'static [ArgSchema]

fn aliases(&self) -> &'static [&'static str]

Optional list of additional alias names (case-insensitive) that should resolve to this function. Default: empty slice. Implementors can override to expose legacy names. Returned slice must have ’static lifetime (typically a static array reference).

fn function_salt(&self) -> u64

fn eval_reference<'a, 'b, 'c>( &self, _args: &'c [ArgumentHandle<'a, 'b>], _ctx: &dyn FunctionContext<'b>, ) -> Option<Result<ReferenceType, ExcelError>>

Optional reference result path. Only called by the interpreter/engine when the callsite expects a reference (e.g., range combinators, by-ref argument positions, or spill sources).