Struct FactFn 

pub struct FactFn;

Trait Implementations

impl Debug for FactFn

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

Formats the value using the given formatter.

impl Function for FactFn

Returns the factorial of a non-negative integer.

FACT truncates fractional inputs toward zero before computing the factorial.

Remarks

• Non-numeric values that cannot be coerced return #VALUE!.
• Negative inputs return #NUM!.
• Results above 170! overflow Excel-compatible limits and return #NUM!.

Examples

title: "Basic factorial"
formula: "=FACT(5)"
expected: 120

title: "Fractional input is truncated"
formula: "=FACT(5.9)"
expected: 120

title: "Negative input returns numeric error"
formula: "=FACT(-1)"
expected: "#NUM!"

related:
  - FACTDOUBLE
  - GAMMALN
  - COMBIN
faq:
  - q: "Why does FACT(171) return #NUM!?"
    a: "Excel-compatible factorial support is capped at 170!; larger values overflow and return #NUM!."
  - q: "Does FACT round fractional inputs?"
    a: "No. It truncates toward zero before computing the factorial."

[formualizer-docgen:schema:start] Name: FACT Type: FactFn Min args: 1 Max args: 1 Variadic: false Signature: FACT(arg1: number@scalar) Arg schema: arg1{kinds=number,required=true,shape=scalar,by_ref=false,coercion=NumberLenientText,max=None,repeating=None,default=false} Caps: PURE [formualizer-docgen:schema:end]

fn caps(&self) -> FnCaps

Capability flags for this function

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

fn min_args(&self) -> usize

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

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

The unified evaluation path.

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

fn variadic(&self) -> bool

fn volatile(&self) -> bool

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).

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.