Struct BesselIFn 

pub struct BesselIFn;

Returns the modified Bessel function In(x).

Computes the modified Bessel function of the first kind for a real value x and a non-negative integer order n. The order is truncated toward zero, matching spreadsheet behavior.

Remarks

• Arguments are supplied as BESSELI(x, n).
• n must truncate to a non-negative integer order.
• Invalid domains or non-finite results return #NUM!.

title: "First-order modified Bessel I"
formula: "=BESSELI(0.5,1)"
expected: 0.2578943053908963

title: "Order is truncated"
formula: "=BESSELI(0.5,1.9)"
expected: 0.2578943053908963

related:
  - BESSELJ
  - BESSELK
  - BESSELY
faq:
  - q: "What happens to fractional order values?"
    a: "The order argument is truncated toward zero before evaluation."

Trait Implementations

impl Debug for BesselIFn

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

Formats the value using the given formatter.

impl Function for BesselIFn

[formualizer-docgen:schema:start] Name: BESSELI Type: BesselIFn Min args: 2 Max args: 2 Variadic: false Signature: BESSELI(arg1: any@scalar, arg2: any@scalar) Arg schema: arg1{kinds=any,required=true,shape=scalar,by_ref=false,coercion=None,max=None,repeating=None,default=false}; arg2{kinds=any,required=true,shape=scalar,by_ref=false,coercion=None,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>], _ctx: &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 dependency_contract( &self, _arity: usize, ) -> Option<FunctionDependencyContract>

Optional dependency contract for passive planning/FormulaPlane analysis.

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.