Struct WeeknumFn 

pub struct WeeknumFn;

Returns the week number of the year for a date serial.

Remarks

• Default return_type is 1 (week starts on Sunday).
• Supported return_type values are 1, 2, 11-17, and 21 (ISO week numbering).
• Unsupported return_type values return #NUM!.
• Input serials are interpreted using Excel 1900 date mapping rather than workbook 1904 interpretation.

Examples

title: "Default week numbering"
formula: "=WEEKNUM(45292)"
expected: 1

title: "ISO week numbering"
formula: "=WEEKNUM(42370, 21)"
expected: 53

related:
  - WEEKDAY
  - ISOWEEKNUM
  - DATE
faq:
  - q: "What is special about return_type 21 in WEEKNUM?"
    a: "return_type=21 switches to ISO week numbering, matching ISOWEEKNUM behavior."

Trait Implementations

impl Debug for WeeknumFn

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

Formats the value using the given formatter.

impl Function for WeeknumFn

[formualizer-docgen:schema:start] Name: WEEKNUM Type: WeeknumFn Min args: 1 Max args: variadic Variadic: true Signature: WEEKNUM(arg1: number@scalar, arg2…: number@scalar) Arg schema: arg1{kinds=number,required=true,shape=scalar,by_ref=false,coercion=NumberLenientText,max=None,repeating=None,default=false}; arg2{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 variadic(&self) -> bool

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 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.