Enum Missing 

pub enum Missing<T> {
    Present(T),
    Absent,
}

Wrapper type that detects if an R argument was not passed (missing).

This corresponds to R’s missing() function. When a function parameter has type Missing<T>, it will be Missing::Absent if the caller didn’t provide that argument, or Missing::Present(value) if they did.

Example

use miniextendr_api::{miniextendr, Missing};

#[miniextendr]
fn maybe_square(x: Missing<f64>) -> f64 {
    match x {
        Missing::Present(val) => val * val,
        Missing::Absent => 0.0,
    }
}

In R:

maybe_square(5)  # 25
maybe_square()   # 0

Variants

Present(T)

The argument was provided.

Absent

The argument was not provided (missing in R).

Implementations

impl<T> Missing<T>

pub fn is_present(&self) -> bool

Returns true if the argument was provided.

pub fn is_missing(&self) -> bool

Returns true if the argument was not provided.

Named to match R’s missing() function.

pub fn into_option(self) -> Option<T>

Convert to Option<T>, returning None if missing.

pub fn as_ref(&self) -> Missing<&T>

Get a reference to the value if present.

pub fn as_mut(&mut self) -> Missing<&mut T>

Get a mutable reference to the value if present.

pub fn unwrap_or(self, default: T) -> T

Returns the contained value or a default.

pub fn unwrap_or_else<F: FnOnce() -> T>(self, f: F) -> T

Returns the contained value or computes it from a closure.

pub fn map<U, F: FnOnce(T) -> U>(self, f: F) -> Missing<U>

Maps Missing<T> to Missing<U> by applying a function.

pub fn unwrap(self) -> T

Returns the contained value, panicking if absent.

Panics

Panics if the value is Absent.

pub fn expect(self, msg: &str) -> T

Returns the contained value, panicking with a custom message if absent.

Panics

Panics with the provided message if the value is Absent.

impl<T: Default> Missing<T>

pub fn unwrap_or_default(self) -> T

Returns the contained value or the default for that type.

Trait Implementations

impl<T: Clone> Clone for Missing<T>

fn clone(&self) -> Missing<T>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T: Debug> Debug for Missing<T>

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

Formats the value using the given formatter.

impl<T> Default for Missing<T>

fn default() -> Self

The default is Absent.

impl<T: Eq> Eq for Missing<T>

#[doc(hidden)]

fn assert_fields_are_eq(&self)

🔬This is a nightly-only experimental API. (derive_eq_internals)

#[doc(hidden)]

fn assert_receiver_is_total_eq(&self)

👎Deprecated since 1.95.0:

implementation detail of #[derive(Eq)]

impl<T> From<Missing<T>> for Option<T>

fn from(missing: Missing<T>) -> Self

Converts to this type from the input type.

impl<T> From<Option<T>> for Missing<T>

fn from(opt: Option<T>) -> Self

Converts to this type from the input type.

impl<T> From<T> for Missing<T>

fn from(value: T) -> Self

Converts to this type from the input type.

impl<T: PartialEq> PartialEq for Missing<T>

fn eq(&self, other: &Missing<T>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T> TryFromSexp for Missing<T>

where T: TryFromSexp, <T as TryFromSexp>::Error: Into<SexpError>,

type Error = SexpError

The error type returned when conversion fails.

fn try_from_sexp(sexp: SEXP) -> Result<Self, Self::Error>

Attempt to convert an R SEXP to this Rust type.

unsafe fn try_from_sexp_unchecked(sexp: SEXP) -> Result<Self, Self::Error>

Convert from SEXP without thread safety checks.

impl<T: Copy> Copy for Missing<T>

impl<T> StructuralPartialEq for Missing<T>

Layout

Note: Unable to compute type layout, possibly due to this type having generic parameters. Layout can only be computed for concrete, fully-instantiated types.