On

Struct On 

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pub struct On<'w, 't, E, B = ()>
where E: Event, B: Bundle,
{ /* private fields */ }
Expand description

A system parameter used by an observer to process events. See Observer and Event for examples.

On contains the triggered Event data for a given run of an Observer. It also provides access to the Trigger, which for things like EntityEvent with a PropagateEntityTrigger, includes control over event propagation.

The generic B: Bundle is used to further specialize the events that this observer is interested in. The entity involved does not have to have these components, but the observer will only be triggered if the event matches the components in B.

This is used to to avoid providing a generic argument in your event, as is done for Add and the other lifecycle events.

Providing multiple components in this bundle will cause this event to be triggered by any matching component in the bundle, rather than requiring all of them to be present.

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impl<'w, 't, E, B> On<'w, 't, E, B>
where E: Event, B: Bundle,

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pub fn new( event: &'w mut E, observer: Entity, trigger: &'w mut <E as Event>::Trigger<'t>, trigger_context: &'w TriggerContext, ) -> On<'w, 't, E, B>

Creates a new instance of On for the given triggered event.

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pub fn event_key(&self) -> EventKey

Returns the event type of this On instance.

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pub fn event(&self) -> &E

Returns a reference to the triggered event.

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pub fn event_mut(&mut self) -> &mut E

Returns a mutable reference to the triggered event.

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pub fn event_ptr(&self) -> Ptr<'_>

Returns a pointer to the triggered event.

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pub fn trigger(&self) -> &<E as Event>::Trigger<'t>

Returns the Trigger context for this event.

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pub fn trigger_mut(&mut self) -> &mut <E as Event>::Trigger<'t>

Returns the mutable Trigger context for this event.

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pub fn observer(&self) -> Entity

Returns the Entity of the Observer of the triggered event. This allows you to despawn the observer, ceasing observation.

§Examples

#[derive(EntityEvent)]  
struct AssertEvent {
    entity: Entity,
}

fn assert_observer(event: On<AssertEvent>) {  
    assert_eq!(event.observer(), event.entity);  
}  

let mut world = World::new();  
let entity = world.spawn(Observer::new(assert_observer)).id();  

world.trigger(AssertEvent { entity });  
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pub fn caller(&self) -> MaybeLocation

Returns the source code location that triggered this observer, if the track_location cargo feature is enabled.

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impl<'w, 't, E, B> On<'w, 't, E, B>
where E: EntityEvent, B: Bundle,

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pub fn target(&self) -> Entity

👎Deprecated since 0.17.0: Call On::event() to access the event, then read the target entity from the event directly.

A deprecated way to retrieve the entity that this EntityEvent targeted at.

Access the event via On::event, then read the entity that the event was targeting. Prefer using the field name directly for clarity, but if you are working in a generic context, you can use EntityEvent::event_target.

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impl<'w, 't, const AUTO_PROPAGATE: bool, E, B, T> On<'w, 't, E, B>
where E: EntityEvent<Trigger<'a> = PropagateEntityTrigger<AUTO_PROPAGATE, E, T>> + for<'a> Event, B: Bundle, T: Traversal<E>,

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pub fn original_event_target(&self) -> Entity

Returns the original Entity that this EntityEvent targeted via EntityEvent::event_target when it was first triggered, prior to any propagation logic.

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pub fn propagate(&mut self, should_propagate: bool)

Enables or disables event propagation, allowing the same event to trigger observers on a chain of different entities.

The path an EntityEvent will propagate along is specified by the Traversal component defined in PropagateEntityTrigger.

EntityEvent does not propagate by default. To enable propagation, you must:

  • Enable propagation in EntityEvent using #[entity_event(propagate)]. See EntityEvent for details.
  • Either call propagate(true) in the first observer or in the EntityEvent derive add #[entity_event(auto_propagate)].

You can prevent an event from propagating further using propagate(false). This will prevent the event from triggering on the next Entity in the Traversal, but note that all remaining observers for the current entity will still run.

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pub fn get_propagate(&self) -> bool

Returns the value of the flag that controls event propagation. See propagate for more information.

Trait Implementations§

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impl<'w, 't, E, B> Debug for On<'w, 't, E, B>
where E: for<'a> Event + Debug, <E as Event>::Trigger<'a>: for<'a> Debug, B: Bundle,

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

Formats the value using the given formatter. Read more
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impl<'w, 't, E, B> Deref for On<'w, 't, E, B>
where E: Event, B: Bundle,

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type Target = E

The resulting type after dereferencing.
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fn deref(&self) -> &<On<'w, 't, E, B> as Deref>::Target

Dereferences the value.
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impl<'w, 't, E, B> DerefMut for On<'w, 't, E, B>
where E: Event, B: Bundle,

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fn deref_mut(&mut self) -> &mut <On<'w, 't, E, B> as Deref>::Target

Mutably dereferences the value.
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impl<E, B> SystemInput for On<'_, '_, E, B>
where E: Event, B: Bundle,

Used for ObserverSystems.

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type Param<'i> = On<'i, 'i, E, B>

The wrapper input type that is defined as the first argument to FunctionSystems.
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type Inner<'i> = On<'i, 'i, E, B>

The inner input type that is passed to functions that run systems, such as System::run.
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fn wrap( this: <On<'_, '_, E, B> as SystemInput>::Inner<'_>, ) -> <On<'_, '_, E, B> as SystemInput>::Param<'_>

Auto Trait Implementations§

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impl<'w, 't, E, B> Freeze for On<'w, 't, E, B>

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impl<'w, 't, E, B> RefUnwindSafe for On<'w, 't, E, B>

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impl<'w, 't, E, B> Send for On<'w, 't, E, B>
where <E as Event>::Trigger<'t>: Send,

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impl<'w, 't, E, B> Sync for On<'w, 't, E, B>
where <E as Event>::Trigger<'t>: Sync,

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impl<'w, 't, E, B> Unpin for On<'w, 't, E, B>
where B: Unpin,

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impl<'w, 't, E, B = ()> !UnwindSafe for On<'w, 't, E, B>

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T, U> AsBindGroupShaderType<U> for T
where U: ShaderType, &'a T: for<'a> Into<U>,

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fn as_bind_group_shader_type(&self, _images: &RenderAssets<GpuImage>) -> U

Return the T ShaderType for self. When used in AsBindGroup derives, it is safe to assume that all images in self exist.
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T, C, D> Curve<T> for D
where C: Curve<T> + ?Sized, D: Deref<Target = C>,

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fn domain(&self) -> Interval

The interval over which this curve is parametrized. Read more
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fn sample_unchecked(&self, t: f32) -> T

Sample a point on this curve at the parameter value t, extracting the associated value. This is the unchecked version of sampling, which should only be used if the sample time t is already known to lie within the curve’s domain. Read more
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fn sample(&self, t: f32) -> Option<T>

Sample a point on this curve at the parameter value t, returning None if the point is outside of the curve’s domain.
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fn sample_clamped(&self, t: f32) -> T

Sample a point on this curve at the parameter value t, clamping t to lie inside the domain of the curve.
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impl<C, T> CurveExt<T> for C
where C: Curve<T>,

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fn sample_iter( &self, iter: impl IntoIterator<Item = f32>, ) -> impl Iterator<Item = Option<T>>

Sample a collection of n >= 0 points on this curve at the parameter values t_n, returning None if the point is outside of the curve’s domain. Read more
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fn sample_iter_unchecked( &self, iter: impl IntoIterator<Item = f32>, ) -> impl Iterator<Item = T>

Sample a collection of n >= 0 points on this curve at the parameter values t_n, extracting the associated values. This is the unchecked version of sampling, which should only be used if the sample times t_n are already known to lie within the curve’s domain. Read more
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fn sample_iter_clamped( &self, iter: impl IntoIterator<Item = f32>, ) -> impl Iterator<Item = T>

Sample a collection of n >= 0 points on this curve at the parameter values t_n, clamping t_n to lie inside the domain of the curve. Read more
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fn map<S, F>(self, f: F) -> MapCurve<T, S, Self, F>
where F: Fn(T) -> S,

Create a new curve by mapping the values of this curve via a function f; i.e., if the sample at time t for this curve is x, the value at time t on the new curve will be f(x).
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fn reparametrize<F>(self, domain: Interval, f: F) -> ReparamCurve<T, Self, F>
where F: Fn(f32) -> f32,

Create a new Curve whose parameter space is related to the parameter space of this curve by f. For each time t, the sample from the new curve at time t is the sample from this curve at time f(t). The given domain will be the domain of the new curve. The function f is expected to take domain into self.domain(). Read more
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fn reparametrize_linear( self, domain: Interval, ) -> Result<LinearReparamCurve<T, Self>, LinearReparamError>

Linearly reparametrize this Curve, producing a new curve whose domain is the given domain instead of the current one. This operation is only valid for curves with bounded domains. Read more
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fn reparametrize_by_curve<C>(self, other: C) -> CurveReparamCurve<T, Self, C>
where C: Curve<f32>,

Reparametrize this Curve by sampling from another curve. Read more
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fn graph(self) -> GraphCurve<T, Self>

Create a new Curve which is the graph of this one; that is, its output echoes the sample time as part of a tuple. Read more
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fn zip<S, C>( self, other: C, ) -> Result<ZipCurve<T, S, Self, C>, InvalidIntervalError>
where C: Curve<S>,

Create a new Curve by zipping this curve together with another. Read more
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fn chain<C>(self, other: C) -> Result<ChainCurve<T, Self, C>, ChainError>
where C: Curve<T>,

Create a new Curve by composing this curve end-to-start with another, producing another curve with outputs of the same type. The domain of the other curve is translated so that its start coincides with where this curve ends. Read more
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fn reverse(self) -> Result<ReverseCurve<T, Self>, ReverseError>

Create a new Curve inverting this curve on the x-axis, producing another curve with outputs of the same type, effectively playing backwards starting at self.domain().end() and transitioning over to self.domain().start(). The domain of the new curve is still the same. Read more
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fn repeat(self, count: usize) -> Result<RepeatCurve<T, Self>, RepeatError>

Create a new Curve repeating this curve N times, producing another curve with outputs of the same type. The domain of the new curve will be bigger by a factor of n + 1. Read more
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fn forever(self) -> Result<ForeverCurve<T, Self>, RepeatError>

Create a new Curve repeating this curve forever, producing another curve with outputs of the same type. The domain of the new curve will be unbounded. Read more
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fn ping_pong(self) -> Result<PingPongCurve<T, Self>, PingPongError>

Create a new Curve chaining the original curve with its inverse, producing another curve with outputs of the same type. The domain of the new curve will be twice as long. The transition point is guaranteed to not make any jumps. Read more
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fn chain_continue<C>( self, other: C, ) -> Result<ContinuationCurve<T, Self, C>, ChainError>
where T: VectorSpace, C: Curve<T>,

Create a new Curve by composing this curve end-to-start with another, producing another curve with outputs of the same type. The domain of the other curve is translated so that its start coincides with where this curve ends. Read more
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fn samples( &self, samples: usize, ) -> Result<impl Iterator<Item = T>, ResamplingError>

Extract an iterator over evenly-spaced samples from this curve. Read more
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fn by_ref(&self) -> &Self

Borrow this curve rather than taking ownership of it. This is essentially an alias for a prefix &; the point is that intermediate operations can be performed while retaining access to the original curve. Read more
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fn flip<U, V>(self) -> impl Curve<(V, U)>
where Self: CurveExt<(U, V)>,

Flip this curve so that its tuple output is arranged the other way.
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impl<C, T> CurveResampleExt<T> for C
where C: Curve<T> + ?Sized,

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fn resample<I>( &self, segments: usize, interpolation: I, ) -> Result<SampleCurve<T, I>, ResamplingError>
where I: Fn(&T, &T, f32) -> T,

Resample this Curve to produce a new one that is defined by interpolation over equally spaced sample values, using the provided interpolation to interpolate between adjacent samples. The curve is interpolated on segments segments between samples. For example, if segments is 1, only the start and end points of the curve are used as samples; if segments is 2, a sample at the midpoint is taken as well, and so on. Read more
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fn resample_auto( &self, segments: usize, ) -> Result<SampleAutoCurve<T>, ResamplingError>

Resample this Curve to produce a new one that is defined by interpolation over equally spaced sample values, using automatic interpolation to interpolate between adjacent samples. The curve is interpolated on segments segments between samples. For example, if segments is 1, only the start and end points of the curve are used as samples; if segments is 2, a sample at the midpoint is taken as well, and so on. Read more
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fn resample_uneven<I>( &self, sample_times: impl IntoIterator<Item = f32>, interpolation: I, ) -> Result<UnevenSampleCurve<T, I>, ResamplingError>
where I: Fn(&T, &T, f32) -> T,

Resample this Curve to produce a new one that is defined by interpolation over samples taken at a given set of times. The given interpolation is used to interpolate adjacent samples, and the sample_times are expected to contain at least two valid times within the curve’s domain interval. Read more
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fn resample_uneven_auto( &self, sample_times: impl IntoIterator<Item = f32>, ) -> Result<UnevenSampleAutoCurve<T>, ResamplingError>

Resample this Curve to produce a new one that is defined by automatic interpolation over samples taken at the given set of times. The given sample_times are expected to contain at least two valid times within the curve’s domain interval. Read more
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impl<T, C> CurveWithDerivative<T> for C
where T: HasTangent, C: SampleDerivative<T>,

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fn with_derivative(self) -> SampleDerivativeWrapper<C>

This curve, but with its first derivative included in sampling. Read more
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impl<T> Downcast for T
where T: Any,

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fn into_any(self: Box<T>) -> Box<dyn Any>

Converts Box<dyn Trait> (where Trait: Downcast) to Box<dyn Any>, which can then be downcast into Box<dyn ConcreteType> where ConcreteType implements Trait.
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fn into_any_rc(self: Rc<T>) -> Rc<dyn Any>

Converts Rc<Trait> (where Trait: Downcast) to Rc<Any>, which can then be further downcast into Rc<ConcreteType> where ConcreteType implements Trait.
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Converts &Trait (where Trait: Downcast) to &Any. This is needed since Rust cannot generate &Any’s vtable from &Trait’s.
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Converts &mut Trait (where Trait: Downcast) to &Any. This is needed since Rust cannot generate &mut Any’s vtable from &mut Trait’s.
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fn into_any(self: Box<T>) -> Box<dyn Any>

Convert Box<dyn Trait> (where Trait: Downcast) to Box<dyn Any>. Box<dyn Any> can then be further downcast into Box<ConcreteType> where ConcreteType implements Trait.
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Convert Rc<Trait> (where Trait: Downcast) to Rc<Any>. Rc<Any> can then be further downcast into Rc<ConcreteType> where ConcreteType implements Trait.
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Convert &Trait (where Trait: Downcast) to &Any. This is needed since Rust cannot generate &Any’s vtable from &Trait’s.
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Convert &mut Trait (where Trait: Downcast) to &Any. This is needed since Rust cannot generate &mut Any’s vtable from &mut Trait’s.
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where T: Any + Send,

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Returns the argument unchanged.

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where W: MakeTypeWitness<Arg = T>, T: ?Sized,

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const WITNESS: W = W::MAKE

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where T: ?Sized,

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type Type = T

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Converts self into a Left variant of Either<Self, Self> if into_left is true. Converts self into a Right variant of Either<Self, Self> otherwise. Read more
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where F: FnOnce(&Self) -> bool,

Converts self into a Left variant of Either<Self, Self> if into_left(&self) returns true. Converts self into a Right variant of Either<Self, Self> otherwise. Read more
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type Target = T

🔬This is a nightly-only experimental API. (arbitrary_self_types)
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where R: RngCore + ?Sized,

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Return a random value via the StandardUniform distribution. Read more
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Return an iterator over random variates Read more
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where T: SampleUniform, R: SampleRange<T>,

Generate a random value in the given range. Read more
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Return a bool with a probability of numerator/denominator of being true. Read more
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where D: Distribution<T>,

Sample a new value, using the given distribution. Read more
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where D: Distribution<T>, Self: Sized,

Create an iterator that generates values using the given distribution. Read more
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where T: Fill + ?Sized,

Fill any type implementing Fill with random data Read more
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👎Deprecated since 0.9.0: Renamed to random to avoid conflict with the new gen keyword in Rust 2024.
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where T: SampleUniform, R: SampleRange<T>,

👎Deprecated since 0.9.0: Renamed to random_range
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👎Deprecated since 0.9.0: Renamed to random_bool
Alias for Rng::random_bool.
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👎Deprecated since 0.9.0: Renamed to random_ratio
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fn next_u32(&mut self) -> u32

Return the next random u32. Read more
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Return the next random u64. Read more
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fn fill_bytes(&mut self, dst: &mut [u8])

Fill dest with random data. Read more
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impl<T, C, D> SampleDerivative<T> for D
where T: HasTangent, C: SampleDerivative<T> + ?Sized, D: Deref<Target = C>,

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fn sample_with_derivative_unchecked(&self, t: f32) -> WithDerivative<T>

Sample this curve at the parameter value t, extracting the associated value in addition to its derivative. This is the unchecked version of sampling, which should only be used if the sample time t is already known to lie within the curve’s domain. Read more
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fn sample_with_derivative(&self, t: f32) -> Option<WithDerivative<T>>

Sample this curve’s value and derivative at the parameter value t, returning None if the point is outside of the curve’s domain.
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fn sample_with_derivative_clamped(&self, t: f32) -> WithDerivative<T>

Sample this curve’s value and derivative at the parameter value t, clamping t to lie inside the domain of the curve.
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where U: Into<T>,

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type Error = Infallible

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Return the next random u32.
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Return the next random u64.
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Fill dest entirely with random data.
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where Self: Sized,

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Wrap RNG with the UnwrapMut wrapper.
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where S: Into<Dispatch>,

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