[][src]Struct proptest::sample::Index

pub struct Index(_);

A stand-in for an index into a slice or similar collection or conceptually similar things.

At the lowest level, Index is a mechanism for generating usize values in the range [0..N), for some N whose value is not known until it is needed. (Contrast with using 0..N itself as a strategy, where you need to know N when you define the strategy.)

For any upper bound, the actual index produced by an Index is the same no matter how many times it is used. Different upper bounds will produce different but not independent values.

Shrinking will cause the index to binary search through the underlying collection(s) it is used to sample.

Note that Index cannot currently be used as a slice index (e.g., slice[index]) due to the trait coherence rules.


If the collection itself being indexed is itself generated by a strategy, you can make separately define that strategy and a strategy generating one or more Indexes and then join the two after input generation, avoiding a call to prop_flat_map().

use proptest::prelude::*;

proptest! {
    fn my_test(
        names in prop::collection::vec("[a-z]+", 10..20),
        indices in prop::collection::vec(any::<prop::sample::Index>(), 5..10)
    ) {
        // We now have Vec<String> of ten to twenty names, and a Vec<Index>
        // of five to ten indices and can combine them however we like.
        for index in &indices {
            println!("Accessing item by index: {}", names[index.index(names.len())]);
            println!("Accessing item by convenience method: {}", index.get(&names));
        // Test stuff...


impl Index[src]

pub fn index(&self, size: usize) -> usize[src]

Return the real index that would be used to index a collection of size size.


Panics if size == 0.

pub fn get<'a, T>(&self, slice: &'a [T]) -> &'a T[src]

Return a reference to the element in slice that this Index refers to.

A shortcut for &slice[index.index(slice.len())].

pub fn get_mut<'a, T>(&self, slice: &'a mut [T]) -> &'a mut T[src]

Return a mutable reference to the element in slice that this Index refers to.

A shortcut for &mut slice[index.index(slice.len())].

Trait Implementations

impl Arbitrary for Index[src]

type Parameters = ()

The type of parameters that [arbitrary_with] accepts for configuration of the generated [Strategy]. Parameters must implement [Default]. Read more

type Strategy = IndexStrategy

The type of [Strategy] used to generate values of type Self. Read more

fn arbitrary() -> Self::Strategy[src]

Generates a [Strategy] for producing arbitrary values of type the implementing type (Self). Read more

impl Debug for Index[src]

impl Copy for Index[src]

impl Clone for Index[src]

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

Performs copy-assignment from source. Read more

Auto Trait Implementations

impl Send for Index

impl Sync for Index

Blanket Implementations

impl<T> From for T[src]

impl<T, U> TryFrom for T where
    U: Into<T>, 

type Error = Infallible

The type returned in the event of a conversion error.

impl<T, U> TryInto for T where
    U: TryFrom<T>, 

type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.

impl<T, U> Into for T where
    U: From<T>, 

impl<T> Borrow for T where
    T: ?Sized

impl<T> BorrowMut for T where
    T: ?Sized

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

impl<T> ToOwned for T where
    T: Clone

type Owned = T

The resulting type after obtaining ownership.