### 3 unstable releases

0.2.0 | Jan 18, 2021 |
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0.1.1 | Jan 14, 2021 |

0.1.0 | Jan 14, 2021 |

#**1468** in Algorithms

**MIT**license

7KB

94 lines

# unfold

A simple unfold implementation in Rust

unfold let you create an iterator that, staring from a given initial value, applies a given function to the current state, store the result for the next iteration, and return the current state.

Unfold defines an endless iterator: you must stop it *by hand*, like in the
example.

## Example

`use` `unfold``::`Unfold`;`
`//` Create a vector containing the first 5 numbers from the Fibonacci
`//` series
`let` fibonacci_numbers`:` `Vec``<``u64``>` `=` `Unfold``::`new`(``|``(``a``,` `b``)``|` `(`b`,` a `+` b`)``,` `(``0``,` `1``)``)`
`.``map``(``|``(``a``,` _`)``|` `a``)`
`.``take``(``5``)` `//`Unfold iterator never stops.
`.``collect``(``)``;`
`assert_eq!``(``vec!``[``0``,` `1``,` `1``,` `2``,` `3``]``,` fibonacci_numbers`)``;`

###
`lib.rs`

:

# unfold

The unfold
function takes as input a function *f* and an initial *i* value and returns
a list defined as
[i, f(i), f(f(i)), ...].

This library defines

a struct
that implements the unfold function as an `Unfold`*endless*
iterator.

## Quick Start

To use

is quite simple. The user calls
the new function providing a function as first argument
and the initial value as second argument.
An `Unfold`

instance can be then used as any iterator,
but don't forget: Unfold never ends, it must be stopped.`Unfold`

Here an example:

`use` `unfold``::`Unfold`;`
`//` Create a vector containing the first 5 numbers from the Fibonacci
`//` series
`let` fibonacci_numbers`:` `Vec``<``u64``>` `=` `Unfold``::`new`(``|``(``a``,` `b``)``|` `(`b`,` a `+` b`)``,` `(``0``,` `1``)``)`
`.``map``(``|``(``a``,` _`)``|` `a``)`
`.``take``(``5``)` `//`Unfold iterator never stops.
`.``collect``(``)``;`
`assert_eq!``(``vec!``[``0``,` `1``,` `1``,` `2``,` `3``]``,` fibonacci_numbers`)``;`