Iterator

The iterator that is returned when calling values on a generator.

Here we will use the integer generator as an example:

const { integer } = require("chance-generators")

API

isExpandable

Is true if the iterator can be expanded.

isShrinkable

Is true if the iterator can be shrunken.

expand(value)

Expands the current generator around the given value while still honoring the constraints of the original generator. The given value should be the last value the generator has produced.

You can use this method when a generator produces an interesting input and you want to search around that value.

const iterator = integer({ min: -10000, max: 10000 }).values();

iterator.expand(100);

expect(iterator.take(10), "to equal", [100, 9015, 100, 5594, 119, 100, 31, 100, 100, 174]);

As you can see the expanded iterator will produce values around 100 as that is our expansion value.

next()

Produces a new value based on the generator that this iterator was created from.

const integerIterator = integer.values();

expect([integerIterator.next(), integerIterator.next(), integerIterator.next()], "to equal", [

-2260084377780223,

5342043492581377,

8119347222413313

]);

shrink(value)

Returns a new generator that is shunken around the given value while still honoring the constraints of the original generator.

integerIterator.shrink(1000);

This will shrink the iterator to produce values between 0 and 1000.

expect(integerIterator.take(5), "to equal", [183, 732, 780, 599, 597]);

If we shrink the iterator again with the smallest produces value from the last run. It will produce values been 0 and 183.

integerIterator.shrink(183);

expect(integerIterator.take(5), "to equal", [28, 82, 28, 18, 10]);

The idea is that every time you find interesting input, you can try to search for a smaller input by shrinking the iterator.

take(n)

Produces n items with the generator and return them as an array:

expect(integer.values().take(3), "to equal", [

-2260084377780223,

5342043492581377,

8119347222413313

]);