iterator.md

Js-sdsl overloads the [Symbol.iterator] function for all iterable containers for the for...of syntax.

In addition to this, we provide C++ STL-like bidirectional iterators for sequential containers and tree containers.

Symbol.iterator

Explanation of iterators on MDN

Take Vector as an example:

const v = new Vector([1, 2, 3]);
for (const u of v) {
    console.log(u);     // 1, 2, 3
}

Bidirectional Iterator

Like C++, we provide forward (normal) / reverse (reverse) iterator modes, and provide four functions begin, end, rBegin, rEnd for containers that support iterators.

Since there is no concept of pointers in Js, Js-sdsl simulates * operations by adding pointer attributes to iterators, and next and pre functions to simulate ++ and -- operations.

Note that pre and next will change the original pointer position in the object, just like ++it in C++, it itself will also be changed.

import type { IteratorType } from 'js-sdsl';

const v = new Vector([1, 2, 3]);
let it = v.begin();
console.log(it.pointer);        // 1
console.log(
    it.iteratorType ===
    IteratorType.NORMAL
);                              // true
it = it.next();
console.log(it.pointer);        // 2
it = it.pre();
console.log(it.pointer);        // 1

for (
    let i = v.begin(); 
    !i.equals(v.end()); 
    i = i.next()
) {
    console.log(i.pointer);     // 1, 2, 3
}

it = v.rBegin();
console.log(it.pointer);        // 3
console.log(
    it.iteratorType === 
    IteratorType.REVERSE
);                              // true
it = it.next();
console.log(it.pointer);        // 2
it = it.pre();
console.log(it.pointer);        // 3

Note, as in C++, if you delete the element pointed to by the iterator, the iterator will be invalidated, which is a dangerous operation.

If you want to save an iterator before move it, you can use copy.

const v = new Vector([1, 2, 3]);
let it = v.begin();
const itCopy = it.copy();
it = it.next();
console.log(it.pointer);        // 2
console.log(itCopy.pointer);    // 1

Try it

<textarea id='input'> const v = new Vector([1, 2, 3]); let it = v.begin(); const itCopy = it.copy(); it = it.next(); console.log(it.pointer); // 2 console.log(itCopy.pointer); // 1 </textarea>

Run it Reset