# Bag

A bag (also known as a multi-set) is a unordered collection of objects, similar to a hash table, where each object has a count number, which represents the number of times it exists in the bag.

```ruby
Bag('foo', 'bar', 'baz')
```

## Operations

The Bag class supports all the set operators, such as intersection, difference, symmetric difference, union and concatenation.

```ruby
var A = Bag('foo', 'bar', 'baz', 'foo')
var B = Bag('bar', 'foo', 'qux')

# Count how many times is 'foo' present in the bag A
say A.count('foo')  #=> 2

# Intersection
say (A & B)         #=> Bag("foo", "bar")

# Union
say (A | B)         #=> Bag("qux", "bar", "baz", "foo", "foo")

# Difference
say (A - B)         #=> Bag("baz", "foo")
say (B - A)         #=> Bag("qux")

# Symmetric difference
say (A ^ B)         #=> Bag("foo", "qux", "baz")

# Concatenation
say (A + B)         #=> Bag("foo", "foo", "foo", "bar", "bar", "baz", "qux")
```

## Updating the bag

The methods `bag.add_pair(obj, count)` and `bag.update_pair(obj, count)` can be used for efficiently updating a bag in-place.

```ruby
var A = Bag('foo', 'foo', 'bar')

# Add 'bar' with count=2
A.add_pair('baz', 2)

say A   #=> Bag("baz", "baz", "bar", "foo", "foo")

# Update the count of 'foo'
A.update_pair('foo', 1)

say A   #=> Bag("baz", "baz", "bar", "foo")
```

Furthermore, the method `bag.delete(obj)` can be used for removing one occurrence of object `obj` from the bag, while the `.delete_all(obj)` can be used for removing all the occurrences of `obj` from the bag.


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://trizen.gitbook.io/sidef-lang/syntax_and_semantics/literals/bag.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.