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# Operators

An operator is a statement that evaluates some code, and makes a decision about what to do next. Operators can be used for comparing two values, inspecting a single value, or evaluating whether or not some code returns `true`.
For further discussion on how Liquid treats values, see their documentation: Truthiness and falsiness in Liquid.

## Comparison operators

If `b = 6`, the table below illustrates the comparison operators and the way they interact with `b`:
 Operator Description Example Result `==` equal to `b == 6` `true` `!=` not equal `b != 6` `false` `>` greater than `b > 5` `true` `<` less than `b < 6` `false` `>=` greater than or equal to `b >= 6` `true` `<=` less than or equal to `b <= 6` `true`

### Examples

{% assign order_qualifies = false %}
{% if order.cancelled_at == blank and cancel_risk %}
{% assign order_qualifies = true %}
{% endif %}
{% if has_product != true %}
{% log "Order has no products; skipping" %}
{% assign send_email = false %}
{% endif %}

### Testing for blank, empty

Liquid supports equality/inequality testing a value against `blank` or `empty`. In this way, Liquid allows the author to ask, "is this value blank?", or "is this value empty?"

#### Blank

Quoting from the Rails API:
An object is blank if it's false, empty, or a whitespace string. For example, `nil`, '', ' ', [], {}, and `false` are all blank.
{% assign empty_string = "" %}
{% assign whitespace_string = " " %}
{% assign non_blank_string = " !! " %}
{% assign non_empty_array = "1,2,3" | split: "," %}
{% assign empty_hash = hash %}
{% comment %}
The following `if` statements all pass.
{% endcomment %}
{% if empty_string == blank %}
{% if whitespace_string == blank %}
{% if non_blank_string != blank %}
{% if non_empty_array != blank %}
{% if empty_hash == blank %}

#### Empty

An array, hash, or string can be tested for emptiness. An array is empty if it has no elements; a hash is empty if it has no key-value pairs; a string is empty if its length is zero.
A string that only contains whitespace is not empty, but it is blank!
{% assign empty_string = "" %}
{% assign whitespace_string = " " %}
{% assign non_blank_string = " !! " %}
{% assign non_empty_array = "1,2,3" | split: "," %}
{% assign empty_hash = hash %}
{% comment %}
The following `if` statements all pass.
{% endcomment %}
{% if empty_string == empty %}
{% if whitespace_string != empty %}
{% if non_blank_string != empty %}
{% if non_empty_array != empty %}
{% if empty_hash == empty %}

## Contains operator

The `contains` operator is used to check for the existence of a substring in a string, or for a specific element in an array.

### Substring containment

{% if email_domain contains "@" %}
{% error "Do not include '@' symbols in email domains. Thanks!" %}
{% endif %}

### Array element containment

{% assign product_tags = "foo, bar, baz" | split: ", " %}
{% assign product_is_tagged_bar = false %}
{% if product_tags contains "bar" %}
{% assign product_is_tagged_bar = true %}
{% endif %}

## Logical operators

Liquid has two logical operators: `and` and `or`.
If `b = 3` and `c = 6`, the table below illustrates the logical operators in Liquid, and the way they interact with `b` and `b`:
 Operator Example Result `and` `b < 2 and c < 6` `false` `or` `b < 2 or c < 6` `true`