MongoDB $exp Operator

MongoDB provides different types of arithmetic expression operators that are used in the aggregation pipeline stages $exp operator is one of them. This operator is used to raise Euler’s number (i.e. e ) to the specified exponent and returns the result.

Syntax: 

{ $exp: <exponent> }

Here, the exponent is a valid expression until it resolves to a number. 

• If the entered value resolves to null, then this operator will return null.
• If the entered value resolves to NaN, then this operator will return NaN.
• If the entered value refers to a missing field, then this operator will return null.

Examples:

In the following examples, we are working with:

Database: GeeksforGeeks

Collection: example

Document: two documents that contain the details of the shapes in the form of field-value pairs.

Using $exp Operator:

In this example, we are going to find the exponent of the value of the side field.

db.example.aggregate([ {$match: {name: "Square"}},
... {$project: {result: {$exp: "$side"}}}])

Using $exp Operator in the Embedded Document:

In this example, we are going to find the exponent of the difference of the values of measurement.height and measurement.width fields.

db.example.aggregate([ {$match: {name: "Rectangle"}},
... {$project: {result: {$exp:
... {$subtract: ["$measurement.height", "$measurement.width"]}}}}])