!CHAPTER LET 

The *LET* statement can be used to assign an arbitrary value to a variable.  The
variable is then introduced in the scope the *LET* statement is placed in.  The
general syntax is:

```
LET variable-name = expression
```

*LET* statements are mostly used to declare complex computations and to avoid
repeated computations of the same value at multiple parts of a query.

```
FOR u IN users
  LET numRecommendations = LENGTH(u.recommendations)
  RETURN { 
    "user" : u, 
    "numRecommendations" : numRecommendations, 
    "isPowerUser" : numRecommendations >= 10 
  } 
```

In the above example, the computation of the number of recommendations is
factored out using a *LET* statement, thus avoiding computing the value twice in
the *RETURN* statement.

Another use case for *LET* is to declare a complex computation in a subquery,
making the whole query more readable.

```
FOR u IN users
  LET friends = (
  FOR f IN friends 
    FILTER u.id == f.userId
    RETURN f
  )
  LET memberships = (
  FOR m IN memberships
    FILTER u.id == m.userId
      RETURN m
  )
  RETURN { 
    "user" : u, 
    "friends" : friends, 
    "numFriends" : LENGTH(friends), 
    "memberShips" : memberships 
  }
```