# Use functions in formula expressions
<a name="expression-functions"></a>

You can use the following functions to operate on data in your formula expressions.

Transforms and metrics support different functions. The following table indicates which types of functions are compatible with each type of formula property.

**Note**  
You can include a maximum of 10 functions in a formula expression.


| Function type | Transforms | Metrics | 
| --- | --- | --- | 
|  [Use common functions in formula expressions](expression-common-functions.md)  |  <a name="polaris-yes-para"></a>![\[A green circle with a checkmark for yes.\]](http://docs.amazonaws.cn/en_us/iot-sitewise/latest/userguide/images/icon-yes.png) Yes  |  <a name="polaris-yes-para"></a>![\[A green circle with a checkmark for yes.\]](http://docs.amazonaws.cn/en_us/iot-sitewise/latest/userguide/images/icon-yes.png) Yes  | 
|  [Use comparison functions in formula expressions](expression-comparison-functions.md)  |  <a name="polaris-yes-para"></a>![\[A green circle with a checkmark for yes.\]](http://docs.amazonaws.cn/en_us/iot-sitewise/latest/userguide/images/icon-yes.png) Yes  |  <a name="polaris-yes-para"></a>![\[A green circle with a checkmark for yes.\]](http://docs.amazonaws.cn/en_us/iot-sitewise/latest/userguide/images/icon-yes.png) Yes  | 
|  [Use conditional functions in formula expressions](expression-conditional-functions.md)  |  <a name="polaris-yes-para"></a>![\[A green circle with a checkmark for yes.\]](http://docs.amazonaws.cn/en_us/iot-sitewise/latest/userguide/images/icon-yes.png) Yes  |  <a name="polaris-yes-para"></a>![\[A green circle with a checkmark for yes.\]](http://docs.amazonaws.cn/en_us/iot-sitewise/latest/userguide/images/icon-yes.png) Yes  | 
|  [Use string functions in formula expressions](expression-string-functions.md)  |  <a name="polaris-yes-para"></a>![\[A green circle with a checkmark for yes.\]](http://docs.amazonaws.cn/en_us/iot-sitewise/latest/userguide/images/icon-yes.png) Yes  |  <a name="polaris-yes-para"></a>![\[A green circle with a checkmark for yes.\]](http://docs.amazonaws.cn/en_us/iot-sitewise/latest/userguide/images/icon-yes.png) Yes  | 
|  [Use aggregation functions in formula expressions](expression-aggregation-functions.md)  |  <a name="polaris-no-para"></a>![\[A red circle with the letter x for no.\]](http://docs.amazonaws.cn/en_us/iot-sitewise/latest/userguide/images/icon-no.png) No  |  <a name="polaris-yes-para"></a>![\[A green circle with a checkmark for yes.\]](http://docs.amazonaws.cn/en_us/iot-sitewise/latest/userguide/images/icon-yes.png) Yes  | 
|  [Use temporal functions in formula expressions](expression-temporal-functions.md)  |  <a name="polaris-yes-para"></a>![\[A green circle with a checkmark for yes.\]](http://docs.amazonaws.cn/en_us/iot-sitewise/latest/userguide/images/icon-yes.png) Yes  |  <a name="polaris-yes-para"></a>![\[A green circle with a checkmark for yes.\]](http://docs.amazonaws.cn/en_us/iot-sitewise/latest/userguide/images/icon-yes.png) Yes  | 
|  [Use date and time functions in formula expressions](expression-date-and-time-functions.md)  |  <a name="polaris-yes-para"></a>![\[A green circle with a checkmark for yes.\]](http://docs.amazonaws.cn/en_us/iot-sitewise/latest/userguide/images/icon-yes.png) Yes  |  <a name="polaris-yes-para"></a>![\[A green circle with a checkmark for yes.\]](http://docs.amazonaws.cn/en_us/iot-sitewise/latest/userguide/images/icon-yes.png) Yes  | 

## Function syntax
<a name="expression-function-syntax"></a>

You can use the following syntax to create functions:

Regular syntax  
With the regular syntax, the function name is followed by parentheses with zero or more arguments.  
`function_name(argument1, argument2, argument3, ...)`. For example, functions with the regular syntax might look like `log(x)` and `contains(s, substring)`.

Uniform function call syntax (UFCS)  
UFCS enables you to call functions using the syntax for method calls in object-oriented programming. With UFCS, the first argument is followed by dot (`.`), then the function name and the remaining arguments (if any) inside parentheses.  
`argument1.function_name(argument2, argument3, ...)`. For example, functions with UFCS might look like `x.log()` and `s.contains(substring)`.  
You can also use UFCS to chain subsequent functions. Amazon IoT SiteWise uses the evaluation result of the current function as the first argument for the next function.  
For example, you can use `message.jp('$.status').lower().contains('fail')` instead of `contains(lower(jp(message, '$.status')),'fail')`.  
For more information, visit the [D Programming Language](https://tour.dlang.org/tour/en/gems/uniform-function-call-syntax-ufcs) website.

**Note**  
You can use UFCS for all Amazon IoT SiteWise functions.  
Amazon IoT SiteWise functions are not case sensitive. For example, you can use `lower(s)` and `Lower(s)` interchangeably.