> ## Documentation Index > Fetch the complete documentation index at: https://axiom-mano-sample-app.mintlify.site/llms.txt > Use this file to discover all available pages before exploring further. # Conversion functions > Learn how to use and combine different conversion functions in APL ## Conversion functions | **Function Name** | **Description** | | --------------------------------------------- | ------------------------------------------------------------------------------------------ | | [ensure\_field()](#ensure-field) | Ensures the existence of a field and returns its value or a typed nil if it doesn’t exist. | | [tobool()](#tobool) | Converts input to boolean (signed 8-bit) representation. | | [todatetime()](#todatetime) | Converts input to datetime scalar. | | [todouble(), toreal()](#todouble\(\),-toreal) | Converts the input to a value of type `real`. `todouble()` and `toreal()` are synonyms. | | [tostring()](#tostring) | Converts input to a string representation. | | [totimespan()](#totimespan) | Converts input to timespan scalar. | | [tohex()](#tohex) | Converts input to a hexadecimal string. | | [tolong()](#tolong) | Converts input to long (signed 64-bit) number representation. | | [dynamic\_to\_json()](#dynamic-to-json) | Converts a scalar value of type dynamic to a canonical string representation. | | [isbool()](#isbool) | Returns a value of true or false if the expression value is passed. | | [toint()](#toint) | Converts the input to an integer value (signed 64-bit) number representation. | ## ensure\_field() Ensures the existence of a field and returns its value or a typed nil if it doesn’t exist. ### Arguments | **name** | **type** | **description** | | ----------- | -------- | ------------------------------------------------------------------------------------------------------ | | field\_name | string | The name of the field to ensure exists. | | field\_type | type | The type of the field. See [scalar data types](/apl/data-types/scalar-data-types) for supported types. | ### Returns This function returns the value of the specified field if it exists, otherwise it returns a typed nil. ### Examples ```kusto ensure_field(field_name, field_type) ``` ### Handle missing fields In this example, the value of `show_field` is nil because the `myfield` field doesn’t exist. ```kusto ['sample-http-logs'] | extend show_field = ensure_field("myfield", typeof(string)) ``` [Run in Playground](https://play.axiom.co/axiom-play-qf1k/query?initForm=%7B%22apl%22%3A%20%22%5B%27sample-http-logs%27%5D%5Cn%7C%20extend%20show_field%20%3D%20ensure_field%28%27myfield%27%2C%20typeof%28string%29%29%22%7D) ### Access existing fields In this example, the value of `newstatus` is the value of `status` because the `status` field exists. ```kusto ['sample-http-logs'] | extend newstatus = ensure_field("status", typeof(string)) ``` [Run in Playground](https://play.axiom.co/axiom-play-qf1k/query?initForm=%7B%22apl%22%3A%20%22%5B%27sample-http-logs%27%5D%5Cn%7C%20extend%20newstatus%20%3D%20ensure_field%28%27status%27%2C%20typeof%28string%29%29%22%7D) ### Future-proof queries In this example, the query is prepared for a field named `upcoming_field` that is expected to be added to the data soon. By using `ensure_field()`, logic can be written around this future field, and the query will work when the field becomes available. ```kusto ['sample-http-logs'] | extend new_field = ensure_field("upcoming_field", typeof(int)) | where new_field > 100 ``` ## tobool() Converts input to boolean (signed 8-bit) representation. ### Arguments * Expr: Expression that will be converted to boolean. ### Returns * If conversion is successful, result will be a boolean. If conversion isn’t successful, result will be `false` ### Examples ```kusto tobool(Expr) toboolean(Expr) (alias) ``` ```kusto tobool("true") == true ``` [Run in Playground](https://play.axiom.co/axiom-play-qf1k/query?initForm=%7B%22apl%22%3A%22%5B%27sample-http-logs%27%5D%5Cn%7C%20project%20conversion_function%20%3D%20tobool%28%5C%22true%5C%22%29%20%3D%3D%20true%22%2C%22queryOptions%22%3A%7B%22quickRange%22%3A%2230d%22%7D%7D) * Result: ```json { "conversion_function": true } ``` ## todatetime() Converts input to datetime scalar. ### Arguments * Expr: Expression that will be converted to datetime. ### Returns If the conversion is successful, the result will be a datetime value. Else, the result will be `false.` ### Examples ```kusto todatetime(Expr) ``` ```kusto todatetime("2022-11-13") ``` [Run in Playground](https://play.axiom.co/axiom-play-qf1k/query?initForm=%7B%22apl%22%3A%22%5B%27sample-http-logs%27%5D%5Cn%7C%20project%20conversion_function%20%3D%20todatetime%28%5C%222022-11-13%5C%22%29%22%2C%22queryOptions%22%3A%7B%22quickRange%22%3A%2230d%22%7D%7D) * Result ```json { "boo": "2022-11-13T00:00:00Z" } ``` ## todouble(), toreal() Converts the input to a value of type real. **(todouble() is an alternative word to toreal())** ### Arguments * Expr: An expression whose value will be converted to a value of type `real.` ### Returns If conversion is successful, the result is a value of type real. If conversion is not successful, the result returns false. ### Examples ```kusto toreal(Expr)todouble(Expr) ``` ```kusto toreal("1567") == 1567 ``` [Run in Playground](https://play.axiom.co/axiom-play-qf1k/query?initForm=%7B%22apl%22%3A%22%5B%27sample-http-logs%27%5D%5Cn%7C%20project%20conversion_function%20%3D%20toreal%28%5C%221567%5C%22%29%20%3D%3D%201567%22%2C%22queryOptions%22%3A%7B%22quickRange%22%3A%2230d%22%7D%7D) * Result: ```json { "conversion_function": true } ``` ## tostring() Converts input to a string representation. ### Arguments * `Expr:` Expression that will be converted to string. ### Returns If the Expression value is non-null, the result will be a string representation of the Expression. If the Expression value is null, the result will be an empty string. ### Examples ```kusto tostring(Expr) ``` ```kusto tostring(axiom) == "axiom" ``` [Run in Playground](https://play.axiom.co/axiom-play-qf1k/query?initForm=%7B%22apl%22%3A%22%5B%27sample-http-logs%27%5D%5Cn%7C%20project%20conversion_function%20%3D%20tostring%28%5C%22axiom%5C%22%29%22%2C%22queryOptions%22%3A%7B%22quickRange%22%3A%2230d%22%7D%7D) * Result: ```json { "conversion_function": "axiom" } ``` ## totimespan Converts input to timespan scalar. ### Arguments * `Expr:` Expression that will be converted to timespan. ### Returns If conversion is successful, result will be a timespan value. Else, result will be false. ### Examples ```kusto totimespan(Expr) ``` [Run in Playground](https://play.axiom.co/axiom-play-qf1k/query?initForm=%7B%22apl%22%3A%22%5B%27sample-http-logs%27%5D%5Cn%7C%20project%20conversion_function%20%3D%20totimespan%282022-11-13%29%22%2C%22queryOptions%22%3A%7B%22quickRange%22%3A%2230d%22%7D%7D) * Result ```json { "conversion_function": "1.998µs" } ``` ## tohex() Converts input to a hexadecimal string. ### Arguments * Expr: int or long value that will be converted to a hex string. Other types are not supported. ### Returns If conversion is successful, result will be a string value. If conversion is not successful, result will be false. ### Examples ```kusto tohex(value) ``` ```kusto tohex(-546) == 'fffffffffffffdde' ``` ```kusto tohex(546) == '222' ``` [Run in Playground](https://play.axiom.co/axiom-play-qf1k/query?initForm=%7B%22apl%22%3A%22%5B%27sample-http-logs%27%5D%5Cn%7C%20project%20conversion_function%20%3D%20tohex%28-546%29%22%2C%22queryOptions%22%3A%7B%22quickRange%22%3A%2230d%22%7D%7D) * Result: ```json { "conversion_function": "fffffffffffffdde" } ``` ## tolong() Converts input to long (signed 64-bit) number representation. ### Arguments * Expr: Expression that will be converted to long. ### Returns If conversion is successful, result will be a long number. If conversion is not successful, result will be false. ### Examples ```kusto tolong(Expr) ``` ```kusto tolong("241") == 241 ``` [Run in Playground](https://play.axiom.co/axiom-play-qf1k/query?initForm=%7B%22apl%22%3A%22%5B%27sample-http-logs%27%5D%5Cn%7C%20project%20conversion_function%20%3D%20tolong%28%5C%22241%5C%22%29%22%2C%22queryOptions%22%3A%7B%22quickRange%22%3A%2230d%22%7D%7D) * Result: ```json { "conversion_function": 241 } ``` ## dynamic\_to\_json() Converts a scalar value of type `dynamic` to a canonical `string` representation. ### Arguments * dynamic input (EXpr): The function accepts one argument. ### Returns Returns a canonical representation of the input as a value of type `string`, according to the following rules: * If the input is a scalar value of type other than `dynamic`, the output is the app of `tostring()` to that value. * If the input in an array of values, the output is composed of the characters **\[, ,, and ]** interspersed with the canonical representation described here of each array element. * If the input is a property bag, the output is composed of the characters **\{, ,, and }** interspersed with the colon (:)-delimited name/value pairs of the properties. The pairs are sorted by the names, and the values are in the canonical representation described here of each array element. ### Examples ```kusto dynamic_to_json(dynamic) ``` ```kusto ['sample-http-logs'] | project conversion_function = dynamic_to_json(dynamic([1,2,3])) ``` [Run in Playground](https://play.axiom.co/axiom-play-qf1k/query?initForm=%7B%22apl%22%3A%22%5B%27sample-http-logs%27%5D%5Cn%7C%20project%20conversion_function%20%3D%20dynamic_to_json%28dynamic%28%5B1%2C2%2C3%5D%29%29%22%2C%22queryOptions%22%3A%7B%22quickRange%22%3A%2230d%22%7D%7D) * Result: ```json { "conversion_function": "[1,2,3]" } ``` ## isbool() Returns a value of true or false if the expression value is passed. ### Arguments * Expr: The function accepts one argument. The variable of expression to be evaluated. ### Returns Returns `true` if expression value is a bool, `false` otherwise. ### Examples ```kusto isbool(expression) ``` ```kusto isbool("pow") == false ``` [Run in Playground](https://play.axiom.co/axiom-play-qf1k/query?initForm=%7B%22apl%22%3A%22%5B%27sample-http-logs%27%5D%5Cn%7C%20project%20conversion_function%20%3D%20isbool%28%5C%22pow%5C%22%29%22%2C%22queryOptions%22%3A%7B%22quickRange%22%3A%2230d%22%7D%7D) * Result: ```json { "conversion_function": false } ``` *** ## toint() Converts the input to an integer value (signed 64-bit) number representation. ### Arguments * Value: The value to convert to an [integer](/apl/data-types/scalar-data-types#the-int-data-type). ### Returns If the conversion is successful, the result will be an integer. Otherwise, the result will be `null`. ### Examples ```kusto toint(value) ``` ```kusto | project toint("456") == 456 ``` [Run in Playground](https://play.axiom.co/axiom-play-qf1k/query?initForm=%7B%22apl%22%3A%20%22%5B%27sample-http-logs%27%5D%5Cn%7C%20project%20toint%28%5C%22456%5C%22%29%20%3D%3D%20456%22%7D)