# PDL_GetParamDouble

## Description

Extracts a named `double` parameter passed to a service callback function. You can register a callback function with a service using the PDL_ServiceCallWithCallback API. All parameters are passed as strings, though their underlying types (double, int, or string) can be different.

This API returns `0.0` if the parameter is not found. You can use the PDL_ParamExists API to check if the parameter exists before calling this API.

See Accessing Services for more information and examples.

## Syntax

>     double PDL_GetParamDouble(PDL_ServiceParameters *params, const char *name);

Argument | Description
--- | ---
params | Parameters from which to extract data. This is passed to the callback function from the service and you simply pass it on here without modification.
name | Name of the argument to extract.

## Returns

>     passed parameter, or `0.0` if the parameter does not exist.

See also:

- PDL_ServiceCall
- PDL_ServiceCallWithCallback
- PDL_UnregisterServiceCallback
- PDL_GetParamInt
- PDL_GetParamString
- PDL_ParamExists