Cross platform custom functions

A system for support custom functions within an application, the system comprising:

• one or more electronic processors configured to:
• receive an application add-in comprising a custom function and a custom function source location, the application and the custom function available across a plurality of platforms;
• register, within the application, the custom function using the custom function source location;
• receive a request to invoke the custom function within a first document within the application on a first platform:
• download a custom function implementation from the custom function location,
• execute the custom function implementation;
• and
• receive a first return value from the custom function implementation.

A computer-readable storage media storing computer-executable instructions for program synthesis for a query, the stored instructions comprising:

• instructions to receive an application add-in comprising a custom function and a custom function source location, the application and the custom function available across a plurality of platforms;
• instructions to register, within the application, the custom function using the custom function source location;
• instructions to receive a request to invoke the custom function within a first document within the application on a first platform;
• instructions to download a custom function implementation from the custom function location;
• instructions to execute the custom function implementation;
• and instructions to receive a first return value from the custom function implementation.