An execution branch attached to a function is called a "receiver" as it has the special behavior that the terms of any returned axiom can be directly accessed in the branch. This has the effect that, just as a function can be passed parameters when called, it can return parameters on completion. This feature works well with the select operation, as the returned parameters are conveniently named in the declaration header. If a function returns a type other than an axiom, then the return value is accessed using a variable with the same name as the function.

Format

The receiver format consists of the following four components:

flow identifier( parameters ) { flow-body }

The identifier will be a one or two part name depending on where the function being called is located. For a select operation, the first parameter provides the key and cannot be omitted. Additional call parameters in a select operation can set default values of one or more select parameters named in the declaration header..

The following examples demonstrate the receiver format for a variety of function return types starting with axiom.

Select Axiom

stamp-duty2.taq changes the original by attaching a receiver to the "sale_bracket" select function. The receiver performs a calculation using variables with names matching "threshold", "base" and "percent" in the sale_bracket declaration header. These variables are set from the corresponding terms of the selection axiom. Here is the "stamp_duty_payable" flow

Note one particular behavior of a select function is that the receiver evaluation is skipped if there is no match. Therefore the original branch on success strategy is preserved for when the sale amount is above $5,000.