Declare a function

Defining a function is not in itself enough to make something appropriate happen at the time the integration engine server processes the function call. So far all you have done is to indicate that a function named IsLeapYear can be called along with requirements, from your expressions.

When the integration engine performs a function call, it first evaluates the values of the real parameters, then suspends the evaluation of the DML Block expression and hands over processing control to the called Custom Function itself. The following diagram illustrates the processing sequence:

Function call processing sequence

When the Custom Function completes processing and returns a value, this value is used to continue the evaluation in the expression from which the call was made. The red section of the preceding graphic represents the Custom Function code block that supplies the service, this block is called the implementation (or body) of the function.

Declaring a function is the process of writing the implementation of the function. Implementations of Custom Functions are not DML expressions: to write such bodies you need a real programming language and possibly extra libraries. Most of the time declaring a Custom Function is accomplished using third party tools.

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