The Function question type uses its text field to perform 'internal' calculations that are imperceptible to the interviewer, but calculations that can, nevertheless, influence data collection and survey logic.

• Functions can use symbols, arithmetic operations, and/or Boolean operators to perform calculations and evaluate branching conditions; and
• They can use specific functional commandsto carry out operations and branching conditions.

Depending on the function and syntax specified in the CAPIDesigner, a value is returned by the WebSurvey as a response to each question that indicates success, failure, or problem in the execution of the function. Sample response values for each function are listed at the bottom of the Possible uses table for each function in the CAPI help documentation. The only response values returned by the WebSurvey are:

1	=	Success
0	=	Failure
-999999999	=	Problem, i.e., Error executing the function.

Troubleshooting Functions (a.k.a. Runtime Errors)

When troubleshooting a function for runtime errors, pay close attention to the return values of each function. The "Problem" in executing the function depends 100% on the function that produced the error. It is in combination with the error value returned and the function used where the archivist/designer needs to begin the troubleshooting process:

• Examine the error code returned with the documentation of the function used;
• Check the syntax of the function;
• Get the definition of the function from the functional command document. At the bottom of the "Possible uses" table displayed for each function, there are specific examples of what might be associated with the -99999999 errors for that function. Look in the "Error report" column for the possible meanings; and
• Check the data in the debugger and go from that question up by looking for the variables that are used in the function.

Note: The results of a functional command specified in the Functions question type should not be confused with the question's response ( = return values). The results are a consequence of the operation or calculation carried out by the logic of the function. If a result is needed later in the survey, it will need to be saved as a Symbol (see, Save Symbol field) for later reference. Results may include the creation of a calendar, file, roster, etc.; or they may be a cleaned string of characters, a converted or repaired date, or the initiation and termination of a loop.

Special Characters

In the Functions question type two sets of characters have special significance:

• { } Curly brackets are used in pairs to denote that the characters enclosed within are symbols associated with some variable collected elsewhere in the survey by the Save Symbol field.
• [ ] are used to enclose question names. Names thus enclosed have values that were collected a responses to these questions.
• {^ ^} Curly brackets with carets, ^, are used in pairs to denote that the characters enclosed within are array elements associated with some variable collected elsewhere in the survey by the Save Symbol field.
• {* *} Curly brackets with asterisks, *, are used in pairs to denote that the characters enclosed within are roster or roster elements associated with some variable collected elsewhere in the survey by the Save Symbol field.

Sample Functions question type shown in the CAPIDesigner: