Sedona XPRESSion Evaluator Reference Guide

Define Function VI

Establishes a user-defined function for use in other function definitions and expressions.

This VI is very useful for building sophisticated function libraries. The function can be any BNF expression containing any built-in function OR another user-defined function. The order in which multiple calls to Define Function are executed is unimportant, even if the function definitions are interrelated. If the function is referenced by other previously-defined functions, then all of those "parent" functions are updated to reflect the new form of function. Similarly, if function references other user-defined functions (which may or may not have been defined yet), then it will be updated when any of its "child" functions are (re)defined.

	error in (no error) describes any error conditions prior to this VIs execution.
	function descriptor function descriptor is a string describing the form of a user-defined function. The syntax for function descriptor is: FuncName(a,b,c...z) = <expr> where a,b,c ... are dummy variables and can be any convenient set of variable names, and <expr> is any Backus-Naur expression containing only the dummy variables a,b,c... as identifiers. The function descriptor may also contain references to other user-defined functions (and, of course, to any built-in functions). The following are all valid function descriptors: MyFunc(a,b,c) = a * b ^ c * OurFunc(a*b,log(c),1.3E-4) YourFunc(x,y) = (x ^ (2 * y)) * MyFunc(x,x^2,x^3) OurFunc(one,two,three) = one + two + sin(three)
	initialize (F) specifies whether or not to initialize the internal database of user-defined functions. If TRUE, then all user-defined functions currently loaded in memory will be deleted. If FALSE, then the function described in function descriptor is appended to the internal database of user-defined functions.
	error out contains error information. If the error in cluster indicated an error, the error out cluster contains the same information. Otherwise, error out describes this VIs error status.
	index out
	user func