The STRLEN function returns the length of its string-type argument. If the argument is not a string, it is first converted to string type.
The expression for which the string length is desired. If this parameter is not a string, it is converted using IDL's default formatting rules in order to determine the length. The result is a long integer. If Expression is an array, the result is a long integer array with the same structure, where each element contains the length of the corresponding Expression element.