The IDL language is dynamically typed. This means that an operation on a variable can change that variable’s type. In general, when variables of different types are combined in an expression, the result has the data type that yields the highest precision. For example, if an integer variable is added to a floating-point variable, the result will be a floating-point variable. See Data Type and Structure of Expressions.
Tip: Use the SIZE function to determine the data type of an IDL variable or expression.