The purpose of this chapter is to illustrate the use of values of basic types: numbers, characters, truth values and strings by means of some examples. The concepts of operator overloading and type inference are explained. Furthermore, the chapter contains a gentle introduction to higher-order functions. It is explained how to declare operators, and the concepts of equality and ordering in F# are introduced. After reading the chapter the reader should be able to construct simple programs using numbers, characters, strings and truth values.

Numbers. Truth values. The unit type

From mathematics we know the set of natural numbers as a subset of the set of integers, which again is a subset of the rational numbers (i.e., fractions), and so on. In F#, however, the set of values with the type: int, for the integers, is considered to be disjoint from the set of values with the type: float, for floating-point numbers, that is, the part of the real numbers that are representable in the computer. The reason is that the encodings of integer and float values in the computer are different, and that the computer has different machine instructions for adding integer values and for adding float values, for example.