4.2 Values and Types

Up to now we have seen several values used in Oz: numbers, atoms, records, and lists. There are more values and types in Oz. A still incomplete list of values and types is the following:

• A number is either an integer or a float (rational number).

• An atom is a word.

• A Boolean value is either true or false.

• The unit is a constant value without particular meaning (a dummy).

• A record is an atom or a term of the form Lab(F1:V1 ... Fn:Vn) where:

  • .

  • the label Lab is an atom, the unit, or a Boolean.

  • the features F1, ... , Fn are pairwise distinct atoms or integers.

  • the fields V1, ..., Vn are arbitrary values.

• A tuple is a record with only integer features.

• A list is a tuple which is either the atom nil or a tuple |(1:V 2:L) where | is an atom, V a value, and L a list. The atom | is sometimes called `cons'.

• A string "hiho" is a list of ASCII characters, i.e integers between 0 and 128.

• A procedure is a value.