Syntax for Cool Objects

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Syntax for Cool Objects

Every Cool value is an object. Objects contain a list of named attributes, a bit like records in C. In addition, each object belongs to a class. We use the following syntax for values in Cool:

$v = X(a_{1} = l_{1}, a_{2} = l_{2}, \dots , a_{n} = l_{n})$

Read the syntax as follows: The value $v$ is a member of class $X$ containing the attributes $a_1, \ldots, a_n$ whose locations are $l_1, \ldots, l_n$ . Note that the attributes have an associated location. Intuitively this means that there is some space in memory reserved for each attribute. The value $v$ has dynamic type $X$ .

For base objects of Cool (i.e., $\tt Int$ s, $\tt String$ s, and $\tt Bool$ s) we use a special case of the above syntax. Base objects have a class name, but their attributes are not like attributes of normal classes, because they cannot be modified. Therefore, we describe base objects using the following syntax:

$\begin{array}{l} Int(5) \\ Bool(true) \\ String(4,{\tt"Cool"}) \end{array}$

For $\tt Int$ s and $\tt Bool$ s, the meaning is obvious. $\tt String$ s contain two parts, the length and the actual sequence of ASCII characters.

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