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3.2.18 The src/tree Directory

Namespace tree, delivered for TC-5. The implementation of the intermediate representation. The file tree/README should give enough explanations to understand how it works.

Reading the corresponding explanations in Appel’s book is mandatory.

It is worth noting that contrary to A. Appel, just as we did for ast, we use n-ary structures. For instance, where Appel uses a binary seq, we have an n-ary seq which allows us to put as many statements as we want.

To avoid gratuitous name clashes, what Appel denotes exp is denoted sxp (Statement Expression), implemented in translate::Sxp.

Please, pay extra attention to the fact that there are temp::Temp used to create unique temporaries (similar to misc::symbol), and tree::Temp which is the intermediate representation instruction denoting a temporary (hence a tree::Temp needs a temp::Temp). Similarly, on the one hand, there is temp::Label which is used to create unique labels, and on the other hand there are tree::Label which is the IR statement to define to a label, and tree::Name used to refer to a label (typically, a tree::Jump needs a tree::Name which in turn needs a temp::Label).

File: fragment.* (src/tree/)

It implements tree::Fragment, an abstract class, tree::DataFrag to store the literal strings, and tree::ProcFrag to store the routines.

File: fragments.* (src/tree/)

Lists of tree::Fragment.

File: visitor.* (src/tree/)

Implementation of tree::Visitor and tree::ConstVisitor to implement function objects on tree::Fragments. In other words, these visitors implement polymorphic operations on tree::Fragment.