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   6 <TITLE>The SUIF Version 1 Library - Symbol Table Hierarchy</TITLE>
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  17 <H2><A NAME="SEC41" HREF="suif1_toc.html#TOC41">Symbol Table Hierarchy</A></H2>
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  23 The SUIF symbol tables are organized in a hierarchy of nested scopes and
  24 maintained internally within a tree structure.  Every table contains a
  25 list of the symbol tables that are its children, and each table also has
  26 a pointer back to its parent in the tree (except for the global symbol
  27 table which does not have a parent).  The <CODE>children</CODE> method returns
  28 a pointer to the list of children and the <CODE>parent</CODE> method gets the
  29 pointer to the parent symbol table.  Thus, to search through all of the
  30 enclosing scopes, one can follow the parent pointers back to the global
  31 symbol table, visiting all of the symbol tables along the way.  The
  32 <CODE>is_ancestor</CODE> method provides an easy way to check if a given
  33 symbol table is an ancestor (i.e. an enclosing scope) of the current
  34 table.
  35
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  37 <P>
  38 Note that the symbol table hierarchy is not independent.  The primary
  39 objects in a SUIF program are the files and the abstract syntax trees
  40 for the procedures.  The symbol tables are always attached to these
  41 primary objects and are generally treated as if they are parts of those
  42 objects.  For example, when a block of code is deleted the associated
  43 symbol table is automatically removed from the hierarchy and deleted.
  44
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  47 <A NAME="IDX264"></A>
  48 The <CODE>base_symtab</CODE> class is the base class from which the other
  49 symbol table classes are derived, but it is an abstract class and cannot
  50 be used directly.  There are four different derived symbol tables
  51 classes.  They have much in common, but each is used at a different
  52 level in the hierarchy and thus has slightly different features.
  53
  54 </P>
  55
  56 <UL>
  57 <LI><A HREF="suif1_42.html#SEC42">Global Symbol Table</A>: Global scope (shared across files).
  58 <LI><A HREF="suif1_43.html#SEC43">File Symbol Tables</A>: File-level global scopes.
  59 <LI><A HREF="suif1_44.html#SEC44">Procedure Symbol Tables</A>: Top-level procedure scopes.
  60 <LI><A HREF="suif1_45.html#SEC45">Block Symbol Tables</A>: Nested scopes within procedures.
  61 </UL>
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