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   6 <TITLE>The SUIF Version 1 Library - Numbering Types and Symbols</TITLE>
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  17 <H2><A NAME="SEC50" HREF="suif1_toc.html#TOC50">Numbering Types and Symbols</A></H2>
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  28 Every symbol and type is assigned an ID number that uniquely identifies
  29 it within a particular context.  These ID numbers should be used to
  30 refer to symbols and types in annotations that will be written to the
  31 output files and in other situations where pointers to the symbol and
  32 type nodes cannot be used.  The <CODE>sym_id</CODE> method retrieves the ID
  33 number for a symbol, and the <CODE>type_id</CODE> method gets the number for a
  34 type.
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  39 For symbols and types within a procedure, the ID numbers are only unique
  40 within that procedure.  Similarly, the ID numbers for symbols and types
  41 in a file symbol table are only unique within that file.  Only in the
  42 global symbol table are the ID numbers truly unique.  This is
  43 implemented by dividing the ID numbers into three ranges.  Each range is
  44 reserved for a particular level in the symbol table hierarchy.  To make
  45 it easier to read an ID number, the <CODE>print_id_number</CODE> function
  46 prints it as a character to identify the range (<SAMP>`g'</SAMP> for global,
  47 <SAMP>`f'</SAMP> for file, <SAMP>`p'</SAMP> for procedure) combined with the offset of
  48 the number within that range.
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  54 The symbol and type ID numbers cannot be assigned individually, but the
  55 symbol tables provide methods to set them.  The <CODE>number_globals</CODE>
  56 method is defined in the <CODE>global_symtab</CODE> class to number the
  57 entries in global and file symbol tables, and the <CODE>number_locals</CODE>
  58 method is defined in the <CODE>proc_symtab</CODE> class to number all of the
  59 entries in the procedure symbol table and its descendents.  These
  60 methods only assign ID numbers to symbols and types that do not already
  61 have numbers.  These methods are called automatically before writing
  62 things out to files, but they can also be called whenever you want to
  63 assign numbers to new symbols and types.
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  69 The <CODE>clear_sym_id</CODE> symbol method and <CODE>clear_type_id</CODE> method
  70 are provided to reset the ID numbers to zero manually, but as far as
  71 the library itself is concerned, this is never necessary.  The library
  72 automatically changes ID numbers when necessary, such as when moving
  73 from one symbol table to another.
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