COMMENT ⊗   VALID 00002 PAGES
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C00002 00002	A constituent character has one or more attributes, which define how the
C00004 ENDMK
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A constituent character has one or more attributes, which define how the
character can be interpreted by the reader.  These are {\it alphabetic},
{\it digit}, {\it package marker}, {\it plus sign}, {\it minus sign}, {\it
dot}, {\it decimal point}, {\it ratio marker}, {\it floating-point
exponent marker} and {\it illegal}.  Table 21-2 shows the standard
attributes for constituent characters.  Alphabetic constituents are those
characters that can appear in a symbol name.  Note that any character
quoted with a preceding single escape character will be treated as an
alphabetic constituent regardless of its normal syntax.

A macro character triggers special parsing of subsequent input characters.
When the reader encounters a macro character, it calls a special function
assigned to that macro character.  This function generally parses one
special-format object from the input stream and returns the constructed
object.  The macro character function can also return no values,
indicating that the characters scanned by the function are being ignored,
as in the case of a comment.