(guile.info.gz) Symbol Read Syntax

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 21.6.6 Extended Read Syntax for Symbols
 ---------------------------------------
 
 The read syntax for a symbol is a sequence of letters, digits, and
 "extended alphabetic characters", beginning with a character that
 cannot begin a number.  In addition, the special cases of `+', `-', and
 `...' are read as symbols even though numbers can begin with `+', `-'
 or `.'.
 
    Extended alphabetic characters may be used within identifiers as if
 they were letters.  The set of extended alphabetic characters is:
 
      ! $ % & * + - . / : < = > ? @ ^ _ ~
 
    In addition to the standard read syntax defined above (which is taken
 from R5RS ( Formal syntax (r5rs)Formal syntax.)), Guile provides
 an extended symbol read syntax that allows the inclusion of unusual
 characters such as space characters, newlines and parentheses.  If (for
 whatever reason) you need to write a symbol containing characters not
 mentioned above, you can do so as follows.
 
    * Begin the symbol with the characters `#{',
 
    * write the characters of the symbol and
 
    * finish the symbol with the characters `}#'.
 
    Here are a few examples of this form of read syntax.  The first
 symbol needs to use extended syntax because it contains a space
 character, the second because it contains a line break, and the last
 because it looks like a number.
 
      #{foo bar}#
 
      #{what
      ever}#
 
      #{4242}#
 
    Although Guile provides this extended read syntax for symbols,
 widespread usage of it is discouraged because it is not portable and not
 very readable.
 

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