(guile.info.gz) Symbol Read Syntax
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21.6.6 Extended Read Syntax for Symbols
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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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