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Guile Reference Manual

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21.7.3 Keyword Read Syntax

Guile, by default, only recognizes the keyword syntax specified by R5RS. A token of the form #:NAME, where NAME has the same syntax as a Scheme symbol (see section 21.6.6 Extended Read Syntax for Symbols), is the external representation of the keyword named NAME. Keyword objects print using this syntax as well, so values containing keyword objects can be read back into Guile. When used in an expression, keywords are self-quoting objects.

If the keyword read option is set to 'prefix, Guile also recognizes the alternative read syntax :NAME. Otherwise, tokens of the form :NAME are read as symbols, as required by R5RS.

To enable and disable the alternative non-R5RS keyword syntax, you use the read-set! procedure documented in 33.3.2 User Level Options Interfaces and 33.3.3 Reader options.

 
(read-set! keywords 'prefix)

#:type
=>
#:type

:type
=>
#:type

(read-set! keywords #f)

#:type
=>
#:type

:type
-|
ERROR: In expression :type:
ERROR: Unbound variable: :type
ABORT: (unbound-variable)


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