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6.6.8.3 Keyword Read Syntax

Guile, by default, only recognizes a keyword syntax that is compatible with R5RS. A token of the form #:NAME, where NAME has the same syntax as a Scheme symbol (see section 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.

If the keyword read option is set to 'postfix, Guile recognizes the SRFI-88 read syntax NAME: (see section SRFI-88 Keyword Objects). Otherwise, tokens of this form are read as symbols.

To enable and disable the alternative non-R5RS keyword syntax, you use the read-set! procedure documented Reading Scheme Code. Note that the prefix and postfix syntax are mutually exclusive.

(read-set! keywords 'prefix)

#:type
⇒
#:type

:type
⇒
#:type

(read-set! keywords 'postfix)

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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