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Colon in Scheme

(show-data 'YHOO :config 'my-config)

I saw some Scheme code (in Guile) like the line above and get confused with the colon syntax :config .

What kind of language features of this? Is it a intrinsic feature of Scheme, or specially designed for the Guile lib? How does it work? I kept searching this online but still found nothing. Thanks.

Solution

  • It's a keyword and its purpose is to make the invocation of a procedure that receives optional arguments easier and convenient.

    You can read more about this feature in this section of the Guile Reference Manual.