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I have the following code:

(plot (function sin (- pi) pi #:label "y = sin(x)"))

But while solving SICP I did not encounter such a construct: #:label "y = sin(x)" What does the hash tag mean?

animuson
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1 Answers1

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It's an optional keyword argument, an optional extra argument for the function function that is passed by name. #:label is the keyword, and "y = sin(x)" is the value. All keywords have the form of a hashtag and a colon followed by the keyword name, e.g. #:label, #:foo, #:blah, etc. See Keywords in the docs.

Jack
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