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Why does DrRacket (kind of Scheme) IDE highlights some of the identifiers as "keywords" (for example define, lambda, send*), and the others as "symbols" (user defined identifiers, +, -, abs, send, send+, etc.)?

I am particularly confused by the difference between send* and send+. For reference, here are the beginnings of their definitions:

(define-syntax (send* stx) ...

(define-syntax (send+ stx) ...

(It is possible that I do not use the terms "identifier", "symbol", and "keyword" completely correctly, but this is how some of them seem to be used in DrRacket preferences.)

Unless this is a bug, it must be explained by the language "semantics", so I decided to ask here.

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DrRacket maintains a list of keywords that it understands for auto-indentation, which you can find in the Preferences (under Editing->Indenting). If an identifier is listed as a keyword for indentation, then DrRacket will also highlight it differently if the chosen color scheme differentiates keywords from plain identifiers.

Identifiers like + are not highlighted because they are just names of functions, not "special forms" like if and cond. On the other hand, send+ isn't highlighted just because the default DrRacket keywords don't contain every syntactic form provided by Racket.

  • Is this a bug then? – Alexey Jan 6 '14 at 17:29
  • I mean, who decides which identifiers are keywords? How should i maintain the lists of keywords? – Alexey Jan 7 '14 at 22:18
  • You can add keywords yourself in the preferences. If you think it should go in the default list, you can submit a bug report or ask on the Racket mailing list. – Asumu Takikawa Jan 8 '14 at 13:53

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