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5 points by rocketnia 5921 days ago | link | parent

If you need to use the particular name "." and you're not worried about brevity, you can input the symbol like this:

  arc> (coerce "." 'sym)
  |.|
  arc> '|.|
  |.|
  arc> (is '|.| (coerce "." 'sym))
  t
It's the same as escaping the symbols |(|, |)|, |'|, |"|, etc. These characters have special meaning to the reader, so they're less convenient to use in symbols.

As for . specifically, it's special to the reader because of dotted lists:

  arc> (nthcdr 3 '(a b c . terminator))
  terminator
Also, as long as . is already special, MzScheme overloads it for a kind of infix-like syntax sugar, which Arc inherits:

  arc> '(a b c . <- . x y z)
  (<- a b c x y z)
A reader could probably be smart enough to interpret "'." as being equivalent to "'|.|", but this one doesn't go to that trouble. I don't blame it, either. As long as . means something special to the reader in one symbol-like place, and as long as MzScheme is going to use it for other things like infix syntax, it might as well be treated as a reserved word.


1 point by anoni 5920 days ago | link

Good point. I ran into the same problem with |, but it's not a big deal if I have to use different symbols.

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