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4 points by fallintothis 5359 days ago | link | parent

First-class continuations & call/cc are notoriously difficult to explain (and indeed, can be hard to understand in code that uses them). Your best bet is to Google around for info, seeing if you can make sense of the (vast) material available. http://en.wikipedia.org/wiki/Call-with-current-continuation and http://community.schemewiki.org/?call-with-current-continuat... might be good starts.

As for point 5, Arc uses certain characters as syntax abbreviations iff the special characters occur in what would otherwise be normal symbols (to the Scheme reader). So far, there's

  .a    ; is the same as (get a)
  a.b   ; is the same as (a b)
  !a    ; is the same as (get 'a)
  a!b   ; is the same as (a 'b)
  f&g   ; is the same as (andf f g)
  f:g   ; is the same as (compose f g)
  ~f    ; is the same as (complement f)
where

  ((get a) b)        ; is the same as (b a) by Arc's indexing
                     ; e.g., ("abc" 0) is #\a
  ((andf f g) x)     ; is the same as (and (f x) (g x))
  ((compose f g) x)  ; is the same as (f (g x))
  ((complement f) x) ; is the same as (no (f x))
See arc.arc for the actual definitions of these operators.

There are precedence and associativity rules, such as

  a!b.c ; is the same as ((a 'b) c) because ! and . are 
        ; left-associative
  f:g:h ; is the same as (compose f g h)
  ~f:g  ; is the same as (compose (complement f) g)
To explore these more, you can use the ssexpand function in Arc:

  arc> (ssexpand 'a:b.c!d)
  (compose a b.c!d)
  arc> (ssexpand 'b.c!d)
  ((b c) (quote d))