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class Continuation
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Parent:
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Object
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Version:
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1.6
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Index:
call
Continuation objects are generated by
Kernel#callcc
. They hold a return address and execution
context, allowing a nonlocal return to the end of the callcc
block from anywhere within a program. Continuations are somewhat
analogous to a structured version of C's setjmp/longjmp
(although they contain more state, so you might consider them closer
to threads).
For instance:
arr = [ "Freddie", "Herbie", "Ron", "Max", "Ringo" ]
callcc{|$cc|}
puts(message = arr.shift)
$cc.call unless message =~ /Max/
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produces:
This (somewhat contrived) example allows the inner loop to abandon
processing early:
callcc {|cont|
for i in 0..4
print "\n#{i}: "
for j in i*5...(i+1)*5
cont.call() if j == 17
printf "%3d", j
end
end
}
print "\n"
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produces:
0: 0 1 2 3 4
1: 5 6 7 8 9
2: 10 11 12 13 14
3: 15 16
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instance methods
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call
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cont.call( [
args
]*
)
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Invokes the continuation. The program continues from the end of
the callcc block. If no arguments are given, the original
callcc returns nil. If one argument is given,
callcc returns it. Otherwise, an array containing
args is returned.
callcc {|cont| cont.call }
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nil
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callcc {|cont| cont.call 1 }
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1
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callcc {|cont| cont.call 1, 2, 3 }
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[1, 2, 3]
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