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3573 :: need an explanation of strings/add behavior

• r3d9u11 (orginal) [2018-02-23T08:49:05+01:00] view original

  Hi. I'm tried to do something like a:

  var s = "str123"
  s.add(s)
  echo s
  Run

  I'm expected 'str123str123', but got 'str123str123s'. Why did appeared the last symbol 's'? What difference beetween concateration (&) and adding strings?

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• def (orginal) [2018-02-23T09:25:26+01:00] view original

  Probably because you are manipulating the string itself while coyping from it. If this should be allowed, then the code should make a copy of the original size before manipulating the target in add. Sounds like a bug that could easily be fixed.

  Edit: I don't see this behaviour in the current devel branch, so it might have been fixed or be system dependent.

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• r3d9u11 (orginal) [2018-02-23T10:47:52+01:00] view original

  Thanks for answer!

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• Libman (orginal) [2018-02-23T18:24:08+01:00] view original

  That unexplained trailing 's' character does NOT appear for me on v0.17.2, including in a local installation of Nim Playground.

  I do see it on play.nim-lang.org (which is used by this forum's "Run" button). So it's probably a bug in whatever version of Nim is used there.

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  System add...

  proc add*(x: var string, y: string) {.magic: "AppendStrStr", noSideEffect.}
  Run

  It's a proc, Jim, but not as we know it...

  It's MAGIC! :P

  From what I understand, this is done so that different code generators (C, JS, VM, etc) can do it differently.

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• darek (orginal) [2018-02-24T10:55:52+01:00] view original

  echo NimVersion on play.nim-lang.org also shows 0.17.2

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• Libman (orginal) [2018-03-06T08:53:21+01:00] view original

  Thanks for pointing that out. So we don't know what the extent of the 's' bug was, but the Playground is now at 0.18.0 and it's gone.

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